A Class-C 3-phase CMOS Capacitive-Coupled VCO

Abstract

This letter presents a 3-phase class-C current reused voltage controlled oscillator (VCO). The prototype 5 GHz VCO in 0.18 μm CMOS process is implemented to generate signal with 3 output phases and it uses three identical single-ended current reused VCOs in a ring configuration. A dynamic bias circuit is used to reduce the power consumption, and the back-gate BJTs in PMOSFETs are used as a phase coupling device, the circuit oscillates from 4.48 GHz to 5.1 GHz and the power consumption is 3.53 mW at 1.0 V supply voltage. The measured phase noise is −116.52 dBc/Hz at 1 MHz offset frequency from 5.08 GHz. The VCO occupies a chip area of 1.0 × 0.72 mm2and provides a figure of merit of −185.16 dBc/Hz.