الجـامعـــــــــة اإلســـــالميــة بغــــــزة The Islamic University of Gaza

عمادة البحث العلمي والدراسات العليا Deanship of Research and Graduate Studies

كـــلـــيــــــــــــة الـــهـــنـــــدســـــــة Faculty of Engineering Master of Electrical Engineering ماجستيــر الهنــدســـة الكهـــربائيـــة

Design of MIMO Antenna for Future 5G Communication Systems

تصميم هوائي متعدد المداخل ومتعدد المخارج ألنظمة اتصاالت الجيل الخامس

By Tareq H. Elhabbash

Supervised by

Dr. Talal F. Skaik Associate Professor of Electrical Engineering

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Electrical Engineering

April/2019 إقــــــــــــــرار

أنا الموقع أدناه مقدم الرسالة التي تحمل العنوان:

Design of MIMO Antenna for Future 5G Communication Systems

تصميم هوائي متعدد المداخل ومتعدد المخارج ألنظمة اتصاالت الجيل الخامس

أقر بأن ما اشتملت عليه هذه الرسالة إنما هو نتاج جهدي الخاص، باستثناء ما تمت اإلشارة إليه حيثما ورد، وأن هذه الرسالة

ككل أو أي جزء منها لم يقدم من قبل االخرين لنيل درجة أو لقب علمي أو بحثي لدى أي مؤسسة تعليمية أو بحثية أخرى.

Declaration

I understand the nature of plagiarism, and I am aware of the University’s policy on this.

The work provided in this thesis, unless otherwise referenced, is the researcher's own work, and has not been submitted by others elsewhere for any other degree or qualification.

طارق حسين الهباش :Student's name اسم الطالب: Signature: التوقيع: Tareq Date: التاريخ: 1/3/2019

I

Abstract

5G communication system is considered as a revolution in the wireless communication market where a very high bandwidth is required for modern smart phones. This fast revolution drives researchers for developing the communication technology whether in software or hardware fields. Also, antenna design is considered as a basic field which needs a continuous developing for serving 5G wireless communication systems.

The main goal of this thesis is designing a dual band, multiple-input multiple-output MIMO microstrip antenna for serving the 5G communication systems by achieving all the important features of the recent wireless communication systems. The proposed antenna is designed to operate at dual high frequencies (mm-waves) which are 28GHz and 38GHz. The 5G main features are also satisfied in the proposed design dual polarization, high bandwidth (>1 GHz) and high realized gain (>12 dBi). For enhancing the directivity and the realized gain of the antenna design, an antenna array is proposed where a two-element antenna array design and four-element antenna array design are built. The four-element array design has to achieve a high gain and high bandwidth at both bands of operation. Beam steering capability is achieved by inserting a phase shifter (transmission line) into the four element design. This modification added the ability for tilting the main radiation pattern to particular direction at the both resonant frequencies. The four element antennas (with and without the phase shifter) are used in a MIMO configurations for 5G handsets and base station with an octagonal structure.

III

ملخص الدراسة

تعتبر أنظمة اتصاالت الجيل الخامس ثورة في مجال سوق االتصاالت الالسلكية، حيث أن األجهزة الذكية تحتاج إلى نطاق واسع من الترددات. هذه الثورة السريعة دفعت الباحثين إلى تطوير تكنولوجيا االتصاالت في مجالي البرمجيات والمعدات. كما يعتبر مجال تصميم الهوائيات من المجاالت األساسية التي تحتاج إلى تطوير مستمر لخدمة أنظمة اتصاالت الجيل الخامس.

الهدف الرئيسي من هذه الرسالة هو تصميم هوائي متعدد المداخل ومتعدد المخارج يعمل على ترددين هما 82 جيجا هيرتز و 82 جيجا هيرتز ويحقق جميع الخصائص الهامة ألنظمة اتصاالت الجيل الخامس ومنها ثنائية االستقطاب وتوفير نطاق تردد واسع. الهوائي المقترح في هذه الرسالة صمم لكي يعمل على الترددات العالية )موجات بطول موجي قصير يقاس بالمليمتر( ، كما وحقق هذا التصميم ثنائية االستقطاب ونطاق ترددي أكبر من 1 جيجا وبكسب أكبر من 18 ديسيبل. ومن منطلق العمل على تحسين اإلتجاهية وكسب الهوائي فقد تم تصميم هوائي على شكل مصفوفة مكونة من عنصرين وذلك الستخدامه في لوحات األجهزة الذكية وتصميم هوائي على شكل مصفوفة مكونة من أربعة عناصر وذلك الستخدامه في تصميم محطة إرسال تخدم أنظمة اتصاالت الجيل الخامس. كما تم تحقيق خاصية توجيه البث من الهوائي وذلك بإضافة محول التجاه االشارة إلى التصميم الرباعي. هذا التحسين أضاف إمكانية إمالة إتجاه االشعاع الرئيسي إلتجاهات مختلفة على كال الترددين.

إن محطة اإلرسال المقترح تصميمها على شكل ثماني بحيث يحتوي كل وجه على اثنى عشر هوائي موزعة بالتساوي بين التصميم الرباعي بدون محول اإلشارة والتصميم الرباعي مع محول اإلش ارة على جهة اليمين و التصميم الرباعي مع محول اإلشارة على الجهة اليسار، وبهذا تم تحقيق معظم خصائص الجيل الخامس في محطة اإلرسال.

IV

Dedication

To

My Parents

My Wife and Children

My Brothers and Sisters

My Family

My Friends

V

Acknowledgment

I am greatly thankful to Allah for bleesing me with this successful work.

I am very grateful to my supervisor Dr. Talal Skaik who did not hesitate to help and support me to complete this work.

Great thanks for my parents where without their support I have not reached what I am now.

Special thanks for my wife for her patience and support. Many thanks for my brothers and sisters for their trust. Thanks for my family and friends.

VI

Table of Contents

Declaration ...... I

Abstract ...... III

Dedication ...... V

Acknowledgment...... VI

Table of Contents ...... VII

List of Tables ...... IX

List of Figures ...... X

List of Abbreviations ...... XIII

Chapter One: Introduction ...... 1 1.1 Introduction ...... 2 1.2 Evolution on Mobile Communication ...... 3 1.3 MIMO Technology ...... 5 1.4 Literature Review...... 7 1.5 Thesis Motivation ...... 9 1.6 Thesis Overview...... 10

Chapter Two: Antenna Theory ...... 11 2.1 Introduction ...... 12 2.2 Maxwell's equations ...... 13 2.3 Parameters of Antenna ...... 14 2.4 Type of Antenna ...... 19 2.5 Microstrip Antenna ...... 23 2.6 Feeding Methods ...... 29 2.7 Antenna Arrays ...... 32 2.8 Phase Shifters ...... 35 2.9 Summary: ...... 37

Chapter Three: Design of 5G Patch Antenna Arrays ...... 38 3.1 Introduction ...... 39 3.2 Array Feeding Techniques...... 39 3.3 Single Element Design ...... 41 3.4 Design of Antenna Array ...... 46 3.5 Four- element Antenna Array Design ...... 48 3.6 Four-element antenna array with fixed beam steering ...... 51

VII

Chapter Four: Design of 5G MIMO Antenna for Handsets and Mobile Base Stations ...... 56 4.1 Introduction ...... 57 4.2 Design of Handsets ...... 57 4.3 Design of Base Stations ...... 62 4.4 Summary ...... 67

Chapter Five: Conclusion and Future Work ...... 68 5.1 Conclusion ...... 69 5.2 Future Work ...... 70

References ...... 71

VIII

List of Tables

Table (1.1): Comparison between mobile generations ...... 5

Table (2.1): Maxwell's Equations for Statics Electromagnetic Fields ...... 13

Table (2.2): Dominant Mode ...... 27

Table (3.1): Parameters of the single patch antenna ...... 42

Table (3.2): Parameters of the two-element patch antenna ...... 48

Table (3.3): Parameters of distribution networkfor four-element array...... 49

Table (4.1): Modern smart phones sizes ...... 57

Table (4.2): Handsets comparisons ...... 62

Table (4.3): Base stations comparisons ...... 66

IX

List of Figures

Figure (1.1): MIMO system ...... 5 Figure (1.2): Space Division Multiplexing (SDM) ...... 6 Figure (1.3): Space Time Coding (STC) ...... 6 Figure (2.1): Antenna ...... 12 Figure (2.2): Antennas Thevenin Equivalent ...... 13 Figure (2.3): Type of Radiation Patterns ...... 14 Figure (2.4): HPBW & FNBW ...... 15 Figure (2.5): The spatial behavior of the electric and magnetic fields of a linearly (vertical) polarized wave for a fixed instant of time ...... 17 Figure (2.6): Type of polarization ...... 18 Figure (2.7): Antenna Bandwidth...... 18 Figure (2.8): Transmitting antenna and its equivalent circuit...... 19 Figure (2.9): Dipole Antennas...... 20 Figure (2.10): Half wave dipole antennas ...... 20 Figure (2.11): Aperture Antennas ...... 21 Figure (2.12): Reflector Antennas ...... 22 Figure (2.13): Patch Shapes ...... 23 Figure (2.14): Micro-strip line, electric field lines, and effective dielectric constant...... 25 Figure (2.15): Physical and effective length of rectangular patch ...... 26 Figure (2.16): Modes for rectangular patch antenna ...... 28 Figure (2.17): Coaxial Feed ...... 30 Figure (2.18): Micro-strip inset Feed ...... 30 Figure (2.19): Gap coupling Feed...... 31 Figure (2.20): Aperture coupling Feed...... 31 Figure (2.21): Proximity coupling Feed...... 32 Figure (2.22): Two-element infinitesimal dipole ...... 33 Figure (2.23): A switched line phase shifter ...... 36 Figure (2.24): Loaded line phase shifter – basic circuit ...... 36 Figure (2.25): A reflection phase shifter using a quadrature hybird ...... 37 Figure (3.1): Antenna Arrays...... 39 Figure (3.2): Series Feeding...... 40

