DOCSLIB.ORG

Profile Wide Scan Angle Phased Array Antenna

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

DEVELOPMENT OF AN ULTRA-WIDEBAND LOW- PROFILE WIDE SCAN ANGLE PHASED ARRAY ANTENNA DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Henry H. Vo, B.S., M.S. Graduate Program in Electrical and Computer Engineering The Ohio State University 2015 Dissertation Committee: Prof. Chi-Chih Chen, Advisor Prof. John Volakis, Co-Advisor Prof. Joel T. Johnson © Copyright by Henry H. Vo 2015 Abstract Coupling in phased arrays is a major issue. Mutual coupling causes both gain and bandwidth reduction. Such coupling arises from the presence of adjacent elements that produce scattering and losses during low-angle beam steering. The scattering effect is comprised of (1) structural scattering and (2) antenna-mode coupling and associated losses. Losses occur when the coupled energy received by adjacent elements is dissipated at the back-end loads, resulting in lower gain at wide scan angles. In addition, the interference from periodic nature of large arrays or feed networks may produce undesired scattering modes and traveling waves that limit the upper bound of the operational frequency and maximum scan angle in ultra-wideband (UWB) arrays. As a result, current ultra wideband (UWB) array designs typically have limited scanning to no more than 45° from normal. In this dissertation, we examine the low angle scanning issues. These issues are verified via full-wave simulation. Our studies show that mutual coupling in the H-plane is stronger than in the E-plane, likely due to the dipole element pattern shape. Another focus of this dissertation is the development of an UWB dual- polarization and low angle beam steering array based on the concept of tightly coupled ii dipole arrays. For this array, we suppress/minimize mutual coupling by redesigning the antenna element, feed geometry, and array structure. Some key design parameters include (1) the simple feed of tightly-coupled dipoles, (2) array height above ground plane, (3) dielectric superstrate, and (4) parasitic coupling ring. The common mode issue is avoided by retaining the ground plane height to less than λmid/4 and the array unit cell size to 0.45λhigh. The final design is also fabricatable on a low-cost PCB. The PCB uses (1) 0.35 mils thick copper corresponding to a standard ¼ oz. copper lamination, (2) 2 mils coupling slot width and plated-thru vias manufacturable using standard PCB process, and (3) standard Roger RT/Ruroid 5880LZ substrate with dielectric constant of 1.96 and Roger RT/Duroid 5880 superstrate with dielectric constant of 2.2. An 18x18 prototype array is fabricated and measured to verify the final design. The total array height of the fabricated prototype is 0.122λ at the lowest operating frequency. It is also demonstrated that the fabricated array is capable of scanning down to more than 60° in the E- and H-planes with impedance bandwidth of 2.62:1 subject to VSWR ≤ 2. Good agreement was also observed between simulations and measurements. iii Dedication Dedicated to my family iv Acknowledgements I dedicate this dissertation to my parents, my sisters, and my brothers, for their hard work and constant support throughout my education. Without their support, I would not have what I have today. I am thankful to my advisor, Dr. Chi-Chih Chen for his support, encouragement, guidance, and endless patience throughout my time and work at the ElectroScience Lab (ESL). I thank him for sharing of his expertise and teaching me the key points of antenna design, antenna miniaturization, and as well as antenna measurement. It is my honor to have such an outstanding advisor and to be his research group member. I would also like to thank my co-advisor, Dr. John Volakis for the advice and motivation I have received from him. Thanks Dr. Joel Johnson for his valuable suggestions on this dissertation and for his participating on all my examination committee. Very special thanks go to Dr. Teh-Hong Lee for his friendship and providing me all the valuable information in antenna measurement. I would like to express my very special thanks to Patricia Toothman for her endless support, advice, and guidance. Thanks to all my friends at ESL for their friendships and insightful discussions in research as well as in course-work. v Vita December 31, 1974………………………….….…. Born – Quang Nam, Vietnam 2002……………………………………………….. B.S. Electrical Engineering, Cal Poly State University 2008……………………………………………..