A low-phase-noise K-band CMOS VCO

A novel circuit topology for low-phase-noise voltage controlled oscillators (VCOs) is presented in this letter. By employing a PMOS cross-coupled pair with a capacitive feedback, superior circuit performance can be achieved especially at higher frequencies. Based on the proposed architecture, a prototype VCO implemented in a 0.18-mu m CMOS process is demonstrated for K-band applications. From the measurement results, the VCO exhibits a 510-MHz frequency tuning range at 20 GHz. The output power and the phase noise at 1-MHz offset are -3 dBm and -111 dBc/Hz, respectively. The fabricated circuit consumes a dc power of 32 mW from a 1.8-V supply voltage.