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

Yasser M. Madany Senior, Member IEEE, Comm. and

Electro. Dep., Alexandria University, Alexandria, Egypt. ymadany@ieee.org

Nour Eldin H. Ismail Communications and Electronics

Department, Alexandria University, Alexandria, Egypt.

Hayman A. Hassan Communications and Electronics

Department, Alexandria University, Alexandria, Egypt.

hayman.hassen@yahoo.com

Abstract—The wireless market is developing very fast today with a steadily increasing number of users all around the world. An increasing number of users and the constant need for higher and higher data rates have led to an increasing number of emerging wireless communication standards. As a result there is a huge demand for flexible and low-cost radio architectures for portable applications. Modern radio trans-ceivers have to support several different standards. Moving towards multi-standard radio, a high level of integration becomes a necessity and only can be accomplished by new improved radio architectures and full utilization of technology scaling. A radio frequency (RF) front-end system has been designed, integrated and fabricated using printed circuit board (PCB). The system consists of single-pole double-throw (SPDT) transmitter/receiver (T/R) switch with PIN diode, a low noise amplifier (LNA), a power amplifier (PA) and other microwave components. The components and sub-circuits based upon the transmission line theory have been utilized for the system design. All the sub-circuits and the entire system have been evaluated using a commercial software. The full design has been fabricated and measured using network analyzer. It is shown that RF front-end system can be integrated in a PCB utilizing a conventional PCB process. This system integration technique provides not only low cost but also high performance because of the elimination of parasitic associated with lumped components in a conventional design.

Keywords- RF front-end; SPDT; LNA; PA; integrated transceiver system; wireless communication applications.

I. INTRODUCTION Wireless communication is today a very large and

important market affecting our lives in many ways. The number of wireless standards is increasing for every year and higher data rates are requested by even more users than before. To make this possible a numerous number of different standards and technologies are used. A few examples are GSM, WCDMA, Bluetooth, and WLAN (802.11a, b, g . . ) [1]. The FCC’s allocation of 300 MHz of bandwidth in the 5 GHz frequency band (5.15–5.35/5.725–5.825 GHz) for the unlicensed national information infrastructure (UNII), high data rate (up to 50 Mb/s) wireless local area networks (WLAN) have become increasingly popular and important for mobile computing devices such as notebook computers. The European counterpart is the HIPERLAN (High Performance Radio LAN) system, which also operates in the 5-GHz band (5.15–5.35/5.47–5.725 GHz). With the increased number of wireless standards used

today it is no longer reasonable that customers should have one handset for each standard. From a customer’s perspective one handset capable of switching between all standards is the optimal solution. The simplest, and most straight forward, solution would of course be to include one chip-set for each standard into for example a mobile phone or a laptop. This would however also lead to a highly increased cost and a very bulky terminal with short standby time due to high power consumption. The smallest, cheapest, and most elegant solution would be to use a RF front-end capable of covering all possible standards, i.e., a software-defined radio. In this paper, RF front-end system has been introduced. The proposed structure has been designed using duroid substrate with (�r = 6.15, tan� = 0.0019) and thickness of 0.635 mm. The characteristics of the proposed structure are obtained and analyzed using HFSS simulator [2] to demonstrate the performance. The compact integrated RF front-end system around 5 GHz, as a main frequency, has been fabricated and measured.

II. RF FRONT-END SYSTEM DESIGN STRUCTURE A lot of effort has been made to seek an alternative or

modified architecture to the conventional one such that the requirements of the image-rejection and IF filters can be relaxed. The ultimate goal is to completely eliminate these off-chip filters. Several receiver architectures have been 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 straightforward way to build a radio receiver [3]-[8]. By converting the RF signal directly to the base band, the image frequency no longer exists.

A. SPDT-T/R Switch The proposed identical SPDT-T/R switch with PIN diode

structure is shown in Fig. 1. In a typical transceiver system, primary aims are to direct high power RF signal from TX to ANT while preventing leakage of that large signal into more sensitive front-end of RX, as shown in Fig. 2. From Fig. 2, it was found that, in transmit mode (RF signals go through TX to ANT), the PIN diodes are turned 'OFF'. Then, TX coupled-resonator becomes all-pass response while in the receive arm, the PIN diodes are turned 'ON'. Then, the RX coupled-resonator becomes band-stop response. Hence, the additional isolation can be obtained and also the receive arm becomes absorptive port. The same operation can be obtained in the receive mode (RF signals go through ANT to

2014 First International Conference on Systems Informatics, Modelling and Simulation

978-0-7695-5198-2/14 $31.00 © 2014 IEEE

DOI 10.1109/SIMS.2014.43

190

2014 First International Conference on Systems Informatics, Modelling and Simulation

978-0-7695-5198-2/14 $31.00 © 2014 IEEE

DOI 10.1109/SIMS.2014.43

190

2014 First International Conference on Systems Informatics, Modelling and Simulation

978-0-7695-5198-2/14 $31.00 © 2014 IEEE

DOI 10.1109/SIMS.2014.43

190

PIN Diode

�/4

�/2 �/4 �/4

5�/8

RX

ANT

TX

Transmitted RF Signal

ON OFF

OFF OFF ON ON

Leakage RF Signal

RX) when PIN diodes are turned 'ON' in the transmit arm; and PIN diodes are turned 'OFF' in the receive arm [9], [13].

