Wideband signal generator for cognitive radio five-port receiver

This paper presents an wideband ring VCO for cognitive radio five-port based receivers. A three-stage differential topology using transmission gates was adopted in order to maintain wide and linear tuning range and a good phase-noise. Monte-carlo analysis were made for evaluating the phase-shift response, which should be 120° between stages. Those analysis will be used to develop a behavioral model of the VCO with focus on five-port receiver simulations allowing time-saving. It was observed a fairly linear correlation between control voltage and oscillation frequency in the range between 200 MHz and 1800 MHz. The VCO was designed for IBM 130nm CMOS technology.