Design of Coplanar Waveguide On-Chip Impedance-Matching Circuit for Wireless Receiver Front-End H. Kanaya, R. K. Pokharel, F. Koga, Z. Arima, S. Kim, and K. Yoshida Department of Electronics, Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka 812-8581, Japan Abstract — Recently, spiral inductors have widely been used instead of resistors in the design of matching circuits to enhance the thermal noise performance of a wireless transceiver. However, such elements usually have low quality factor (Q) and may encounter the self-resonance in microwave-frequency band which permits its use in higher frequencies, and on the other hand, they occupy the large on- chip space. This paper presents a new design theory for the impedance-matching circuits for a single-chip SiGe BiCMOS receiver front-end for 2.4 GHz-band wireless LAN (IEEE 802.11b). The presented matching circuits are composed of conductor-backed coplanar waveguide (CPW) meanderline resonators and impedance (K) inverter. The prototype front- end receiver is fabricated and measured. A few of the measured results to verify the design theory are presented. Index Terms — CPW line, impedance-matching circuit, receiver front-end, transmission-line theory. I. INTRODUCTION In the RF section of LSI chip, impedance-matching circuits are necessary for interconnecting each part such as low-noise amplifier (LNA), power amplifier (PA), duplexer, mixers, and so on, and lumped elements are usually used for the design of matching circuits. Among the lumped elements, spiral inductors are preferred in stead of resistors to enhance the thermal noise performance [1],[2]. However, they cannot be used at high frequency range because of the self-resonance and stray impedances. On the other hand, they also occupy large on- chip space. Distributed elements made of transmission lines are particularly effective when their size becomes smaller, as the operating frequency increases. Distributed elements using transmission lines have already been implemented in GaAs based monolithic microwave integrated circuit (MMIC). However, it is necessary to fabricate the on-chip matching circuit based on distributed element, in order to operate the RF-CMOS or RF-BiCOMS LSI in the high frequency region. Among various transmission lines, coplanar waveguide (CPW) line is easy to fabricate on the LSI chip because the signal line and ground plane exist on the same plane. In our previous studies [3],[4], some of the present authors proposed a design method of the CPW super-conducting impedance-matching circuit for interconnecting an antenna and duplexer. In this paper, the design theory of the CPW impedance- matching circuits for single-chip SiGe BiCMOS LNA and down-conversion mixer (DCM) for wireless LAN (@2.4 GHz-band) is presented using a commercial electromagnetic (EM) and SPICE co-simulator (ADS2004A; Agilent Technologies), and verified by comparing the simulation with the results measured on a fabricated chip. II. DESIGN OF LNA AND DCM WITH ON-CHIP IMPEDANCE- MATCHING CIRCUIT Fig. 1 shows the block diagram of single-chip direct conversion transceiver which is composed of diode switch, LNA, PA, down-conversion mixer (DCM), and up- conversion mixer (UCM). In the figure, the LNA and PA are with input and output matching circuits. The design value of the input impedance and output impedance are 50Ω for general purpose. Fig. 2 shows the schematics of the designed LNA and DCM. The DCM employs the double-balanced topology. The designed value of the Max gain of the LNA and noise figure (NF) is 17 dB and less than 3dB (@2.45 GHz) respectively. Similarly, the target conversion gain, NF, IF of the design mixer are 12 dB, less than 5 dB, and 15 MHz respectively. Each V CC and V DD of this process is 3.3V. Fig. 1. Block diagram of single chip direct-conversion transceiver. Present work Matching & Filter Circuit LNA PA SW ANT 1-Chip 50Ω UCM DCM 0 180 VCO Present work Matching & Filter Circuit LNA PA SW ANT 1-Chip 50Ω UCM DCM 0 180 0 180 VCO