A 4.1-to-4.5GHz FMCW radar transmitter suitable for long-distance detection using 180-nm CMOS process is introduced in this paper. The chirp signal generator is realized by an open-loop voltage-controlled oscillator (VCO) with a 3-bit switching capacitor array and a distributed-bias varactor array, which guarantee the high linearity of the frequency tuning curves. A 2-series stacking current mode class-D (CMCD) power amplifier (PA) is proposed to achieve remarkable power transmission and efficiency. The measured phase noise from the highest frequency is -123.0_dBc/Hz at 1MHz offset, and the tuning linearity can be calibrated to less than 10%. The output power is more than 22dBm and the drain efficiency is more than 30% across the whole 4.1-to-4.5GHz. The proposed FMCW transmitter occupies 3mm×2.3mm die area, including testing pads.