… M.S. Electrical Engineering, Cal Poly State University 2004-2006…………………………………………. Microwave Engineer, L-3 Com/Randtron Antenna Systems 2006-2009…………………………………………. R&D Engineer, Space Systems/Loral 2009-2011…………………………………………. Sr. R&D Engineer, Space Systems/Loral 2011-present………………………………………. Graduate Research Associate, The Ohio State University Publications H. H. Vo and C.C. Chen, “A Very Low-Profile UWB Phased Array Antenna Design for Supporting Wide Angle Beam Steering,” in review. H. H. Vo and C.C. Chen, “Frequency and Scan Angle Limitations in UWB Phased Array,” European Conference on Antenna and Propagation (EUCAP), Hague, Netherlands, Apr. 2014. H. H. Vo and C.C. Chen, “Causes of Low Scanning Angle Issues in Phased Array Antennas,” Antennas Measurement Technique Association (AMTA), Columbus, OH, Oct. 2013. vi N. K. Host, H. H. Vo, and C.C. Chen, “Causes of Low Scanning Angle Issues in Phased Array Antennas,” Antennas and Propagation Society International Symposium, Orlando, FL, Jul. 2013. Fields of Study Major Field: Electrical and Computer Engineering Studies in: Electromagnetics Microwave/Antenna Design and Measurement RF Circuits vii Table of Contents Abstract ............................................................................................................................................ ii Dedication ....................................................................................................................................... iv Acknowledgements .......................................................................................................................... v Vita.................................................................................................................................................. vi Table of Contents .......................................................................................................................... viii List of Tables ................................................................................................................................... x List of Figures ................................................................................................................................. xi Chapter 1: Introduction .................................................................................................................... 1 Chapter 2: Wide-Angle Scanning and Bandwidth Issues/Limitations of Phased Array Antennas .. 6 2.1 Mutual Coupling in Phased Arrays ........................................................................................ 6 2.2 Low-Angle Scanning Issues ................................................................................................... 7 2.2.1 Antenna Structure Mode Scattering Issue ....................................................................... 9 2.2.2 Absorption by Adjacent Elements ................................................................................ 11 2.2.3 Antenna Mode Scattering ............................................................................................. 13 2.3 Bandwidth and Wide Scan Angle Limitations ..................................................................... 15 2.3.1 Lattice Scattering Mode in Scatter Array ..................................................................... 15 2.3.2 Lattice Scattering Mode in Phased Arrays .................................................................... 18 Chapter 3: Development of Wide Scan Angle Phased Array ........................................................ 26 3.1 Revisiting TCDA Operational Principles............................................................................. 27 viii 3.1.1 Ground Plane Effect in Ideal TCD Array ..................................................................... 28 3.2 Wide Scan Angle Array Design Procedure .......................................................................... 33 3.2.1 Tightly-Coupled Array Element Design ....................................................................... 33 3.2.2 Feeding Lines ................................................................................................................ 36 3.2.3 Effect of Array Height on Wide Scan Angle ................................................................ 38 3.2.4 Effect of Element Pattern on Wide Scan Angle ............................................................ 41 3.2.5 Effect of Mutual Coupling on Wide Scan Angle .......................................................... 42 3.2.6 Effect of Parasitic Ring ................................................................................................. 46 3.3 Design Parameter Tolerance Analysis ................................................................................. 48 3.3.1 Element-to-Element Coupling Slot Width Tolerance Study ......................................... 48 3.3.2 Bonding Layer Thickness Tolerance Study .................................................................. 50 3.3.3 Feed-line Diameter Tolerance Study ...........................................................................
Recommended publications
  • Array Designs for Long-Distance Wireless Power Transmission: State