X

Figure (3.3): Corporate Feeding...... 40 Figure (3.4): Series - Corporate Feeding...... 40 Figure (3.5): Single band (28 GHz) patch antenna...... 41 Figure (3.6): Slotted single element dual-band (28/38GHz) antenna...... 42

Figure (3.7): Single element single band antenna simulation result (S11)...... 43

Figure (3.8): H-Slotted single element dual-band Simulation result (S11)...... 43 Figure (3.9): Non-slotted antenna radiation pattern (Realized Gain) ...... 44 Figure (3.10): H-Slotted antenna radiation pattern at 28 GHz (Realized Gain) ...... 44 Figure (3.11): H-Slotted antenna radiation pattern at 38 GHz (Realized Gain) ...... 45 Figure (3.12): Effect of increasing the parameter d in the H-shaped slot...... 45 Figure (3.13): Effect of increasing the parameter ww in the H-shaped slot ...... 46 Figure (3.14): Two-element antenna array structure ...... 46

Figure (3.15): Two-element simulated S11 result ...... 47 Figure (3.16): Two-elememt three dimensional radiation pattern at 28 GHz (Realized Gain) ...... 47 Figure (3.17): Two-elememt three dimensional radiation pattern at 38 GHz (Realized Gain) ...... 48 Figure (3.18): Four-Element antenna array structure...... 49

Figure (3.19): A four-element simulated S11 result...... 50 Figure (3.20): A four-element three dimensional radiation pattern at 28 GHz (Realized Gain) ...... 50 Figure (3.21): A four-element three dimensional radiation pattern at 38 GHz (Realized Gain) ...... 51 Figure (3.22): A four-element antenna array structure with right phase shifter...... 52 Figure (3.23): A four-element antenna array structure with left phase shifter ...... 52

Figure (3.24): Phase shifted four-element simulated S11 result...... 53 Figure (3.25): A four-element three dimensional radiation pattern at 28 GHz (Realized Gain) (right phase shifter)...... 53 Figure (3.26): A four-element three dimensional radiation pattern at 38 GHz (Realized Gain) (left phase shifter) ...... 54 Figure (3.27): A four-element three dimensional radiation pattern at 28 GHz (Realized Gain) (right phase shifter) ...... 54

XI

Figure (3.28): A four-element three dimensional radiation pattern at 38 GHz (Realized Gain) (left phase shifter) ...... 55 Figure (4.1): MIMO technology ...... 57 Figure (4.2): Handset Design ...... 59 Figure (4.7): Top view of the base station ...... 63 Figure (4.8): Three dimensional view of the base station ...... 63 Figure (4.9): The base station's side ...... 64 Figure (4.10): Mutual coupling between arrays (Port 1 excited) ...... 65 Figure (4.11): Mutual coupling between arrays (Port 5 excited) ...... 65

XII

List of Abbreviations

1G First Generation Wireless Systems 2G Second Generation Wireless Systems 3G Third Generation Wireless Systems 4G Forth Generation Wireless Systems 5G Fifth Generation Wireless Systems AMPS Advanced Mobile Phone System B.W Bandwidth CDMA Code Division Multiple Access D-AMPS Digital Advanced Mobile Phone System DVB Digital Video Broadcasting FNBW First Null Beam-width GPRS General Packet Radio Service GSM Global System Mobile HPBW Half-Power Beam-width HSCSD High Speed Circuit Switch Data LTE Long Term Evolution MIMO Multiple Input Multiple Output MMS Multimedia Messaging Services MSA Microstrip Antenna SDM Space Division Multiplexing STC Space Time Coding TACS Total Access Communication System TDMA Time Division Multiple Access UMTS Universal Mobile Telecommunication System WCDMA Wideband Code Division Multiple Access WWWW Wireless World Wide Web

XIII

Chapter One Introduction

Chapter One Introduction

1.1 Introduction

Wireless communication systems are rapid growing systems in industry specially the cellular systems. In 2019, the number of mobile phone users in the world is 4.68 billion and it is expected to reach 4.78 billion at the end of 2020 (statista.com).

If we analyze the term wireless communication literally, we find that it consists of two words: The first is communication, which means sending and receiving different messages between two points. The second word is wireless that means there is no tangible connection between the two points of contact and the lack of cable between them. Based on the above, we can define wireless communication as a process of communication between two different points without a tangible link between them.

The early man used radio communication with the means available to him. He used smoke signals, light signals, reflective lenses, audio signals and other different communication methods However, all these old systems which were before the industrial era were suffering from the lack of distance between the various points of contact and there must be a clear line of vision between the transmitter and reciever, and therefore remained control points on the high areas in order to increase the distance of communications (Andrea Goldsmith, 2005).

In 1895, radio communication was born, where Marconi transmitted the first radio signal (electromagnetic signal) for about 18 Km, so all the early wireless communication methods were replaced by radio communication systems. The early radio communication systems used analog signals in transmitting, but nowadays most of the wireless communication systems use digital signals which are composed of binary bits (Andrea Goldsmith, 2005).

Due to this thesis we aimed to achieve all the important features of the recent wireless communication systems by designing a dual band, multiple-input multiple-output MIMO microstrip antenna for serving the 5G communication systems. The proposed antenna will designed to operate at dual high frequencies (mm-waves) which are 28GHz and 38GHz. The 5G main features have to be satisfied in the proposed design like, dual polarization, high bandwidth (>1 GHz) and high realized gain (>12 dBi).

Antenna array structures are also proposed in this thesis for enhancing the directivity and achieving the required realized gain of the antenna for the 5G communication systems. Beam steering capability will also be achieved by inserting a phase shifter (transmission line) into the final design. This proposed modification aims to add the ability for tilting the main radiation pattern to particular direction at the both resonant frequencies.

2

Finally, the final antenna designs will be used in a MIMO configurations for 5G handsets and base station.

1.2 Evolution on Mobile Communication

Mobile communication technologies have gone through several stages or generations of evolution and improvement in their performance which are divided as follows:

1.2.1 1G Communication Systems

We can call the first generation communication system as the analog generation, where the first generation of the mobile phones was analog and it was used for voice traffic only. There were many first generation communication systems in Europe like TACS (Total Access Communication System) which was located in 900 MHz frequency band with 25 kHz channel bandwidth and 2 kbps data rate. In United States of America, AMPS (Advanced Mobile Phone System) was the famous system, it was located on the 800 MHz band with 30kHz channel bandwidth and 10kbps data rate. The users of TACS and AMPS could not make a call with each other because the technologies used in the different systems are not compatible with each other (Rappaport, 2009).

1.2.2 2G Communication Systems

By transforming the communication systems from analog to digital the second generation began. In addition to voice traffic, more services are achieved like short message, data transmissions, authentication, and data encryption. GSM (Global System Mobile) is the most famous 2G communication system. It is located on 900 MHz and 1800 MHz in most parts of the world and located on 850 MHz and 1900 MHz in USA, Canada, Maxico and some of south America countries (WorldTimeZone.com). It used time division multiple access (TDMA) where the time frame is divided into eight slots per channel and used (FDMA) where the bandwidth of the channel is divided into non-overlapping sub- channels and achieved 64 kbpd data rate. There are another 2G systems like digital advanced mobile phone system (D-AMPS) in USA where it used code division multiple access (CDMA) and interim standard 95B (IS-95B) in Asia (Rappaport, 2009).

1.2.3 2.5G Communication Systems

The 1G and 2G systems used the circuit switch network scheme. In this scheme, the system established a fixed channel between transmitter and receiver, whether it was used or not, and this channel cannot be used by other callers until disconnecting the call between them. In 2.5G, an enhancment on the system had been achieved, where the packet switch network scheme had been used, which caused increasing of the data rate to 144Kbps. In this scheme, the information data is sent by a packet with addressing data. Many users can use the channel by sending their packets to the destination showing in the addressing data. There are some systems in this generation like general packet radio

3 service (GPRS), high speed circuit switch data (HSCSD) and enhancing data rate of GSM evolution (GSM). All these systems are considered as enhancing on the GSM system and as a bridging stage between 2G and 3G communication systems (Rappaport,2009).

1.2.4 3G Communication Systems

A realized revolution has been done for the previous generations, where it supports both the circuit switch network and the packet switch network and it is based on Internet Protocols (IP). This feature supports the 3G systems to be worldwide systems and increased the data rate up to 2 Mbps. Multimedia applications like video conferencing and full-motion video have been supported. Universal Mobile Telecommunication System (UMTS) is the major 3G systems. It is an evolution of the GSM system and it used wideband code division multiple access (WCDMA) standard which provides higher data rate, higher speed, and higher capacity than GSM (Rappaport,2009).

1.2.5 4G Communication Systems

Increasing the system data rate is the main goal of any enhancment for any communication systems. 4G systems offer a high data rate up to 100 Mpbs and in addition to the 3G features these new systems provide Multimedia Messaging Services (MMS), Digital Video Broadcasting (DVB) and more clarifying for watching T.V. Long Term Evolution (LTE) is the major 4G systems, it provides high quality of services (QoS), high capacity, and better data security than the previous generations (Lopa J. Vora, 2015).

1.2.6 5G Communication Systems

5G (Fifth Generation wireless systems) is a term used for wireless communication technologies which is aiming to improve the capacity of network by offering faster network and very high data rates multimedia streaming for users and it used millimeter waves (high frequencies). For serving smart phones and the 5G mobile base stations many advances have been added on antenna designs. The new 5G antennas will be operated on high frequencies and will achieve high bandwidth over 1 GHz. Improving the capacity of the wireless networks is also a main goal of 5G systems with lower cost and better coverage area. Most of the recent researchers in wireless communications field focus on the high frequencies (28 GHz/38 GHz) bands which results to small antenna sizes suitable for using in the mobile smart phones. Moreover, 5G antennas are required to achieve high gain by employing array configurations. Moreover, 5G systems will support multiple- input multiple-output (MIMO) technologies.

