A symmetrical 6-GHz fully integrated cascode coupling CMOS LC quadrature VCO

Abstract

A fully symmetrical integrated quadrature LC oscillator with a wide tuning range of 1.2 GHz is presented. The quadrature voltage-controlled oscillator (QVCO) is implemented using a symmetrical coupling method which has been used to produce the large tuning range with a low control voltage and to achieve good phase noise performance in 0.18 mu m complementary metal oxide semiconductor technology. The measured phase noise at 1 MHz offset from the center frequency (5.5 GHz) is -115 dBc/Hz. The QVCO draws 3.2 mA from a 1.8 V supply. The equivalent phase error between I and Q signal was at most 0.5 degrees.