    Array Designs for Long-Distance Wireless Power Transmission: State

    INVITED PAPER Array Designs for Long-Distance Wireless Power Transmission: State-of-the-Art and Innovative Solutions A review of long-range WPT array techniques is provided with recent advances and future trends. Design techniques for transmitting antennas are developed for optimized array architectures, and synthesis issues of rectenna arrays are detailed with examples and discussions. By Andrea Massa, Member IEEE, Giacomo Oliveri, Member IEEE, Federico Viani, Member IEEE,andPaoloRocca,Member IEEE ABSTRACT | The concept of long-range wireless power trans- the state of the art for long-range wireless power transmis- mission (WPT) has been formulated shortly after the invention sion, highlighting the latest advances and innovative solutions of high power microwave amplifiers. The promise of WPT, as well as envisaging possible future trends of the research in energy transfer over large distances without the need to deploy this area. a wired electrical network, led to the development of landmark successful experiments, and provided the incentive for further KEYWORDS | Array antennas; solar power satellites; wireless research to increase the performances, efficiency, and robust- power transmission (WPT) ness of these technological solutions. In this framework, the key-role and challenges in designing transmitting and receiving antenna arrays able to guarantee high-efficiency power trans- I. INTRODUCTION fer and cost-effective deployment for the WPT system has been Long-range wireless power transmission (WPT) systems soon acknowledged. Nevertheless, owing to its intrinsic com- working in the radio-frequency (RF) range [1]–[5] are plexity, the design of WPT arrays is still an open research field currently gathering a considerable interest (Fig.
  • High Gain Isotropic Rectenna Erika Vandelle, Phi Long Doan, Do Hanh Ngan Bui, T.-P

    High Gain Isotropic Rectenna Erika Vandelle, Phi Long Doan, Do Hanh Ngan Bui, T.-P

    High gain isotropic rectenna Erika Vandelle, Phi Long Doan, Do Hanh Ngan Bui, T.-P. Vuong, Gustavo Ardila, Ke Wu, Simon Hemour To cite this version: Erika Vandelle, Phi Long Doan, Do Hanh Ngan Bui, T.-P. Vuong, Gustavo Ardila, et al.. High gain isotropic rectenna. 2017 IEEE Wireless Power Transfer Conference (WPTC), May 2017, Taipei, Taiwan. pp.54-57, 10.1109/WPT.2017.7953880. hal-01722690 HAL Id: hal-01722690 https://hal.archives-ouvertes.fr/hal-01722690 Submitted on 29 Aug 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. High Gain Isotropic Rectenna E. Vandelle1, P. L. Doan1, D.H.N. Bui1, T.P. Vuong1, G. Ardila1, K. Wu2, S. Hemour3 1 Université Grenoble Alpes, CNRS, Grenoble INP*, IMEP–LAHC, Grenoble, France 2 Polytechnique Montréal, Poly-Grames, Montreal, Quebec, Canada 3 Université de Bordeaux, IMS Bordeaux, Bordeaux Aquitaine INP, Bordeaux, France *Institute of Engineering University of Grenoble Alpes {vandeler, buido, vuongt, ardilarg}@minatec.inpg.fr [email protected] [email protected] [email protected] Abstract— This paper introduces an original strategy to step up the capacity of ambient RF energy harvesters.
  • Nested Loop Antennas This Low-Cost Five Band Loop Array Blends Into the Background

    Nested Loop Antennas This Low-Cost Five Band Loop Array Blends Into the Background