5G systems data rate will be higher than 1Gbps. Compared to previous generations, 5G systems provide faster data transmission, higher capacity, clarity in video and audio, and supporting interactive multimedia. The major suggested system is wireless world wide web (WWWW). Table 1 provides comparisons between mobile generations.

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Table (1.1): Comparison between mobile generations (Lopa J. Vora, 2015) Technology 1G 2G 3G 4G 5G Start Year 1970-1990 1990-2004 2004-2010 2010-2020 Soon (800- (800- Frequency 150MHz- 900)MHz 900)MHz 3GHz- 2GHz-8GHz Bands 900MHz (1800- (1600- 300GHz 1900)MHz 2000)MHz 64Kbps 100Mbps - higher than Data Rate 2Kbps 2Mbps 144Kbps 1Gbps 1Gbps UMTS, LTE, WiFi, Technology Analog Digital WWWW CDMA2000 WiMax Circuit, Switching Circuit Packet Packet Packet Packet TDMA, Multiplexing FDMA CDMA OFDM OFDM FDMA Analog Digital Data, MMS, Primary Large Phone Phone Call, Phone Calls, IP Services Services Broadcasting Calls Messages SMS

1.3 MIMO Technology

MIMO (Multiple-Input Multiple Output) is a technology that will be used in 5G mobile networks aiming to increase the capacity of the system without using an extra bandwidth where the capacity is directly proportion with the number of antennas at the transmitter or at the receiver. It achieves higher data rate with low cost, but it may increase the complexity of the system structure. A MIMO system is shown in Figure 1.1.

Figure (1.1): MIMO system

The MIMO systems can use two different transmission schemes which are,

5

1.3.1 Space Division Multiplexing (SDM)

In this scheme, every antenna in the MIMO system transmits different data streams at the same time and in parallel channels. As seen in Figure 1.2 the transmitted data is divided into sub-data streams, which is transmitted by different antennas simultaneously. At the receiving antennas, the streams are combined together for giving the original data stream. In this way, we can increase the system capacity.

Figure (1.2): Space Division Multiplexing (SDM)

1.3.2 Space Time Coding (STC)

In this scheme presented in Figure 1.3, the performance of the MIMO system is improved for achieving a diversity gain by using multiple antennas. At the receiver, the diversity gain is achieved. So, this method is suitable for systems which do not have any knowledge about the transmitter.

Figure (1.3): Space Time Coding (STC)

Any MIMO system can have a combination of SDM and STC to be able to achieve better channel capacity and/or the reliability of the communication system.

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1.4 Literature Review 1.4.1 5G MIMO Antenna  A compact wideband MIMO antenna has been presented in (Wang, Duan, Li, Wei and Gong, 2017). Its operation band covers from 3 GHz to 30 GHz. In this paper, there are two designs. The first one is without slots and its S11 shows -20 dB and less at the range from 5 GHz to 10 GHz, and the most deep value is -45 dB at 8 GHz. The second one is with slots and its S11 shows A -20 dB and less at the range from 3 GHz to 18 GHz, and the deepest value is -55 dB at 5.5 GHz. In the paper, a single element antenna had been designed. Multiple-element antenna is not addressed.  A dual band MIMO antenna for 5G handsets has been presented in (Dioum, Diop, Sane, Khouma and Diallo, 2017). The operation frequencies are 2.6 GHZ and 3.6 GHz. The single element antenna has a suitable size for handsets and its S11 shows about -15 dB at 2.65 GHZ and 3.75 GHz. The MIMO antenna has 4 elements and its S11 shows a deep value equal to -80 dB at 2.8 GHz. In this paper only a single element antenna had been designed.  A dual polarized cavity-backed aperture antenna for 5G MIMO applications has been presented in (Liu, Hsu and Lin, 2015). The operation band is around 30 GHz. The structure of antenna is a combination of rectangular antenna and tapered slot

antenna. The S11 shows -25 dB on the range from 25 GHz to 36 GHz. However, in this paper the designed antenna has a complex structure and it is not easy to fabricate. The proposed designs in this thesis are microstrip-based and they are easy to fabricate.  A compact tapered slot antenna array for 5G millimeter wave massive MIMO system has been presented in (Yang, Yu, Dong, Zhou, and Hong, 2016). The system has a good beam-forming performance because the space between array elements meets the requirement of half wavelength. The operation band of antenna array is from 22.5 GHz to 32 GHz. The S11 is -10 dB along the operation band and the deep value of it is about -35 dB which is from 25 GHz to 30 GHz. In this paper, the antenna size is about 6 cm and it cannot be used for mobile handset.

1.4.2 5G Antennas for Handsets

 An end-fire phased array antenna has been presented in (Parchin, Shen and Pedersen, 2016). The single element antenna has leaf bow-tie shape and it served the (28 GHz, 38 GHz) bands. Its S11 is -20 dB at 28 GHz and -30 dB at 38 GHz. The MIMO antenna has eight elements of leaf shaped bow-tie antenna which form a linear phased array. In this paper, 9-11 dBi gain was achieved.  A compact MIMO antenna system has been presented in (Thomas, Veeraswamy and Charishma, 2015). There are two antenna elements employed in the system. The first one has rectangular shape and the second has circular shape. The

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combination of these two antennas serves a group of frequencies (1.50 GHz, 2.2 GHz and 28 GHz). A single band PIFA antenna has been presented in (Haraz, Ashraf and Alshebeili, 2015). It has three rectangular shape elements located at the same line and separated by an equal distance between there centers. The antenna serves 28 GHz frequency and its S11 is -25 dB at this frequency. The peak gain of it is 6.06 dBi. This designed is served single band only and array structure has not be used. The proposed antenna design in this thesis uses the array structure and serves dual bands.  A dual band MIMO antenna with folded structure for 5G mobile handsets has been presented in (Shi, Zhang, Xu, Liu, Wen and Wang, 2017). The antenna consists of 8 elements located on the orthogonal frame corner of substrate. The operation bands are (3.4 GHz – 3.6 GHz) and (4.55 GHz – 4.75 GHz) and its S11 is -35dB at the first range and -25dB at the second one. In this design, they used short neutral line to reduce the mutual coupling at both bands. In this paper, the array structure is not used and also their design does not support higher 5G frequencies (28 GHz).  An eight port dual polarized MIMO antenna for 5G smartphone applications has been presented in (Li, Xu, Ban, Yang and zhou, 2016). The operation band is (2.55 GHz-2.65 GHz). The antenna has a simple structure where the single elements of it has a square shape hollow from inside and the boarder width equal to 2mm. Its S11 is -35 dB at 2.6 GHz. In this paper, only a single element antenna has been designed and it also does not support higher 5G frequencies (28 GHz).  A dual band antenna array with a circular polarization and beam steering capability features has been presented in (Mahmoud and Montaser, 2018). Its operation bands are 28 GHz and 38 GHz. The single element consists from three copper layers where the middle layer has T-shape feeding line every substrate layer has a hole for aperture feeding. This single elements used in a 12 element array for a mobile handset where they were divided equally on top, right and left sides of the mobile. However, the fabrication of this design in not easy compared with the proposed antenna design in this thesis.

1.4.3 5G Antennas for base stations

 A compact millimeter wave massive MIMO has been presented in (Ali and Sebak, 2016). Its S11 is -17 dB at 28 GHz and -28 dB at 38 GHz. At 28/38 GHz the gain value is more than 12 dBi at each band. Antenna elements are distributed in space for massive MIMO base station architecture with a radius of 25 mm. Total beams scanning of 360° is achieved by 12 switched elements.  A massive MIMO 5G small cell antenna with high isolation has been presented in (Liao, Chen and Sim, 2017). The operation band is (3.4 GHz – 3.6 GHz) and the cell has 8-ports. The single element has T-shaped bars which result to good isolation between the closed ports. However, the does not support operation at higher 5G frequencies such as 28 GHz.

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 A 5G phased patch antenna array for mobile base station has been presented in (Ishfaq, Abd Rahman, Yamada and Sakakibara, 2017). Its Operation frequency is 28 GHz. The array consists from 8-elements connected by series fed technique. The base station also consists from 8 arrays, so the total number of elements is 64. The proposed antenna in this thesis serves dual band operation and used corporate feed technique which gives the ability to control the beam direction.  A conical frustum array antenna of multi polarization has been presented in (Mahmoud and Montaser, 2018). 5G dual bands had been served by the base station (28,38 GHz). Its 32-element array antenna had been distributed in conical frustum configuration and it achieved 8.17 dBi gain. However, the base station design does not support MIMO technology.  A triple band indoor base station with dual polarization has been presented in (Alieldin, Huang, Boyes, Stanley, Joseph, Hua and Lei, 2018). This base station is proposed for the 1G, 2G, 3G, 4G and 5G (sub-6 GHz) applications. The proposed antenna used in this base station consists from three types of dipoles where each type served one band. The fabrication of the antenna structure is not easy also the shortage of the bandwidth at sub-6 GHz causes reduction of the data rate of the system.  A 5G massive MIMO antenna system for a triangular 72- port base station with switched beam steering feature has been presented in (Al-Tarifi, Sharawi and Shamim, 2018). The base station dimensions are 120x60 cm. Every single port consists from 2x2 patch antenna array. The antenna consists from three metallic layers, the top one has the patches, the middle one is the ground layer and the bottom one has the feeding networks. The probe feed techniques used in the design.

1.5 Thesis Motivation

The 5G communications system is promising to achieve high data rates and low latency. This allows fast video streaming and connectivity between end users. To this end, researchers and engineering teams worldwide are developing technologies that satisfy the 5G requirements. The main goal of this thesis is serving the 5G communication systems by designing new microstrip antennas which achieve all the important features of the recent wireless communication systems likes MIMO configuration, high data rate, dual band, dual polarization,… etc. The proposed antenna is designed to operate at 5G high frequencies bands.

