A Low Phase Noise X-Band Quadrature VCO by Using Transconductance Linearization Technique

This paper presents a quadrature voltage-controlled-oscillator (QVCO) based on transconductance linearization technique. In this design, the LC-Tank was decoupled form switching MOSFET by capacitors rather than direct connecting, and the large signal voltage cross MOSFET was decreased. This design is able to reduce the nonlinearity of MOSFET transconductance and suppress output phase noise as result. The proposed circuit draws 8.36mA from a 1.8V DC supply. The phase noise is -119dBc/Hz at 1MHz offset and the tuning range is 5% wide at a center frequency of 9.36 GHz. And the phase error between I and Q signals is at most 1.5 degree. The prototype was designed and simulated in GF 130nm CMOS process. According the simulating result of layout, this proposed QVCO attains a figure-of-merit (FoM) of 198.5dBC/Hz.