<正>A differential power amplifier(PA),designed using the linear-phase filter model,for a BPSK modulated ultra-wideband(UWB) system operating in the 3-5 GHz frequency range is presented.The proposed PA was fabricated using 0.18μm SMIC CMOS technology.To achieve sufficient linearity and efficiency,this PA operates in the class-AB region,delivering an output power of 8.5 dBm at an input-1 dB compression point of -0.5 dBm.It consumes 28.8 mW, realizing a flat gain of 9.11±0.39 dB and a very low group delay ripple of±8 ps across the whole band of operation.