The proposed microstrip antenna will be used in a proposed handset with close size to the modern handsets and MIMO configuration will be achieved. Moreover, it will be used in building a proposed 5G base station with a beam steering capability.

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1.6 Thesis Overview

Chapter 1 contains a brief background on the fifth generation of wireless communication systems. A summary on the 5G important features and frequency bands is presented. Also, a short literature review for many papers talking about the 5G antenna designs for mobile smart phones and base stations is presented.

Chapter 2 explains the theoretical part of antenna parameters. It describes the main antenna parameters which are the radiation pattern and its types, the directivity and gain, the beam-width, antenna polarization, antenna efficiency and input impedance. Also, the classification of the antenna depending on the physical structure will be explained. Moreover, design procedure of microstrip antennas will be shown.

Chapter 3 presents the proposed designs of the patch antenna for 5G systems. Firstly, it explains the array concepts and the feed methods, then explains the patch designs. The designs are separated into two parts: the first one is the basic without using the array concept. The second part consists many array designs where we have two-element antenna array and four-element antenna array. Also a phase shifter is added to the four- element antenna array for achieving beam steering ability to the design.

Chapter 4 introduces the proposed design employing the MIMO concept in the 5G communication systems. The design of antenna array for handsets and for 5G octagonal base station will be presented.

Chapter 5 presents the conclusions with a brief of the most important results and proposed future work to enhance the current results.

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Chapter Two Antenna Theory

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Chapter Two Antenna Theory

2.1 Introduction

An antenna or an Aerial is defined as a metallic device which converts the electrical signals to electromagnetic waves and vise-versa as shown in Figure (2.1). It can work as a transmitter or as a receiver. Also it can be defined as the transitional structure between a guiding device and the free-space (Balanis ,3th edition, 2015).

Figure (2.1): Antenna (Balanis ,3th edition, 2015)

Without antenna, there is no wireless communications, so it is considered as an important part in wireless systems. The size and the shape of antennas vary depending on their operations frequencies and applications.

As shown in Figure (2.2), the antenna systems can be represented in Thevenin equivalent circuit, where an ideal generator represents the source, a line with characteristic impedance ZC represents the transmission line, and a load ZA represents the antenna where,

ZA = [ ( RL + Rr) + jXA] 2.1

 RL: conduction and dielectric losses  Rr: radiation resistance  XA: the imaginary part of the impedance

In this ideal case, we aim to transform all the source energy to the radiation resistance (Balanis ,3th edition, 2015).

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Figure (2.2): Antennas Thevenin Equivalent (Balanis ,3th edition, 2015)

2.2 Maxwell's equations

Maxwell's equations are a set of equations, as shown in table (2.1), that describe the behavior of electromagnetic waves (Sadiku, 2001). James Clerk Maxwell, scientist in mathematical physics field, unified a set of physics laws and experimental results into a set of equations knows as Maxwell's equations. These equations can be used as the basic for studying electricity and magnetism (Andre Waser, 2000).

Table (2.1): Maxwell's Equations for Statics Electromagnetic Fields (Sadiku 3th edition, 2007)

# Differential From Integral From Remarks

1 훻 . 퐷 = 휌푣 ∮ 퐷 . 푑푆 = ∫ 휌푣 푑푣 Gauss's law 푆 푣 Nonexistence of 2 훻 . 퐵 = 0 ∮ 퐵 . 푑푆 = 0 푆 magnetic monopole 휕퐵 휕 Conservativeness of 3 훻 × 퐸 = − ∮ 퐸 . 푑푙 = − ∫ 퐵. 푑푆 휕푡 퐿 휕푡 푆 electrostatic field 휕퐷 휕퐷 4 훻 × 퐻 = 퐽 + ∮ 퐻 . 푑푙 = ∫ (퐽 + ). 푑푆 Ampere's law 휕푡 퐿 푆 휕푡 Where:  D: Electric Flux Density (C\m2)  B: Magnetic Flux Density (Tesla)  E: Electric Field Strength (V\m)  H: Magnetic Field Strength (A\m)  J: Current Density (A\m2)  휌: Electric Charge Density (C\m3)

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The first equation states that charge density can be defined as a source or a sink of electric flux lines and the second one states that magnetic flux does not deviate from a source point and always found in closed loops (Hayt, Buck, 6th edition, 2000). The third equation (Maxwell – Faraday equation) states that the spatially varying or time varying in the electric field accompanies a time varying magnetic field, and vice versa (Sadiku 3th edition, 2007). The relation between the electric current and the magnetic field is described by the forth equation (Ampere – Maxwell equation), where it describes the resulted magnetic field from a transmitter wire or loop (Hayt, Buck, 6th edition, 2000).

2.3 Parameters of Antenna

This section presents antenna parameters to understand and characterize the antenna performance when designing and measuring antennas.

2.3.1 Radiation Pattern The antenna radiation pattern can be defined as a graphical representation of radiated properties (power/field) as a function of the angular space. The mean of the radiated properties is the magnitude of electric or the magnetic field. When we plot the magnitude of the electric or the magnetic field we have the Field Pattern and when we plot the square of electric or the magnetic field we have the Power Pattern coordination.

The radiation pattern can be separated to various radiation lobes, where the lobe containing the direction of the maximum radiation is called the main lobe or the major lobe and the other lobes are called minor lobes (back or side lobe) as shown in Figure 2.3. Moreover, we find nulls between the lobes, where the fields goes to zero.

Figure (2.3): Type of Radiation Patterns (balanis, 2015)

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There are three major shapes of radiation patterns depending on the direction of the radiation: Isotropic: It is the radiation patterns of an ideal antenna which has equal radiation in all directions. Its shape looks like a ball. Omin-directional: It is the radiation pattern of an antenna which has equal radiations in a given plane and directional radiations in any orthogonal plane. Its shape looks like a donut. Directional: It is the radiation pattern of an antenna which has effectively radiation in some directions than other directions.

2.3.2 Beam-width

The beam-width of an antenna is the angular separation between two identical points on opposite side of the pattern maximum (Balanis ,3th edition, 2015). Many beam-widths are found in the antenna pattern but the most important one is the Half-Power Beam- width (HPBW). HPBW contains the direction of the maximum of the antenna beam, and it is defined as the angle between the two identical points in which the radiation intensity in one-half value of the beam. There is another important beam-width which is the First Null Beam- width (FNBW) that is defined as the angular separation between the first nulls of the patterns (Balanis ,3th edition, 2015). See Figure (2.4).

Figure (2.4): HPBW & FNBW (balanis, 2015)

2.3.3 Directivity

The directivity is an important parameter and it is defined as the ratio of the maximum radiation intensity of designed antenna to the isotropic radiation intensity. The radiation

05 intensity (U) is the total power radiated by the designed antenna per unit solid angel. In mathematical form:

Max radiation intensity of designed antenna 퐷irectivity = Radiation intensity of isotropic antenna

U 4 ∗ 휋 ∗ U 퐷 = = 2.2 Uo Prad

 D: Directivity  U: Radiation Intensity of the designed antenna

 UO : Radiation Intensity of the isotropic antenna

 Prad: Total radiation power.

2.3.4 Antenna Efficiency

The antenna efficiency can be defined as the ratio of the output power (radiated power) of the antenna to the input power to the antenna. In mathematical form:

Radiated Power (P ) Efficiency () = rad Input power (Pinput) 2.3

Referring to (Balanis ,3th edition, 2015), the losses in the power are caused by the mismatching between the antenna and the transmission line, also losses occur in conduction and dielectric materials.

2.3.5 Gain

The antenna gain can be defined as the ratio of the radiation intensity of designed antenna to the desired direction to the isotropic radiation intensity. So it is too close to the directivity in definition but the simple difference between them is that the directivity considers the input power equals to the radiated power but the gain takes the efficiency of antenna in the calculation as shown in its mathematical expression.

( ) ( ) ( ) Gain G = (Efficiency  ) ∗ (Directivity D ) 2.4 Units for antenna gain listed are in dB, dBi or dBd. The definitions of terms are: dB – decibels. (i.e. 10 dB means 10 times the energy relative to an isotropic antenna in the peak direction of radiation). dBi - "decibels relative to an isotropic antenna". This is the same as dB. 3 dBi means twice (2x) the power relative to an isotropic antenna in the peak direction.

06 dBd - "decibels relative to a dipole antenna". Note that a half-wavelength dipole antenna has a gain of 2.15 dBi. Hence, 7.85 dBd means the peak gain is 7.85 dB higher than a dipole antenna; this is 10 dB higher than an isotropic antenna.

2.3.6 Polarization

The polarization of an electromagnetic wave follows the direction of the electric field. So, we can define the antenna polarization as the polarization of the transmitted waves from the antenna in the designed direction. The polarization of a plane wave in Figure (2.5) shows that the instantaneous electric field traces out with time at a fixed observation point (Stutzman, Thiele, 3rd edition, 2013).

Figure (2.5): The spatial behavior of the electric and magnetic fields of a linearly (vertical) polarized wave for a fixed instant of time (Stutzman, Thiele, 2013).

There are three main type of polarization,

Linear polarization: the electric field’s vector stays in the same plane and move in straight line at every instant time. It has two type of polarization (vertical and horizontal) as shown in Figure (2.6).

Circular polarization: the electric field’s vector moves in as a function of time. The field has two orthogonal components which much have the same magnitude. The effect of multi-path is reduced so it is used in the satellite communication. It has two type of polarization (left-hand circular polarizations and right-hand circular polarization ) as shown in Figure (2.6).

