This paper presents a voltage-controlled oscillator (VCO) realized in a 22 nm FDSOI CMOS technology for frequency-modulated continuous-wave (FMCW) radars. Several different circuit techniques applied to reduce phase noise, increase the tuning range and output power are described and validated with experimental results. Furthermore, carefully designed, reversed varactors are implemented to achieve a constant tuning slope, thus minimum FMCW-chirp error. The tuning range is 12.1 %, from 37.2 to 42 GHz, whith a tuning slope error of < 17 % and < 1 % for a 0.6 GHz automotive radar chirp. Meanwhile a phase noise of -93.4 dBc/Hz at 1 MHz offset is measured at 42 GHz. With 45.3 mW DC power consumption, 2.5 dBm output power are measured on a differential load, yielding a DC-to-RF efficiency of 3.6 %. With 0.015 mm2 the VCO is very compact. It performs remarkably well in every parameter when compared to the state of the art, especially the area, phase noise, dc-to-RF efficiency and provides a very linear control slope.