A V-Band CMOS VCO With Digitally-Controlled Inductor for Frequency Tuning

This paper presents a digitally-controlled inductor (DCI) technique to tune the frequency of millimeter-wave (MMW) VCOs. The design guideline, which is to structure a larger coupled inductor when obtaining a required inductance, is derived to optimize the quality factor. To extend the tuning range and minimize the Q degradation, a DCI composed of a primary coil and two switched secondary coils is designed and proposed. Switching the two secondary coils on and off, individually, effective inductance seen from the primary coil for LC oscillation is varied. Implemented in a 65nm CMOS process, the MMW VCO prototype employing the DCI measures a 14% frequency tuning range from 49.2 to 56.6 GHz, phase noise from -87 to -93 dBc/Hz at 1-MHz offset, and the state-of-the-art FOM_A of -196.3 dBc/Hz, while consuming DC power of 7.2 mW and occupying small core area of only 0.02 mm².