Elliptical polarization: It is the same as the circular polarization but the magnitudes of the two orthogonal components of the field are not the same. So, we can see that the linear and the circular polarization can be considered as a special case of the Elliptical polarization. It has two type of polarization (left-hand elliptical polarizations and right- hand elliptical polarization ) as shown in Figure (2.6).

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Figure (2.6): Type of polarization (Stutzman, Thiele, 3rd edition, 2013).

2.3.7 Band-width

The antenna bandwidth (B.W.) can be defined as the range of frequencies on the two sides of the resonant frequency of the antenna where the values of all the antenna parameter are acceptable like (Gain, Input impedance, Polarization, …etc.) and its usually taken under -10 dB value of the scattering parameter (S11) as shown in Figure (2.7)

Figure (2.7): Antenna Bandwidth.

2.3.8 Input Impedance

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The input impedance of an antenna can be defined as the ratio of the voltage to the current between two terminals or it is the impedance between the antenna terminals, where the antenna can be modeled as a an equivalent electrical circuit as shown in Figure (2.8).

Figure (2.8): Transmitting antenna and its equivalent circuit.

The mathematical form of the input impedance (Balanis ,3th edition, 2015):

ZA = RA + jXA 2.5

Where:  ZA = antenna impedance at terminals a and b (ohms)  RA = antenna resistance at terminals a and b (ohms)  XA = antenna reactance at terminals a and b (ohms)

RA = Rr + RL 2.6 Where:  Rr = radiation resistance of the antenna  RL = loss resistance of the antenna

2.4 Type of Antenna

We can classify the antenna types depending on physical structure into,

2.4.1 Wire Antenna

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Wire antennas are considered as the oldest and the most prevalent type of antenna. It is made from solid wire or tubular conductor and it easy to construct and cheaper than other types of antennas. There are different type of wire antenna like dipole (straight line), loop (circular or ellipse) and helix.

2.4.2 Folded Dipole

It’s a closed wire antenna and it provides good matching to coaxial lines. It's most widely length is about half wavelength. As shown in figure (2.9) a,b and c.

Figure (2.9): Dipole Antennas.

2.4.3 Half wave dipole

A dipole antenna is classified depending on the value of its length. The most famous type of dipole antenna is the half wave dipole antenna as shown in Figure (2.10). Its length equals to a half wavelength (depends on its operation frequency). Its matching to the transmission line is easy where its radiation resistance (73 ohm) is near to the characteristics impedance of transmission lines (50 ohm or 75 ohm).

Figure (2.10): Half wave dipole antennas (Balanis ,3th edition, 2015).

2.4.4 Aperture Antenna

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Aperture antennas are used often at UHF frequencies and in applications with high gain. Its gain increases with square of frequency at constant efficiency of antenna. We can classify the this type of antenna to two parts which are the horn and the waveguide as shown in figure 2.11

Figure (2.11): Aperture Antennas

2.4.5 Reflector Antenna

The usage of this type of antenna started in the Second World War and it was used in the radar application and the space communication. Nowadays, it is used in our houses for reception of TV signals from satellites. The concept of the reflector antenna is not converting the electrical signals to electromagnetic waves or vice versa but on focusing the electromagnetic waves to a focus point. The structural configuration of the reflector antenna controls the radiation parameters of it like antenna pattern, polarization and efficiency. It has some famous shapes; the first shape is the plane shape is the simplest one, it is used to control the direction and the polarization of the wave, the second shape is the corner antenna, it consists from two plane antennas with an angle between them and it has deferent type depending on the value of the corner angle (60,90,120,..ect) , the third shape of reflector antenna is the parabolic shape which works on focusing the signal on a focal point, it consists from the vertex (Symmetrical point on its surface) and the fed source. Figure (2.12) shows different types of reflector antennas.

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Figure (2.12): Reflector Antennas (Balanis 2015).

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2.5 Microstrip Antenna

Microstrip antenna (MSA) has different names like patch antenna and printed antenna. This type of antenna is becoming popular within mobile applications because it can be printed directly on the circuit board. Patch antennas are easily fabricated and have low cost. Microstrip antenna consists of three parts. The first one is the radiating patch which is made from metal and suspended over the dielectric substrate which is the second part of the MSA. The last part is the ground plane which is made from the same metal of the patch layer and is suspended under the substrate. The size of the patch antenna is inversely proportional to its operating frequency. This feature increased the popularity of it especially in 5G wireless communication application where the bands of frequencies are very high (in Giga Hertz). So, the size of antenna is small (in millimeter). The radiation part of the Micro-strip antenna (Patch) has many different shapes as shown in Figure 2.13

Figure (2.13): Patch Shapes

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2.5.1 Advantages and limitations of MSA

There are many advantages and limitations for microstrip antenna when comparing it with other antenna types:

Advantages:  Light weight, small size and has a thin shape.  Easy and inexpensive to fabricate.  It can conform easily to surfaces (low profile).  Its feeding methods are easy.  It can be used in array shape easily when combining with phase shifter we have smart antennas.  It supports linear and circular polarization.  One patch can support dual and triple resonant frequencies.  It allows for additional tuning elements like pins or varactor diodes.

Limitations:  Limited Bandwidth.  Low efficiency.  Used only with high frequencies (microwave), because its size will be too large at low frequencies.  Low power handling capacity.

2.5.2 Methods of analysis

For the analysis of microstrip antenna, we have several methods. The most popular methods are transmission-line mode, cavity mode and the full wave mode. The transmission line method is the simplest one but it is the less accurate. On the other side, the full wave method is very accurate with highest complexity. The cavity model is on the mid-point between the other two methods in accuracy and complexity. Here we will talk about these three methods for the rectangular patch shape.

2.5.2.1 The transmission line method

In this model, the rectangular patch antenna can be represented as two radiating narrow slots with width (W) and height (h) separated by distance (L). Since there are two different dielectric (air, substrate), the micro-strip line is considered as a nonhomogeneous line of these dielectrics. There is an effective dielectric constant εreff because the large amount of the waves traveling in the substrate and the remaining waves travel in air. This means that there is a homogeneous medium with εreff replaces the substrate and the air. The mathematical form of effective dielectric constant is:

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휖 + 1 휖 − 1 ℎ −1/2 휖 = 푟 + 푟 [ 1 + 12 ] 푟푒푓푓 2 2 푊 2.7

Where:  W = patch width  h = substrate height

Figure (2.14): Micro-strip line, electric field lines, and effective dielectric constant.

Because of the fringing effects, the physical dimensions of the patch are smaller than its electrical dimensions, where the length of the patch extended on each end by ∆L as shown in Figure 2.15.

푊 ∆퐿 (휖푟푒푓푓 + 0.3)( + 0.264) = 0.412 ℎ , 푊 2.8 ℎ (휖 − 0.258)( + 0.8) 푟푒푓푓 ℎ

퐿 = 퐿 + 2∆퐿. 푒푓푓 2.9

So, the resonant frequency for the dominant TM010 mode will be: 1 푣0 (푓푟)010 = = , 2.10 2퐿푒푓푓 √휖푒푓푓√휇0휖0 2(퐿 + 2∆퐿)√휖푒푓푓

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where 8  v0 = 3*10

Figure (2.15): Physical and effective length of rectangular patch (Balanis 2015)

2.5.2.2 Cavity Mode

In this mode, the dielectric substrate interior region is modeled as a cavity bounded by a box. This box has electric walls on its top and bottom faces and has magnetic walls on its sides. The following mathematical form represents the resonant frequencies for the cavity,

1 푚휋 2 푛휋 2 푝휋 2 (푓푟)푚푛푝 = √( ) + ( ) + ( ) , 2.11 2휋√휇휖 ℎ ℎ ℎ

where:  m = the number of the variation of the half-cycle field along x direction.  n = the number of the variation of the half-cycle field along y direction.  p = the number of the variation of the half-cycle field along z direction.

The following table determines the value of the dominant mode (where the resonant frequency is the lowest) for all patch antennas which have a large enough length and

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width compared to the substrate height and figure 2.16 shows the rectangular patch antenna modes.

Table (2.2): Dominant Mode

# Condition Dominant Mode Resonant Frequency

1 푣0 (푓푟)010 = = 1 L > W > h TM010 2퐿√휇휖 2퐿√휖푟

1 푣0 2 L > W > L/2 > h TM001 (푓푟)001 = = 2푊√휇휖 2푊√휖푟

1 푣0 3 L > L/2> W > h TM020 (푓푟)020 = = 퐿√휇휖 퐿√휖푟

1 푣0 4 W > L > h TM001 (푓푟)001 = = 2푊√휇휖 2푊√휖푟

1 푣0 5 W > W/2 > L > H TM002 (푓푟)002 = = 푊√휇휖 푊√휖푟

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Figure (2.16): Modes for rectangular patch antenna (Balanis 2015)

2.5.2.3 Full wave mode

It is the extremely accurate mode where it can treat all the shape of elements (single, arbitrary, arrays, …etc.) but on the other side it is the most complex mode.

2.5.3 Rectangular patch antenna design

For designing the patch antenna we should follow these steps:

1. Determine the substrate that we want to use in our design and thus we know the substrate height (h) and the dielectric constant (εr). 2. Determine the target frequency (fr). 3. Calculate the width of the patch antenna

1 2 푣0 2 푊 = √ = √ 2.12 2 푓푟√휇0휖0 휖푟 + 1 2푓푟 휖푟 + 1

where:  v0 = light velocity in a free space.  εr = dielectric constant of the used substrate.

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 Calculate the effective dielectric constant,

휖 + 1 휖 − 1 ℎ −1/2 휖 = 푟 + 푟 [ 1 + 12 ] 2.13 푟푒푓푓 2 2 푊

 Calculate the incremental length which is caused by the fringing field,

푊 ∆ 퐿 (휖푟푒푓푓 + 0.3)( + 0.264) 2.14 ∆퐿: = 0.412 ℎ 푊 ℎ (휖 − 0.258)( + 0.8) 푟푒푓푓 ℎ

 Calculate the effective length,

푐 퐿푒푓푓 = 2.15 2푓푟√휀푒푓푓

 Calculate the patch length,

2.16 퐿 = 퐿푒푓푓 − 2∆퐿

 Use any simulation program for antenna designing like FHSS, ADS or CST.

