An Inverted Complementary Cross-Coupled VCO to Reduce Phase Noise Sensitivity to KVCO

This letter presents an inverted complementary cross-coupled voltage-controlled oscillator (VCO) to reduce its phase noise (PN) sensitivity to VCO gain (K-VCO) implemented in a standard 28-nm bulk CMOS technology. Unlike conventional complementary VCO, the proposed topology places the NMOS switching pairs on the top of the PMOS pairs to constitute the inverted complementary cross-coupled topology to minimize the low-frequency noise up-conversion by varactors when with a large K-VCO. This topology can achieve both low PN at far offset frequency and a desired large continuous frequency tuning range for high-resolution millimeter-wave radar simultaneously. For example, when K-VCO varies with control voltage from 40 to 509 MHz/V, the PN only changes 0.68 dB at 10-MHz offset. The fabricated prototype achieves a PN of -133.63 dBc/Hz at 10-MHz offset from 18.9 GHz, and the corresponding figure-of-merit (FoM) is -185.5 dBc/Hz. The measured frequency tuning range is 18.75-20.75 GHz (10.13%).