    Nested Loop Antennas This low-cost five band loop array blends into the background. G. Scott Davis, N3FJP This multi-band nested loop antenna array replaces my tribander Yagi, which is only up 20 feet. Inspired by suggestions from Bill Wisel, K3KEI, I first tried a full wave 20 meter band square loop antenna. On the air comparisons with my low Yagi confirmed instantly that this design was a hands-down winner for working both local and distant stations. I replaced that mono-band loop with a nested loop array for the 20, 17, 15, 12, and 10 meter bands. The antenna blends into the surroundings, so I needed the morning sun shining directly on it to snap the lead photo. This became a nice father-son project with my son Brad, KB3MNE. Here’s how we built the antenna. Construction We constructed the square loops shown in Figure 1 according to the dimensions in Table 1. The loops hang from a tree limb in the vertical plane. Because I feed them This stealthy nested loop is almost invisible among the trees. from the bottom corners, the loops radiate horizontal polarization. Calculate the perimeter size, P, of each holes through the pipe for the loop wire. screws into the PVC to hang the dipole loop by dividing the frequency in MHz After you run the wire through the holes, connectors seen in Figure 2. wrap a bit of electrical tape on each side of into 1005 feet. Table 1 shows the loop Matching and Feeding dimensions. Start with the 20 meter loop, the wire next to the pipe to keep the wire from sliding and to give the pipe additional Each loop antenna feed point impedance is the largest loop.
  • Arrays: the Two-Element Array

    Arrays: the Two-Element Array

    LECTURE 13: LINEAR ARRAY THEORY - PART I (Linear arrays: the two-element array. N-element array with uniform amplitude and spacing. Broad-side array. End-fire array. Phased array.) 1. Introduction Usually the radiation patterns of single-element antennas are relatively wide, i.e., they have relatively low directivity. In long distance communications, antennas with high directivity are often required. Such antennas are possible to construct by enlarging the dimensions of the radiating aperture (size much larger than ). This approach, however, may lead to the appearance of multiple side lobes. Besides, the antenna is usually large and difficult to fabricate. Another way to increase the electrical size of an antenna is to construct it as an assembly of radiating elements in a proper electrical and geometrical configuration – antenna array. Usually, the array elements are identical. This is not necessary but it is practical and simpler for design and fabrication. The individual elements may be of any type (wire dipoles, loops, apertures, etc.) The total field of an array is a vector superposition of the fields radiated by the individual elements. To provide 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. There are six factors that impact the overall antenna pattern: a) the shape of the array (linear, circular, spherical, rectangular, etc.), b) the size of the array, c) the relative placement of the elements, d) the excitation amplitude of the individual elements, e) the excitation phase of each element, f) the individual pattern of each element.
  • Vivaldi Antenna for Rf Energy Harvesting

    Vivaldi Antenna for Rf Energy Harvesting

    666 J. SCHNEIDER, M. MRNKA, J. GAMEC, ET AL., VIVALDI ANTENNA FOR RF ENERGY HARVESTING Vivaldi Antenna for RF Energy Harvesting Jan SCHNEIDER1, Michal MRNKA 2, Jan GAMEC1, Maria GAMCOVA1, Zbynek RAIDA2 1 Dept. of Electronics and Multimedia Communications, Technical University of Košice, Park Komenského 13, 041 20 Košice, Slovak Republic 2 Dept. of Radio Electronics, Brno University of Technology, Technická 12, 616 00 Brno, Czech Republic [email protected], [email protected], [email protected], [email protected], [email protected] Manuscript received November 13, 2015 Abstract. Energy harvesting is a future technology for capturing ambient energy from the environment to be recy- cled to feed low-power devices. A planar antipodal Vivaldi antenna is presented for gathering energy from GSM, WLAN, UMTS and related applications. The designed antenna has the potential to be used in energy harvesting systems. Moreover, the antenna is suitable for UWB appli- cations, because it operates according to FCC regulations (3.1–10.6 GHz). The designed antenna is printed on Fig. 1. Block diagram of the energy harvesting system. ARLON 600 substrate and operates in frequency band The antennas for energy harvesting may be divided from 0.810 GHz up to more than 12 GHz. Experimental into several categories by the operating frequency band. results show good conformity with simulated performance. The 900 MHz slot-dipole antenna on a flexible substrate was discussed in [4]. In [5], the slot-dipole antenna was improved and integrated with energy harvesting circuit. Due to the narrow-band operation and the directive radia- Keywords tion, the slot-dipole antenna harvests energy from one RF energy harvesting, UWB, Vivaldi antenna source only.
  • 1- Consider an Array of Six Elements with Element Spacing D = 3Λ/8. A