2.6 Feeding Methods

To feed the microstrip antenna, there are many methods that can be used. These methods can be classified into two main categories which are the contacting and non-contacting. The contacting category means that the feed line is contacted to the radiating patch directly. The most popular contacting methods are the coaxial feeding and the micro-strip line. In the non-contacting category the feeding methods depend on electromagnetic feeding, where there is no direct connection between the radiating patch and the feed line. Its most popular methods are the aperture coupling, gap-coupling, and the proximity coupled feed.

2.6.1 The contacting feeding methods 2.6.1.1 Coaxial feeding

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The coaxial cable has two metal parts, the inner conductor and the outer one. In this method, we connect the inner conductor to the radiating patch and the outer one to the ground plane by drilling the substrate at a significant point to achieve the impedance matching. It is a simple method but it becomes difficult to fabricate with arrays. It also has matching problems with a thicker substrate as shown in figure 2.17.

Figure (2.17): Coaxial Feed

2.6.1.2 Microstrip inset feed line

The microstrip feed line and the radiating patch are designed on the same layer of the microstrip antenna. The strip line width is much smaller than the patch width. This method is easy to implement and to achieve impedance matching, but with increasing thickness of substrate the spurious feed radiation increases which causes limiting bandwidth as shown in figure 2.18.

Figure (2.18): Micro-strip inset Feed (balanis 2015)

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2.6.2 Non-contacting feed methods 2.6.2.1 Gap coupled feed

The feed line and the patch are at the same layer but without direct connect. There is a gap between the feed line and the patch. It has a good bandwidth but need more accuracy in fabrication as shown in figure 2.19.

Figure (2.19): Gap coupling Feed.

2.6.2.2 Aperture coupling feed

The microstrip antenna with aperture coupling feed has two different substrates with ground plane between them. The ground plane has an aperture. The radiating patch lies on the upper side of the micro-strip antenna and the transmission line lies on the bottom. This method in not easy to fabricate and also increases the antenna thickness as shown in figure (2.20).

Figure (2.20): Aperture coupling Feed.

2.6.2.3 Proximity coupling feed

Like the aperture method, it has two different substrates but with transmission line in the middle. The radiation patch is on the upper side of the micro-strip antenna and the ground

30 is on the bottom. This method reduces the spurious feed radiation and increases the bandwidth also the impedance matching can be achieved by controlling the feed line length. Its major disadvantages are the increasing of the antenna thickness and the difficulty of implementation as shown in figure 2.21.

Figure (2.21): Proximity coupling Feed.

2.7 Antenna Arrays

The radiation patterns of single-element antennas are relatively wide. This means that they have relatively low directivity. For enhancing the directivity, we can enlarge the dimensions of the single-element antenna. Another way to enhancing the directivity is by assembly of radiating elements in a proper electrical and geometrical configuration to form antenna array. The array elements are usually identical. This is not necessary but it is simpler and practical for fabrication and design (Balanis 2015).

For providing very directive pattern, it is necessary that the partial fields (generated by the individual elements) interfere constructively in the desired direction and interfere destructively in the remaining space. Also, Arrays can provide the capability of a steerable beam (radiation direction change).

2.7.1 Two-element array:

Let us assume that the antenna under investigation is an array of two infinitesimal horizontal dipoles positioned along the z-axis as shown in figure (2.22)

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Figure (2.22): Two-element infinitesimal dipole

The total field radiated by the two elements, assuming no coupling between the elements, is equal to the sum of the two and in the y-z plane it is given by:

퐸푡 = 퐸1 + 퐸2

푘 퐼 푙 푒−푗[푘푟1−(훽⁄2)] 푒−푗[푘푟21−(훽⁄2)] 0 2.17 = 푎휃푗 휂 { cos 휃1 + cos 휃2} 4휋 푟1 푟2

where β is the difference in phase excitation between the elements. The magnitude excitation of the radiators is identical.

푗(훽⁄2) 퐼1 = 퐼0푒 2.18

푗(훽⁄2) 퐼2 = 퐼0푒 2.19

For sampling the total electric field let's assume the following for far field:

 For phase variations:

휃1 = 휃2 = 휃 2.20

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푑 푟 = 푟 − cos 휃 2.21 1 2 푑 푟 = 푟 + cos 휃 2.22 2 2

 For amplitude variations:

푟1 = 푟2 = 푟 2.23

So, the total electric field become:

−푗푘푟 푘 퐼0푙 푒 1 퐸 = 푎 푗 휂 cos 휃 { 2 cos[ (푘푑 cos 휃 + 훽)]} 2.24 푡 휃 4휋푟 2

The total field of the array is equal to the field of a single element positioned at the origin multiplied by a factor which is widely referred to as the Array Factor. Thus for the two- element array of constant amplitude, the array factor is given by:

1 퐴퐹 = 2 cos [ ( 푘푑 cos 휃 + 훽)] 2.25 2

By varying the separation d and/or the phase β between the elements, the characteristics of the array factor and of the total field of the array can be controlled.

2.7.2 N-element uniform linear array:

Uniform array is an array of identical elements all of identical magnitude and each with a progressive phase. Assume that N isotropic elements have identical amplitudes but each succeeding element has a β progressive phase by which the current in each element leads the current of the preceding element.

푗훽 푗2훽 푗(푁−1)훽 퐼1 = 퐼0 , 퐼2 = 퐼0 푒 , 퐼3 = 퐼0 푒 , . . ., 퐼푁 = 퐼0 푒

The total field can be formed by multiplying the array factor by the field of a single element. This is the pattern multiplication rule and it applies only for arrays of identical elements. The array factor for the far field can be formed by:

푁 퐴퐹 = ∑ 푒푗(푛−1)휑 2.26 푛=1

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휑 = 푘푑 cos 휃 + 훽 2.27

2.8 Phase Shifters

A phase shift module is a microwave network module which provides a controllable phase shift of the radio frequency signal. It is used in phased arrays. Applications include controlling the relative phase of each element in a phase array antenna in a RADAR or steerable communications link and in cancelation loops used in high linearity amplifiers.

Next subsections present different types of common phase shifters. In the current work, a simple transmission line is added to the antenna array feeding working to achive a specific phase shift to realize fixed beam steering capability.

2.8.1 PIN diode phase shifter:

PIN diode switching elements can be used for constructed many types of microwave phase shifters (pozar 2nd edition, 1998). Diode phase shifters have the advantages of high speed and small size. There are basically three types of PIN diode phase shifters:

2.8.1.1 Switched line:

The switched line phase shifter used two single pole double throw switches to route the signal between one of two transmission lines of different length as shown in figure (2.23). The differential phase shift between the two paths is:

∆∅ = 훽(퐿2 − 퐿1) 2.28

Where 훽 is the propagation constant of the line. This phase shifter implies a true time delay between the input and the output ports. Also, it can be used for both receive and transmit functions. The switched line phase shifter is designed for binary phase shifter of ∆∅ = 180, 90, 45, … degree.

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Figure (2.23): A switched line phase shifter

2.8.1.2 The loaded line phase shifter:

It is useful for small amount of phase shifter (generally 45 degree or less). Figure (2.24) shows the basic principle of this type where the reflection and the transmission coefficient can be written by:

퐽푏 훤 = − 2.29 2 + 퐽푏

푇 = 1 + 훤 2.30

Where b = BZ0 is the normalized susceptance and the differential phase shift is:

푏 ∆∅ = tan−1 2.31 2

Figure (2.24): Loaded line phase shifter – basic circuit

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2.8.1.3 The reflection phase shifter:

This type of phase shifter used SPST (single pole single throw) switch to control the path length of a reflected signal. For providing two port circuit, a quadrature hybrid is usually used as shown in figure 2.25

Figure (2.25): A reflection phase shifter using a quadrature hybird

In operation, the input signal is divided equally among the two ports of the hybrid. The diodes are both biased in the same state, so the reflected waves from the two terminations will add at the indicated output port. Turning the diodes on or off will change the total path length and will provida phase shift at the output.

2.9 Summary:

In this chapter, antenna theory has been presented. In more details, the parameters of antenna and the antenna types have been discussed. Also, the microstrip antenna, its features, designs equations, and feed methods have been shown. In addition to that, the antenna array, beam-steering concept, and the phase shifters types have been presented.

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Chapter Three

Design of 5G Patch Antenna Arrays

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Chapter Three Design of 5G Patch Antenna Arrays

3.1 Introduction

Gain and directivity are important antenna parameters where the antennas are designed to transmit and receive signals in a designed direction. The single-element patch antenna has a relatively wide radiation pattern which means low gain and low directivity and hence single-element antenna will not satisfy the requirement of high gain in 5G systems. So, for enhancing the microstrip patch antenna an antenna array is designed and presented here. Antenna array is a collection of single-antenna elements which are connected together and work as one antenna. Increasing the number of single elements causes increasing the antenna gain and the directivity. It is not necessary to connect identical elements together to confirm antenna array but it is preferred for having easier fabrication. Antenna arrays have different types depending on the physical distribution of the single elements as shown in Figure (3.1)(Talal Skaik, 2016),

 Linear array: where the single elements are positioned along a straight line  Planar array: where the single elements are positioned on a plane.  Conformal array: where the single elements are positioned on a curved surface.

Figure (3.1): Antenna Arrays.

3.2 Array Feeding Techniques

The distribution feeding network for the patch antenna array has different feeding techniques,

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3.2.1 Series Feeding As Shown in Figure 3.2, the single elements of the patch antenna array are fed by single feed line where each patch feeds from the previous one. So, any change in any patch affects directly on the performance of the other. Also series feeding technique is applied for planar and linear arrays (balanis, 2005).