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

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.

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 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-urable using PIN diode is designed to satisfy that the SPDT switch can be switched between ‘ON’ and ‘OFF’ states.

B. SPDT-T/R Switch Quadrature hybrids or hybrid couplers are well known

devices used for their ability to generate signals 90° out of phase at its outputs. The port closer to the input port is

leading in phase by 90°. The port located on the same side as 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 shifter to provide the necessary 90° characteristics to operate with I/Q signal for direct conversions [14].

Figure 4. The hybrid coupler structure and S-parameters result.

C. Wilkinson Power Divider The Wilkinson power divider is such a network, with the

useful property of being lossless when the output ports are matched; that is, only reflected power is dissipated [14]. It can be made with arbitrary power division with equally split 3dB each port, as shown in Fig. 5.

Figure 5. The Wilkinson power divider structure and S-parameters result.

D. Low Noise Amplifier with Matching and RF Choke The function of low noise amplifier (LNA) is to amplify

the incoming RF signal that arrives with low power before

1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00Freq [GHz]

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eter

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TX-Side

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LNA Chip Location

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LNA with Matching Networks RF Chock

Output

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Input

PA with Matching

Double stage PA

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PA Chip Location

the consecutive stages add more noise, provided that the LNA adds very little noise itself. It should be placed as close to the antenna 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 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-������ �� �� �� �transmission line to transfer RF-short at the radial stub to RF-open at the LNA output.

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

E. Power Amplifier with Matching and RF Choke The power amplifier (PA) provides the necessary gain,

minimum RF loss and undesired interaction among the RF signals in order to fulfill this requirement. It is the most critical active component in transmission. The PA chip used is from Avago (MGA-83563). Fig. 7 shows the double stage PA together with the distributed input and output matching networks and RF choke. The S-parameters simulation result has been obtained.

Figure 7. The double stage PA with matching networks and RF chock 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, antenna feed 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.

Figure 8. The proposed RF front-end transceiver system design structure.

Fig. 8 shows the signal flow graph to analyze the S-parameters characteristics of the proposed design structure, as shown in Fig. 9.

(a) S-parameters in dB.

S12

S11

High Isolation Up to -75 dB

S11

S12

High Isolation Up to -85 dB

Transmitting Section Receiving Section

Input Carrier Signal

Input Carrier Signal to Hybrid

Input Carrier

Signal to PA Detected

Signal Matched Load

Rx Signal from LNA Tx Signal

from PA

Antenna

Port 2

Port 3 Port 1

S12

S13 S11

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(b) Surface current density, Jsur. Figure 9. The proposed RF front-end transceiver system simulation

results.

III. THE INTEGRATED RF FRONT-END TRANSCEIVER SYSTEM EXPERIMENTAL MEASUREMENTS

Photograph of the proposed fabricated miniaturized integrated RF Front-end Transceiver System structure at antenna laboratory is shown in Fig. 10. The measured S-parameters in dB of the proposed structure can be analyzed with network analyzer HP8719ES, as shown in Fig. 11.

(a) Without LNA and PA chips.

(b) With LNA and PA chips. Figure 10. The proposed fabricated proposed RF front-end transceiver

system at antenna Laboratory.

(a) Without LNA and PA chips.

(b) With LNA and PA chips. Figure 11. The measured S-parameters in dB of the proposed fabricated

proposed RF front-end transceiver system.

From measured S-parameters, f= 5�0.15 GHz, at antenna laboratory, as shown in Fig. 11(a), it was found that the input port (port 1), antenna (port 2) and detected signal (port 3) have analyzed. Hence, from reference [14], for transmitting side, the input port return loss (RL), S11= -24 dB and the S-parameter between port 1 and port 2, S21= -58 dB,

S11[dB] = 20 log (r), then r = 0.063

Power transmitted = [1-(r)2]�100 = 99.6%

S21[dB] = 20 log (r), then r = 0.00126

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,

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

The gain = [1-(r)2]�100 = 99.999%

From Fig. 11(b), a narrow view at the frequency band 4.8-5.2 GHz with LNA and PA chip has been illustrated. It 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 to the design structure complexity, connectors and element chips (LNA and PA) welding. But, the measured Tx mode 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

LNA

PA PA

-6 dB -10 dB

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RF front-end transceiver system is described using printed circuit technology. The proposed system architecture and circuit design issues are discussed and a prototype is built and fabricated. The measured results have a good agreement with simulated results to introduce an integrated and miniaturized RF front-end transceiver system (6.9cm×4.3cm) at 5 GHz with SPDT-T/R switch, double stage PA and LNA. The proposed system has achieved excellent performance due to the elimination of parasitic associated with lumped 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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