2014 First International Conference on Systems Informatics, Modelling and Simulation

Design and Analysis of Integrated RF Front-end Transceiver System Using Printed Circuit Technology for 5 GHz Wireless Communication Applications

Yasser M. Madany Nour Eldin H. Ismail Hayman A. Hassan Senior, Member IEEE, Comm. and Communications and Electronics Communications and Electronics Electro. Dep., Alexandria University, Department, Alexandria University, Department, Alexandria University, Alexandria, Egypt. Alexandria, Egypt. Alexandria, Egypt. [email protected] [email protected]

Abstract—The wireless market is developing very fast today today it is no longer reasonable that customers should have with a steadily increasing number of users all around the one handset for each standard. From a customer’s world. An increasing number of users and the constant need perspective one handset capable of switching between all for higher and higher data rates have led to an increasing standards is the optimal solution. The simplest, and most number of emerging wireless communication standards. As a straight forward, solution would of course be to include one result there is a huge demand for flexible and low-cost chip-set for each standard into for example a mobile phone architectures for portable applications. Modern radio trans- or a laptop. This would however also lead to a highly ceivers have to support several different standards. Moving increased cost and a very bulky terminal with short standby towards multi-standard radio, a high level of integration time due to high power consumption. The smallest, cheapest, becomes a necessity and only can be accomplished by new and most elegant solution would be to use a RF front-end improved radio architectures and full utilization of technology scaling. A (RF) front-end system has been capable of covering all possible standards, i.e., a software- designed, integrated and fabricated using printed circuit board defined radio. In this paper, RF front-end system has been (PCB). The system consists of single-pole double-throw (SPDT) introduced. The proposed structure has been designed using   transmitter/receiver (T/R) switch with PIN diode, a low noise duroid substrate with ( r = 6.15, tan = 0.0019) and (LNA), a power amplifier (PA) and other thickness of 0.635 mm. The characteristics of the proposed components. The components and sub-circuits based upon the structure are obtained and analyzed using HFSS simulator transmission line theory have been utilized for the system [2] to demonstrate the performance. The compact integrated design. All the sub-circuits and the entire system have been RF front-end system around 5 GHz, as a main frequency, has evaluated using a commercial software. The full design has been fabricated and measured. been fabricated and measured using network analyzer. It is shown that RF front-end system can be integrated in a PCB II. RF FRONT-END SYSTEM DESIGN STRUCTURE utilizing a conventional PCB process. This system integration A lot of effort has been made to seek an alternative or technique provides not only low cost but also high performance modified architecture to the conventional one such that the because of the elimination of parasitic associated with lumped requirements of the image-rejection and IF filters can be components in a conventional design. relaxed. The ultimate goal is to completely eliminate these Keywords- RF front-end; SPDT; LNA; PA; integrated off-chip filters. Several receiver architectures have been transceiver system; wireless communication applications. conceived to implement the idea. The low-IF and direct- conversion (or zero IF) are two of the most well-known. Direct-conversion is believed to be the most simple and I. INTRODUCTION straightforward way to build a [3]-[8]. By Wireless communication is today a very large and converting the RF signal directly to the base band, the image important market affecting our lives in many ways. The frequency no longer exists. number of wireless standards is increasing for every year and higher data rates are requested by even more users than A. SPDT-T/R Switch before. To make this possible a numerous number of The proposed identical SPDT-T/R switch with PIN diode different standards and technologies are used. A few structure is shown in Fig. 1. In a typical transceiver system, examples are GSM, WCDMA, Bluetooth, and WLAN primary aims are to direct high power RF signal from TX to (802.11a, b, g . . ) [1]. The FCC’s allocation of 300 MHz of ANT while preventing leakage of that large signal into more bandwidth in the 5 GHz frequency band (5.15–5.35/5.725– sensitive front-end of RX, as shown in Fig. 2. From Fig. 2, it 5.825 GHz) for the unlicensed national information was found that, in transmit mode (RF signals go through TX infrastructure (UNII), high data rate (up to 50 Mb/s) wireless to ANT), the PIN diodes are turned 'OFF'. Then, TX local area networks (WLAN) have become increasingly coupled-resonator becomes all-pass response while in the popular and important for mobile computing devices such as receive arm, the PIN diodes are turned 'ON'. Then, the RX notebook computers. The European counterpart is the coupled-resonator becomes band-stop response. Hence, the HIPERLAN (High Performance Radio LAN) system, which additional isolation can be obtained and also the receive arm also operates in the 5-GHz band (5.15–5.35/5.47–5.725 becomes absorptive port. The same operation can be GHz). With the increased number of wireless standards used obtained in the receive mode (RF signals go through ANT to