    1- Consider an Array of Six Elements with Element Spacing D = 3Λ/8. A

    1- Consider an array of six elements with element spacing d = 3 λ/8. a) Assuming all elements are driven uniformly (same phase and amplitude), calculate the null beamwidth. b) If the direction of maximum radiation is desired to be at 30 o from the array broadside direction, specify the phase distribution. c) Specify the phase distribution for achieving an end-fire radiation and calculate the null beamwidth in this case. 5- Four isotropic sources are placed along the z-axis as shown below. Assuming that the amplitudes of elements #1 and #2 are +1, and the amplitudes of #3 and #4 are -1, find: a) the array factor in simplified form b) the nulls when d = λ 2 . a) b) 1- Give the array factor for the following identical isotropic antennas with N and d. 3- Design a 7-element array along the x-axis. Specifically, determine the interelement phase shift α and the element center-to-center spacing d to point the main beam at θ =25 ° , φ =10 ° and provide the widest possible beamwidth. Ψ=x kdsincosθφα +⇒= 0 kd sin25cos10 ° °+⇒=− αα 0.4162 kd nulls at 7Ψ nnπ2 nn π 2 =±, = 1,2, ⋅⋅⋅⇒Ψnull =±7 , = 1,2,3,4,5,6 α kd2π n kd d λ α −=−7 ( =⇒= 1) 0.634 ⇒= 0.1 ⇒=− 0.264 2- Two-element uniform array of isotropic sources, positioned along the z-axis λ 4 apart is seen in the figure below. Give the array factor for this array. Find the interelement phase shift, α , so that the maximum of the array factor occurs along θ =0 ° (end-fire array).
  • Frequency Reconfigurable Vivaldi Antenna with Switched Resonators for Wireless Applications

    Frequency Reconfigurable Vivaldi Antenna with Switched Resonators for Wireless Applications

    (IJACSA) International Journal of Advanced Computer Science and Applications, Vol. 10, No. 5, 2019 Frequency Reconfigurable Vivaldi Antenna with Switched Resonators for Wireless Applications 1 4 Rabiaa Herzi , Ali Gharsallah Mohamed-Ali Boujemaa2, Fethi Choubani3 Unit of Research CSEHF Faculty of Sciences of Tunis INNOVCOM Laboratory, SUPCOM, University of El Manar, Tunis 2092, Tunisia Carthage, Tunis, Tunisia Abstract—In this paper, a frequency reconfigurable Vivaldi There are many types of frequency reconfigurable antenna with switched slot ring resonators is presented. The antennas such as switching between different narrow bands, principle of the method to reconfigure the Vivaldi antenna is wideband to notch band reconfiguration, wideband to based on the perturbation of the surface currents distribution. narrowband switching [10-11]. Switched ring resonators that act as a bandpass filter are printed in specific positions on the antenna metallization. This structure Achieving an antenna which has the capacity of wideband has the ability to reconfigurate between wideband mode and four to multi-narrow bands reconfiguration is very important and narrow-band modes which cover significant wireless essential for several applications such as a cognitive radio that applications. Combination of the bandpass filters and tapered uses wideband sensing and multi-bands communications [10, slot antenna characteristics achieve an agile antenna capable to 12, 13]. operate in UWB mode from 2 to 8 GHz and to generate multi- narrow bands at 3.5 GHz, 4GHz, 5.2 GHz, 5.5 GHz, 5.8 GHz and Because of their better radiation performances as well as 6.5 GHz. The measurement and simulation results show good Ultra-wide bandwidth, elevated gain, and compact structure agreement.
  • Class C Pool of Questions