Figure (3.2): Series Feeding.

3.2.2 Corporate (Parallel) Feeding As shown in Figure 3.3, the single elements are fed by multiple lines providing a distribution network which gives power splits of n2 (where n is the number of distribution stages). Also more control of the phase and magnitude can be achieved because of the ability of changing the feeding lines lengths separately. This means that corporate feed array can have gear-steering capability for the antenna radiation patterns.

Figure (3.3): Corporate Feeding.

3.2.3 Series - Corporate Feeding It is a mixture of the two previous methods as shown in figure (3.4).

Figure (3.4): Series - Corporate Feeding.

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3.3 Single Element Design

To design a rectangular patch antenna for the application of the 5G communication system we follow the design procedure presented in Chapter 2. We first choose the substrate and determine the resonant frequencies and then calculate the antenna dimensions. This antenna is designed using low loss Teflon Based RT/duriod 5880 substrate. The dielectric constant of the used substrate is equal to 2.2 and its thickness is equal to 0.381 mm.

3.3.1 Single element antenna without slots In this design, we focus on the 28 GHz single band antenna, and later a slot will be added to the patch to operate the antenna on another band (38 GHz). A gap coupled feed line is used in the design to achieve matching with improvement in antenna bandwidth. Figure (3.5) shows the single element patch antenna without slots and Table 1 shows the dimensions of the antenna.

Figure (3.5): Single band (28 GHz) patch antenna.

3.3.2 H-Shape slotted single element To achieve dual-band operation for the micro-strip patch antenna for 5G communication system, an H-Shaped slot has been made on the patch. The outer dimensions of the H- shaped slot are almost equal to the dimensions of 38 GHz patch antenna designed on the same substrate. Figure (3.6) shows the dual-band slotted single element and Table 3.1 presents all the dimensions of the slotted antenna.

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Figure (3.6): Slotted single element dual-band (28/38GHz) antenna.

Table (3.1): Parameters of the single patch antenna # Parameter Dimension (mm) 1 W 4.18 2 L 3.6 3 ww 3.2 4 ll 3 5 y 1.8 6 wy 0.05 7 wf 1.179 8 s 0.0616 9 s2 0.049 10 d 0.8

3.3.3 Simulation results of a single patch element

Using the CST Microwave Studio Software, this antenna has been designed. As shown in the simulated result for the single band single element the magnitude of the S11 parameter has good result which equals to -36 dB at 28 GHz (Figure 3.7) with large -10 dB bandwidth of 1.3 GHz. Also, Figure (3.8) shows a good simulated result for the H-

Slotted single element at both the resonant frequencies where the magnitude of the S11

42 parameter is equal to -24 dB at 28 GHz and -27 dB at 38 GHz with -10 dB bandwidth equal about 0.8 GHz at both frequencies.

Figure (3.7): Single element single band antenna simulation result (S11).

Figure (3.8): H-Slotted single element dual-band Simulation result (S11).

The three dimensional radiation pattern for the single element single band (28 GHz) is shown in Figure (3.9). Moreover, the three dimensional patterns of the H-slotted dual- band antenna at frequencies 28 GHz and 38 GHz are shown in Figures (3.10) and (3.11) respectively. The maximum realized gain for the non-slotted patch is 7.15 dBi and for the H-slotted is 7.58 dBi at 28 GHz and 6.27 at 38GHz.

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Figure (3.9): Non-slotted antenna radiation pattern (Realized Gain)

Figure (3.10): H-Slotted antenna radiation pattern at 28 GHz (Realized Gain)

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Figure (3.11): H-Slotted antenna radiation pattern at 38 GHz (Realized Gain)

By investigating the effect of changing the H-slot shape on the scattering parameter S11 and the resonant frequencies, we found that increasing parameter d caused increasing the distance between the resonant frequencies as shown in figure (3102). Moreover, increasing the parameter ww caused decreasing of the distance between the resonant frequencies as shown in figure (3103).

Figure (3.12): Effect of increasing the parameter d in the H-shaped slot.

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Figure (3.13): Effect of increasing the parameter ww in the H-shaped slot.

3.4 Design of Antenna Array 3.4.1 Two element antenna array design

Basing on the slotted single-element design shown in figure (3.5), a two-element antenna array is designed to improve the directivity and gain of the slotted antenna at both resonant frequencies. For achieving the matching, we used quarter-wavelength transformer in the feeding network also used the parallel feeding method as shown in Figure (3.14). The dimensions of transmission lines in feeding network are presented in Table 3.2.

Figure (3.14): Two-element antenna array structure

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3.4.2 Simulation results of two patch elements

After optimizing the feeding network dimensions, the simulated result of S11 shows good matching at the two resonant frequencies which is -20 dB at 28 GHz and -22 dB at 38 GHz as depicted in Figure (3.15). Also, the three dimensional simulated radiation patterns at 28 GHz and 38 GHz show good realized gains of 9.15 dBi and 10.6 dBi respectively as shown in Figure (3.16) and Figure (3.17).

Figure (3.15): Two-element simulated S11 result

Figure (3.16): Two-elememt three dimensional radiation pattern at 28 GHz (Realized Gain)

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Figure (3.17): Two-elememt three dimensional radiation pattern at 38 GHz (Realized Gain)

Table (3.2): Parameters of the two-element patch antenna # Parameter Dimension (mm)

1 wf 1.179

2 wf70 0.8

3.5 Four- element Antenna Array Design

For satisfying 5G wireless system requirements, we have to increase the antenna gain over 12 dBi. So, a four element patch antenna array is designed based on the slotted single element (Figure 3.5). The antenna elements are fed using a parallel feeding network where quarter-wavelength transformers are used. The structure of the four elements array antenna is shown in Figure (3.18) and the distribution parameters values are shown in Table 3.3.

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Figure (3.18): Four-Element antenna array structure.

Table (3.3): Parameters of distribution networkfor four-element array. # Parameter Dimension (mm)

1 wf 1.179

2 wf70 0.8

3 wff70 0.8

4 wfff 0.35

3.5.1 Simulation results of four-element array

After optimizing the feeding network dimensions, the simulated result of S11 shows a good matching at the two resonant frequencies which is -24 dB at 28 GHz and -27 dB at 38 Ghz (Figure 3.19). Also, the three dimensional simulated radiation patterns at 28 GHz and 38 GHz show good realized gain of 12.6 dBi and 13 dBi, respectively as shown in Figure (3.20) and Figure (3.21).

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Figure (3.19): A four-element simulated S11 result.

Figure (3.20): A four-element three dimensional radiation pattern at 28 GHz (Realized Gain)

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Figure (3.21): A four-element three dimensional radiation pattern at 38 GHz (Realized Gain)

3.6 Four-element antenna array with fixed beam steering

The direction of the antenna radiation pattern is also very important in the antenna design, where the 5G systems require antennas with a beam steering capability. Higher directivity means narrower radiation beams so we have to be able to control the main beam direction. Beam steering feature of the antennas for 5G systems can be achieved by many methods that depend on changing the phase or the magnitude of the input signal to the antenna. This will change the direction of the main beam to a desired direction according to the phase difference between the signals feeding the antennas. Figures 3.22 and 3.23 present the structure of phase shifted four-element antenna array where the phase shifter was added once on the right side and another on the left side. Those two structures can achieve fixed beam steering capability where one can direct main beam to θ direction and the other structure directs the beam to -θ direction.

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Figure (3.22): A four-element antenna array structure with right phase shifter.

Figure (3.23): A four-element antenna array structure with left phase shifter

3.6.1 Simulation results of four-element array with fixed beam steering After adding the phase shifter to the four element design, the simulated result of S11 shows good matching at the two resonant frequencies which is -28 dB at 28 GHz and -23 dB at 38 Ghz Figure (3.24). Also, the three dimensional simulated radiation pattern at 28 GHz shows a good realized gain of 11.8 dBi where the beam is steered to θ = +10 degree in the structure with right phase shifter and to θ = -10 degree in the structure with left phase shifter as shown in Figures (3.25) and (3.26). Similarly, the three dimensional simulated

52 radiation pattern at 38 GHz shows a good realized gain equal of 10.5 dBi where the beam is steered to θ = +10 degree in the structure with right phase shifter and to θ = -10 degree in the structure with left phase shifter as shown in Figures (3.27) and (3.28).

Figure (3.24): Phase shifted four-element simulated S11 result.

Figure (3.25): A four-element three dimensional radiation pattern at 28 GHz (Realized Gain) (right phase shifter).

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Figure (3.26): A four-element three dimensional radiation pattern at 38 GHz (Realized Gain) (left phase shifter)

Figure (3.27): A four-element three dimensional radiation pattern at 28 GHz (Realized Gain) (right phase shifter)

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Figure (3.28): A four-element three dimensional radiation pattern at 38 GHz (Realized Gain) (left phase shifter)

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Chapter Four Design of 5G MIMO Antenna for Handsets and Mobile Base Stations

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Chapter Four Design of 5G MIMO Antenna for Handsets and Mobile Base Stations

4.1 Introduction

MIMO technology is a shortcut to Multi-input Multi-output technology, as shown in Figure (4.1). This technology is used in wireless communication systems for increasing the data rate and the system's capacity. MIMO technology also improves the quality of services of the communication systems. The bandwidth of the antenna must support the wireless systems for transmitting large data rates. Also, we have to take into consideration the mutual coupling between antennas for designing an effective MIMO system.

Figure (4.1): MIMO technology (Arnd Sibila, 2016)

The main idea of this technology is to transmit or receive different data streams by using various antennas at the same carrier signal without more power. When the antenna is transmitting its electromagnetic wave (data stream) then the wave takes different paths because of scattering environment (multipath propagation). So, in simple way we can define MIMO as the using of more than one antenna at the same time.