978-0-7695-5198-2/14 $31.00 © 2014 IEEE 190 DOI 10.1109/SIMS.2014.43 RX) when PIN diodes are turned 'ON' in the transmit arm; leading in phase by 90°. The port located on the same side as and PIN diodes are turned 'OFF' in the receive arm [9], [13]. the input port is isolated since there is no power reaching it, as shown in Fig. 4. The hybrid coupler can act as a phase /4 shifter to provide the necessary 90° characteristics to operate with I/Q signal for direct conversions [14].

PIN Diode /8 

5

/4 /2 /4

(a) TX-Side. (b) RX-Side. Figure 1. The proposed SPDT switch structure with PIN diode.

ANT OFF OFF ON ON

TX RX S12 S13 OFF ON S11

Transmitted RF Signal Leakage RF Signal S14

Figure 2. The proposed SPDT switch in transceiver system. Numerical simulation is used to obtain the S-parameter characteristics of the TX and RX sides of identical SPDT- T/R switch structures, as shown in Fig.3. g ANSOFT Figure 4. The hybrid coupler structure and S-parameters result. 0.00 -5.00 C. Wilkinson Power Divider -10.00 -15.00 S11 The Wilkinson power divider is such a network, with the -20.00 -25.00 useful property of being lossless when the output ports are -30.00 matched; that is, only reflected power is dissipated [14]. It -35.00 S-Parameters [dB] -40.00 can be made with arbitrary power division with equally split S21 TX-Side -45.00 3dB each port, as shown in Fig. 5. -50.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 Freq [GHz] 0.00 -5.00 -10.00 -15.00 S11 -20.00 -25.00 -30.00 -35.00 S-Parameters [dB] -40.00 S21 RX-Side -45.00 -50.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 Freq [GHz] Figure 3. The proposed SPDT-T/R sides simulation results.

Fig. 3 shows simulated S-parameter data of the two sides of SPDT switch networks. The basic behavior of the SPDT S11 switch shows RF properties in terms of low transmission  losses (S21 -1 dB, ON state) and high isolation (S21, OFF state) over a relatively wide frequency range. The reconfig- S13 urable using PIN diode is designed to satisfy that the SPDT S12 switch can be switched between ‘ON’ and ‘OFF’ states. B. SPDT-T/R Switch Figure 5. The Wilkinson power divider structure and S-parameters result. Quadrature hybrids or hybrid couplers are well known D. Low Noise Amplifier with Matching and RF Choke devices used for their ability to generate signals 90° out of The function of low noise amplifier (LNA) is to amplify phase at its outputs. The port closer to the input port is the incoming RF signal that arrives with low power before

191 the consecutive stages add more noise, provided that the S11 LNA adds very little noise itself. It should be placed as close to the as possible in order to have the highest signal possible. The LNA chip used is from Avago (MGA-665P8). Fig. 6 shows the LNA together with the distributed input S12 and output matching networks and RF choke. Also, the S- parameters simulation result has been obtained. RF choke is composed of a radial stub for RF- High Isolation Up to -85 dB transmission line to transfer RF-short at the radial stub to

RF-open at the LNA output. Figure 7. The double stage PA with matching networks and RF chock LNA Chip Location structures and S-parameters result.

F. RF Front-end Transceiver System The proposed system consists of SPDT-T/R switch with PIN diode, a LNA, a double stage PA and other microwave components, such as hybrid coupler, power divider, transmission line and matching networks to adapt the system with desired frequency, as shown in Fig. 8. The mechanical parameters in millimeter have been shown in Fig. 8 while the rest parameters remain as mentioned before.

Antenna

Input Output Port 2 LNA with Matching Networks RF Chock

S11

S12 Rx Signal High Isolation Up to -75 dB Tx Signal from LNA from PA

Figure 6. The LNA with matching networks and RF chock structures and S-parameters result

E. Power Amplifier with Matching and RF Choke Input Input Carrier Carrier Signal to Detected The power amplifier (PA) provides the necessary gain, Signal to PA Hybrid Signal Port 1 Matched minimum RF loss and undesired interaction among the RF Load Port 3 signals in order to fulfill this requirement. It is the most Transmitting Section Receiving Section critical active component in transmission. The PA chip used is from Avago (MGA-83563). Fig. 7 shows the double stage Input Carrier Signal PA together with the distributed input and output matching Figure 8. The proposed RF front-end transceiver system design structure. networks and RF choke. The S-parameters simulation result Fig. 8 shows the signal flow graph to analyze the S- has been obtained. parameters characteristics of the proposed design structure,

PA Chip Location as shown in Fig. 9.

