X-band voltage-controlled oscillator with built-in envelope detection

ABSTRACT A wide‐tuning‐range X‐band voltage‐control oscillator (VCO) with built‐in envelope detectors is designed and measured. The VCO is implemented using a 0.18‐μm CMOS technology. The VCO core is composed of a cross‐coupled pair and a parallel‐LC resonator. The variable capacitance is implemented using MOS varactors. Large varactor capacitance and small transistor size are used to reduce the tuning‐range degradation due to the parasitic capacitance of the cross‐coupled pair and buffer amplifier. Each single‐ended output of the differential buffer amplifier is connected to a Greinacher voltage doubler, which serves as an envelope detector that senses the output power of the VCO and translates it into a dc voltage. The chip area of the VCO is 1.25 × 0.6 mm2. The measured frequency tuning range and FoMT (at 1‐MHz offset) are 31.7% and −192.5 dBc/Hz, respectively. The relation between the VCO output power and detector output voltage is characterized. Using the relation, the envelope detectors can be used for real‐time monitoring of the power level at any location in a chip, providing built‐in self‐test capability. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:11–14, 2014