4.2 Design of Handsets

A quick review on the dimensions of the modern mobile smart phones has been done as shown in Table 4.1. Also, after reviewing some of recent papers on antenna design field; the dimensions of our handset design have been chosen as 110x55 mm.

Table (4.1): Modern smart phones sizes

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# Mobile Type Width (cm) Length (cm) 1 Galaxy S7 7 14.2 2 Galaxy S7 edge 7.3 15.1 3 Galaxy S8 6.8 14.9 4 Galaxy S8 Plus 6.7 16 5 Iphone 6S 6.7 13.8 6 Iphone SE 5.9 12.4 7 Iphone 7 6.7 13.8 8 Iphone 7 Plus 7.8 15.8 9 Iphone 8 6.7 13.8 10 Iphone 8 Plus 7.8 15.8 11 Pixel 2 7 14.6 12 Pixel 2 XL 7.7 15.8 13 One Plus 3T 7.5 15.3 14 One Plus 5T 7.5 15.6 15 LG G6 7.2 14.9 16 LGV30 7.5 15.2 17 BLV Dash 6.3 12.4 18 HTC U11 7.6 15.4

Here, we have used 4-element antenna arrays in the handset design as depicted in Figure 4.2. The design has four arrays, two of them are put on the upper horizontal edge of the handset and the other two arrays are put on the right vertical edge of the handset with suitable distances between the patches.

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Figure (4.2): Handset Design

The distribution of the antenna gave the dual polarization feature to the design where the patches on the horizontal size served the vertical polarization and the side patches served the horizontal polarization. Also the proposed structure supports MIMO technology, and also achieves dual-band operation, sufficient gain (>10 dBi) and sufficient bandwidth (>1 GHz). Hence, the proposed antenna design is a good candidate for handsets for 5G communication systems.

Figures (4.3) to (4.6) show the simulation of mutual coupling results between the ports of the antennas. The nearest ports to each other are port 1 and port 2 and the mutual coupling simulated result between them is better than -30 dB. Generally in this design, the distances between the arrays in the MIMO configuration are suitable and all the simulated mutual coupling results are acceptable and better than -30 dB as noticed from the graphs.

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Figure (4.3): Mutual coupling between arrays (Port 1 excited)

Figure (4.4): Mutual coupling between arrays (Port 2 excited)

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Figure (4.5): Mutual coupling between arrays (Port 3 excited)

Figure (4.6): Mutual coupling between arrays (Port 4 excited)

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Table 4.2 summarizes comparisons between the proposed handset design in this thesis and designs were submitted in other research papers.

Table (4.2): Handsets comparisons

Shi, Zhang, Thomas, Haraz, Parchin, Xu, Li, Xu, Mahmoud Mobile This Veeraswamy Ashraf Shen and Liu, Ban, Yang and Papers Thesis and and Pedersen Wen and zhou, Montaser Charishma Alshebeili and Wang

Publish 2019 2016 2015 2015 2017 2016 2018 year

Dual Triple Band Dual Band Dual Band Single Band Single Dual Band Frequencies 1.5GHz - 28GHz - 28GHz - Band 3.5GHz Band 28GHz - Bands 2.2GHz - 38GHz 38GHz 28GHz - 2.6GHz 38GHz 28GHz 4.6GHz

MIMO Yes Yes Yes Yes Yes Yes Yes

Number of 4 16 2 3 8 8 12 Ports

Dual Dual Dual Polarization Polarization Polarization Polarization Single Single Single Circular (Vertical & (Vertical & (Vertical & Horizontal) Horizontal) Horizontal)

Realized 12-13 dBi 9-11 dBi 6-7 dBi 6 dBi - - 16.85 dBi Gain

Mobile Size 10.26 * 6.8 * 5.5 * 11 6.5 * 13 4 * 12 6.8 * 13.6 5.5 * 11 (cm) 20.26 13.6

4.3 Design of Base Stations

The 4-element antenna array presented earlier is now used for building an octagonal prism structure base station for serving the 5G communication systems by achieving MIMO feature for improving the quality of the communication links. The distribution of the

62 antennas are identical for all the eight sides of base station. Figure (4.7) presents a top view for the antenna and Figure (4.8) presents a three-dimensional view of the proposed base station.

Figure (4.7): Top view of the base station

Figure (4.8): Three dimensional view of the base station

Each side of the base station has twelve 4-element antenna arrays where the three designs of 4-element antenna have been used (without phase shifter, with right phase shifter and with left phase shifter). The arrays with phase shifters are inserted into the design to achieve fixed beam steering capability for the proposed 5G station. Figure (4.9) presents the distribution of the arrays on a single side that has dimensions of 16 cm x 12.2 cm. The

63 numbers on the Figure (4.9) represent the ports’ numbers. The cuts on the vertical edges on the base station sides are for physically allowing to connect the coaxial cable connectors. Dual polarization feature is taken into account where the three designs are placed on the four edges of the base station side. The antenna arrays placed on the vertical edges enable the base station to operate with horizontal polarization and the horizontal edges enable it to operate with vertical polarization. The arrays with right and left phase shifters allow tilting the main beams by angles of 9 and -9 degrees at 28 GHz, respectively and allow tilting the main beams by angles of 10 and -10 degrees at 38GHz, respectively.

Figure (4.9): The base station's side

The simulation results of the mutual couplings between the ports are shown in Figures (4.10) and (4.11). We should note that not all mutual coupling results are shown in the graphs due to identical results for arrays with same distance between ports. Figure (4.10) presents mutual coupling results when port 1 is excited. The coupling coefficients S21, S51, S61, S91, and S10,1 are shown. Here the nearest ports are considered and the coupling to other ports is not shown due to symmetry. Similarly, mutual couplings when port 5 is

64 excited are shown in Figure (4.11). All the mutual coupling simulated results are better than -20 dB, so the distances between the antenna arrays are suitable.

Figure (4.10): Mutual coupling between arrays (Port 1 excited)

Figure (4.11): Mutual coupling between arrays (Port 5 excited)

Table 4.3 summarizes comparisons between the proposed base station design in this thesis and designs were submitted in other research papers.

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Table (4.3): Base stations comparisons:

Ishfaq, Abd Al-Tarifi, Liao, Mahmoud Base Station Ali and Rahman, Sharawi This Thesis Chen and and Papers Sebak Yamada and and Sim Montaser Sakakibara Shamim

Publish year 2019 2016 2017 2017 2018 2018

Triple Band Dual Band Dual Band Single Single Frequencies Single Band 28GHz - 28GHz - 28GHz - Band Band Bands 28GHz 38GHz - 38GHz 38GHz 3.5GHz 3.5GHz 48GHz Number of antenna per 12 1 1 8 4 24 side Number of base station 8 12 8 1 8 3 sides

Dual Polarization Polarization Single Single Single circular Single (Vertical & Horizontal)

Realized 12 - 12.5 12-13 dBi 5 dBi 24.4 dBi 7.7-8.39 dBi 19.5 dBi Gain dBi

0.15 * base station 12.2 * 16 * 3 * 7.2 * 5 * 1.3 * 2 3 * 3 * 2.4 4.1 * 5.5 29.6 * size (cm) 22.6 12.14 44.4

Steering Yes No No No No Yes Capability

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4.4 Summary

In this chapter, a proposed antenna design of modern handset has been presented. The MIMO concept is taken into consideration also other features of the 5G communication systems like dual band, dual polarization and suitable size of the smartphones had been achieved. In addition to that, a proposed octagonal 5G base station has been presented. This base station has 96 sub-array patch antennas and it achieves total beam scanning of 360 degree. Its size is suitable for 5G systems and the beam steering capability had has been achieved.

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Chapter Five Conclusion and Future Work

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Chapter 5 Conclusion and Future Work

5.1 Conclusion

Using CST simulation program, a new design of dual band dual polarization micro-strip antenna array has been designed for serving 5G wireless communication systems. The antenna operates at the frequencies 28 GHz and 38 GHz and its size is less than 2.4 cm.

An H-shaped slot has been used in the single patch antenna for achieving the dual band feature, where the proposed design achieved good gain at the two resonant frequencies. The array configuration is used for enhancing the gain and the directivity of the antenna because for the 5G communication systems the gain of the antenna have to be more than 12dBi. This gain has been achieved in the four-element antenna array design where the gain is more than 12 dBi at the two resonant frequencies.

After that we look for achieving more features for the 5G communication system, so we add a phase shifter to the four element design to achieve the beam steering feature. We designed two phased four-element configurations where the right phase shifter in first configuration causes shifting for the main beam with angle +10 toward x-axis and the left phase shifter in the second configuration causes shifting for the main beam with angle - 10 toward the x-axis.

The bandwidth of the four-element design is more than 1.5 GHz at both the resonant frequencies and the mutual coupling results at both are below -20 dB.

A dual band, dual polarization antenna is designed for smart phone devices has been designed using the four-element antenna array design. The device board dimensions are 5.5 x 11 cm which is less than most of the modern smart phone and all the simulation results are good in terms of mutual coupling (less than -25 dB) which mean that our antenna design can be suitable for the 5G smart phone.

A dual band, dual polarization 5G octagonal base station has been designed where it covers eight sectors. Every face of the base station has twelve four-element antenna arrays and the mutual coupling between any pair of it is less than -20 dB. The designed base station achieved many features like MIMO configuration, good realized gain, high bandwidth and fixed beam switching. So, it is an excellent base station for the 5G communication systems.

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5.2 Future Work

 Fabricating for all of the following designs, and comparing the simulated and measurements results o Single element antenna without slots o H-shaped slotted single element antenna o Two element antenna array o Four element antenna array o Phase shifted four element antenna arrays o Handsets board o Mobile base station  Designing and calculating the effect of the human head on the radiation pattern on the handset antennas using CST simulation program  Designing phase shifted two element antenna array  Designing new patch antennas serving 5G communication systems

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