S11 S13

S12

Double stage PA Input Output

Single stage PA PA with Matching RF Chock (a) S-parameters in dB.

192

-6 dB

-10 dB

(b) Surface current density, Jsur. Figure 9. The proposed RF front-end transceiver system simulation results. (b) With LNA and PA chips. III. THE INTEGRATED RF FRONT-END TRANSCEIVER Figure 11. The measured S-parameters in dB of the proposed fabricated proposed RF front-end transceiver system. SYSTEM EXPERIMENTAL MEASUREMENTS From measured S-parameters, f= 50.15 GHz, at antenna Photograph of the proposed fabricated miniaturized laboratory, as shown in Fig. 11(a), it was found that the input integrated RF Front-end Transceiver System structure at port (port 1), antenna (port 2) and detected signal (port 3) antenna laboratory is shown in Fig. 10. The measured S- have analyzed. Hence, from reference [14], for transmitting parameters in dB of the proposed structure can be analyzed side, the input port return loss (RL), S = -24 dB and the S- with network analyzer HP8719ES, as shown in Fig. 11. 11 parameter between port 1 and port 2, S = -58 dB, 21 S11[dB] = 20 log (r), then r = 0.063 2 Power transmitted = [1-(r) ]100 = 99.6% S [dB] = 20 log (r), then r = 0.00126 21 The gain = [1-(r)2]100 = 99.999%

and for receiving side, the return loss (RL), S22= -17.6 dB and the between port 2 and port 3, S32= -37 dB,

(a) Without LNA and PA chips. S22[dB] = 20 log (r), then r = 0.132 Power received = [1-(r)2]100 = 98.3%

S32[dB] = 20 log (r), then r = 0.0141 LNA The gain = [1-(r)2]100 = 99.999%

From Fig. 11(b), a narrow view at the frequency band

PA 4.8-5.2 GHz with LNA and PA chip has been illustrated. It PA was found that the measured S11 for Tx mode result has been differed slightly than the measured S11 for Rx mode result because of the effect of practical design accuracy according (b) With LNA and PA chips. to the design structure complexity, connectors and element Figure 10. The proposed fabricated proposed RF front-end transceiver chips (LNA and PA) welding. But, the measured Tx mode system at antenna Laboratory. and Rx mode results have been shared the frequency band for S11 -10dB.

IV. CONCLUSIONS

The revolutionary advances in integrated circuits (ICs) have brought the world of wireless communications into a completely new era. System-on-chip (SOC) is no longer a dream. New technologies acting as a driving force have pushed the personal wireless communications market into today’s boom. The market motivates low-cost, low-power and high performance circuit designs. To meet these requirements, communication system considerations and transceiver architecture innovations play a most essential role. In this paper, the design and analysis of fully integrated (a) Without LNA and PA chips.

193 RF front-end transceiver system is described using printed [12] S.Y.M.J.Hamzah, B.H.Ahmad, and P.W.Wong,"Multiband matched circuit technology. The proposed system architecture and bandstop filter," Proceedings of 2010 IEEE Asia-Pacific Conference on Applied Electromagnetics (APACE 2010), pp.1-4, November circuit design issues are discussed and a prototype is built 2010. and fabricated. The measured results have a good agreement [13] M.K.Zahari, B.H.Ahmad, N.A.Shairi, and P.W.Wong; with simulated results to introduce an integrated and ,"Reconfigurable matched bandstop filter," RF and Microwave miniaturized RF front-end transceiver system (6.9cm×4.3cm) Conference (RFM), 2011 IEEE International, pp.230-233, December at 5 GHz with SPDT-T/R switch, double stage PA and LNA. 2011. The proposed system has achieved excellent performance [14] D.M. Pozar, “Microwave engineering”, JohnWiley & Sons, Inc, 4th due to the elimination of parasitic associated with lumped edition, 2012. components in a conventional design with 99.6% power transmitted, 98.3% power received and 99.999% gain in both transmission and receiving sides to meet the requirements of 5 GHz wireless communication applications, such as the unlicensed 5 GHz band (802.11a/n). The presented work shows the possibilities of designing flexible RF front-ends for wireless transceivers using RF-sampling technique and printed circuit technology.

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