A Ku-band wideband power amplifier (PA) for FMCW radar application is proposed and implemented in 65-nm bulk CMOS technology. The PA consists of 3 stages of class AB amplifiers to achieve high gain and high power efficiency. To obtain low group delay (GD), low amplitude ripple and wide bandwidth, transformer and inductor based matching network is designed to meet the requirements. Including pads, the PA occupies a compact chip area of 0.62 mm². Consuming 118 mA current from 1.2 V supply voltage, it demonstrates output saturation power of 13.04 dBm. The measured 3 dB bandwidth is 5.5 GHz with maximum gain 20.65 dB at 15.5 GHz. Finally, the PA is integrated with a (frequency modulated continuous wave) FMCW signal generator to constitute a FMCW radar transmitter.