    Class C Pool of Questions

    Class C Pool of Questions T2 1. What is the most common repeater frequency offset in the 2 meter band? T2 2. What is the national calling frequency for FM simplex operations in the 70 cm band? T2 3. What is a common repeater frequency offset in the 70 cm band? T2 4. What is an appropriate way to call another station on a repeater if you know the other station's call sign? T2 5. How should you respond to a station calling CQ? T2 6. What must an amateur operator do when making on-air transmissions to test equipment or antennas? T2 7. Which of the following is true when making a test transmission? T2 8. What is the meaning of the procedural signal “CQ”? T2 9. What brief statement is often transmitted in place of “CQ” to indicate that you are listening on a repeater? T2 10. What is a band plan, beyond the privileges established by the SMA? T2 11. Which of the following is an SMA rule regarding power levels used in the amateur bands, under normal, non-distress circumstances? T2 12. Which of the following is a guideline to use when choosing an operating frequency for calling CQ? T2B – VHF/UHF operating practices: SSB phone; FM repeater; simplex; splits and shifts; CTCSS; DTMF; tone squelch; carrier squelch; phonetics; operational problem resolution; Q signals T2 1. What is the term used to describe an amateur station that is transmitting and receiving on the same frequency? T2 2. What is the term used to describe the use of a sub-audible tone transmitted with normal voice audio to open the squelch of a receiver? T2 3.
  • Design and Analysis of Microstrip Patch Antenna Arrays

    Design and Analysis of Microstrip Patch Antenna Arrays

    Design and Analysis of Microstrip Patch Antenna Arrays Ahmed Fatthi Alsager This thesis comprises 30 ECTS credits and is a compulsory part in the Master of Science with a Major in Electrical Engineering– Communication and Signal processing. Thesis No. 1/2011 Design and Analysis of Microstrip Patch Antenna Arrays Ahmed Fatthi Alsager, [email protected] Master thesis Subject Category: Electrical Engineering– Communication and Signal processing University College of Borås School of Engineering SE‐501 90 BORÅS Telephone +46 033 435 4640 Examiner: Samir Al‐mulla, Samir.al‐[email protected] Supervisor: Samir Al‐mulla Supervisor, address: University College of Borås SE‐501 90 BORÅS Date: 2011 January Keywords: Antenna, Microstrip Antenna, Array 2 To My Parents 3 ACKNOWLEGEMENTS I would like to express my sincere gratitude to the School of Engineering in the University of Borås for the effective contribution in carrying out this thesis. My deepest appreciation is due to my teacher and supervisor Dr. Samir Al-Mulla. I would like also to thank Mr. Tomas Södergren for the assistance and support he offered to me. I would like to mention the significant help I have got from: Holders Technology Cogra Pro AB Technical Research Institute of Sweden SP I am very grateful to them for supplying the materials, manufacturing the antennas, and testing them. My heartiest thanks and deepest appreciation is due to my parents, my wife, and my brothers and sisters for standing beside me, encouraging and supporting me all the time I have been working on this thesis. Thanks to all those who assisted me in all terms and helped me to bring out this work.
  • Antenna Arrays

    Antenna Arrays

    ANTENNA ARRAYS Antennas with a given radiation pattern may be arranged in a pattern line, circle, plane, etc.) to yield a different radiation pattern. Antenna array - a configuration of multiple antennas (elements) arranged to achieve a given radiation pattern. Simple antennas can be combined to achieve desired directional effects. Individual antennas are called elements and the combination is an array Types of Arrays 1. Linear array - antenna elements arranged along a straight line. 2. Circular array - antenna elements arranged around a circular ring. 3. Planar array - antenna elements arranged over some planar surface (example - rectangular array). 4. Conformal array - antenna elements arranged to conform two some non-planar surface (such as an aircraft skin). Design Principles of Arrays There are several array design var iables which can be changed to achieve the overall array pattern design. Array Design Variables 1. General array shape (linear, circular,planar) 2. Element spacing. 3. Element excitation amplitude. 4. Element excitation phase. 5. Patterns of array elements. Types of Arrays: • Broadside: maximum radiation at right angles to main axis of antenna • End-fire: maximum radiation along the main axis of ant enna • Phased: all elements connected to source • Parasitic: some elements not connected to source: They re-radiate power from other elements. Yagi-Uda Array • Often called Yagi array • Parasitic, end-fire, unidirectional • One driven element: dipole or folded dipole • One reflector behind driven element and slightly longer
  • Army Phased Array RADAR Overview MPAR Symposium II 17-19 November 2009 National Weather Center, Oklahoma University, Norman, OK

