Design and Analysis of a Low Phase Noise Low Power Ring-VCO

Abstract

A low phase noise low power ring voltage-controlled oscillator (Ring-VCO) is proposed for phase-locked loops (PLLs) in the 802.11ah communication protocol band. A three-stage Ring-VCO with dual-path structure delay cells is designed to meet the high performance requirements of Internet of Things. The main noise source in the differential delay cell can be eliminated at the differential output, thus reducing phase noise. Implemented in an old TSMC 0.18 µm CMOS process, the Ring-VCO achieves a tuning range of 343.56-974.56 MHz. The phase noise at 1 MHz offset varies from -116.28 to -108.74 dBc/Hz, and the current consumed is 2.27 mA.