K-band CMOS VCO using a wide tuning range varactor

Abstract

This article presents a K-band CMOS voltage controlled oscillator (VCO) using a wide tuning range MOSFET varactor. The proposed varactor consists of a MOSFET in which the source and drain are connected to each other through a large resistor, the body is grounded through another large resistor, and the gate and source are connected through a capacitor. The newly proposed varactor improves the tuning range of the capacitance compared to that in a conventional MOSFET varactor and a resistors-added varactor because two large resistors partially cancels the parasitic capacitances of the MOSFET in the depletion mode, and the external capacitor supplements additional capacitance in the inversion mode. The proposed varactor achieves a capacitance tuning range of +/- 64.5%. The voltage controlled oscillator using the proposed varactor features a wide tuning range characteristic of 11.7% in the K-Band and shows a good figure-of-merit of -186.5 dBc/Hz.