A single-LC-tank 5–10 GHz quadrature local oscillator for cognitive radio applications

Abstract

This paper presents a local oscillator (LO) that converts oscillation frequencies of 13.3–20GHz from a single-LC-tank VCO to the intended 5–10GHz with continuous frequency coverage. A 4-stage differential injection-locked ring oscillator (ILRO) is used after the latch-based divider to produce quadrature output phases without requiring 50% duty cycle of input signals as those of conventional divide-by-2 approaches. When implemented in 65nm CMOS, the prototype LO consumes 22mA at 1V supply and is able to exhibit a worst-case phase noise of −102dBc/Hz at 1MHz offset across the entire 5–10GHz band for projected cognitive radio applications.