    Army Phased Array RADAR Overview MPAR Symposium II 17-19 November 2009 National Weather Center, Oklahoma University, Norman, OK

    UNCLASSIFIED Presented by: Larry Bovino Senior Engineer RADAR and Combat ID Division Army Phased Array RADAR Overview MPAR Symposium II 17-19 November 2009 National Weather Center, Oklahoma University, Norman, OK UNCLASSIFIED UNCLASSIFIED THE OVERALL CLASSIFICATION OF THIS BRIEFING IS UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED RADAR at CERDEC § Ground Based § Counterfire § Air Surveillance § Ground Surveillance § Force Protection § Airborne § SAR § GMTI/AMTI UNCLASSIFIED UNCLASSIFIED RADAR Technology at CERDEC § Phased Arrays § Digital Arrays § Data Exploitation § Advanced Signal Processing (e.g. STAP, MIMO) § Advanced Signal Processors § VHF to THz UNCLASSIFIED UNCLASSIFIED Design Drivers and Constraints § Requirements § Operational Needs flow down to System Specifications § Platform or Mobility/Transportability § Size, Weight and Power (SWaP) § Reliability/Maintainability § Modularity, Minimize Single Point Failures § Cost/Affordability § Unit and Life Cycle UNCLASSIFIED UNCLASSIFIED RADAR Antenna Technology at Army Research Laboratory § Computational electromagnetics § In-situ antenna design & analysis § Application Examples: § Body worn antennas § Rotman lens § Wafer level antenna § Phased arrays with integrated MEMS devices § Collision avoidance radar § Metamaterials UNCLASSIFIED UNCLASSIFIED Antenna Modeling § CEM “Toolkit” requires expert users § EM Picasso (MoM 2.5D) – modeling of planar antennas (e.g., patch arrays) § XFDTD (FDTD) – broadband modeling of 3-D structures (e.g., spiral) § HFSS (FEM) – modeling of 3-D structures (e.g.,
  • The Development of HF Broadcast Antennas

    The Development of HF Broadcast Antennas

    Development of HF Broadcast Antennas FEATURES FEATURES Development of HF Broadcast Antennas the 50% power loss, but made the Rhombic fre - Free Europe and Radio Liberty sites. quency-sensitive, consequently losing the wide- Rhombic antennas are no longer recommend - The Development of HF bandwidth feature. The available bandwidth ed for HF broadcasting as the main lobe is nar - depends on the length of the wire and, using dif - row in both horizontal and vertical planes which ferent lengths of transmission line, it is possible to can result in the required service area not being Broadcast Antennas access two or three different broadcast bands. reliably covered because of the variations in the A typical rhombic antenna design uses side ionosphere. There are also a large number of lengths of several wavelengths and is at a height side lobes of a size sufficient to cause interfer - Former BBC Senior Transmitter Engineer Dave Porter G4OYX continues the story of the of between 0.5-1.0 λ at the middle of the operat - ence to other broadcasters, and a significant pro - development of HF broadcast antennas from curtain arrays to Allis antennas ing frequency range. portion of the transmitter power is dissipated in the terminating resistance. THE CORNER QUADRANT ANTENNA Post War it was found that if the Rhombic Antenna was stripped down and, instead of the four elements, had just two end-fed half-wave dipoles placed at a right angle to each other (as shown in Fig. 1) the result was a simple cost- effective antenna which had properties similar to the re-entrant Rhombic but with a much smaller footprint.