A Two-Stage $S-/X$ -Band CMOS Power Amplifier for High-Resolution Radar Transceivers

This paper presents a reconfigurable S-/X-band power amplifier (PA) integrated into a 0.18-μm RF CMOS process. A switchable transformer for output matching is operated by tuning its primary winding and a shunt capacitor under a 50-Ω load with passive efficiency of more than 63%/67% for the S-/X-band. Series resonant circuits with bond wires are employed at common-mode nodes, greatly improving the X-band performance of the PA. Despite the use of interstage matching without any tunable elements, the PA presents a power gain of more than 19.5 dB at both 3 and 8 GHz. The PA provides saturated output power of 24.8/21.5 (21.5) dBm with a power-added efficiency of 32.8%/11.1% (10.7%) at 3/8 (9) GHz. The 1-dB bandwidth is 0.6/2 GHz (2.8-3.4/7.5-9.5 GHz) for the S-/X-band. This amplifier demonstrates suitable performance for dual-band high-resolution radar transceivers.