A quadrature relaxation oscillator-mixer in CMOS

Abstract

This paper describes the design of a quadrature cross-coupled oscillator circuit integrated which also realizes the mixer function in a phase lock loop (PLL). This should be able to provide a very accurate phase relation (<1/spl deg/). This combined oscillator/mixer is first evaluated using a high-level model, in up and downconverter configurations. A circuit implementation is then carried out, in which all the variables are kept independent at circuit level, ensuring a practical implementation close to that of the high-level model. The circuit is designed in a standard 0.35 /spl mu/m CMOS technology with an oscillation frequency of 900 MHz, it has an overall area of 521 /spl times/ 515 /spl mu/m/sup 2/ (157 /spl times/ 119 /spl mu/m/sup 2/ for the IQ oscillator/mixer circuit) and a power consumption of 70 mW with a 3 V power supply. The circuit performance is evaluated by simulation.