A 5.3 GHz phase shift tuned I/Q LC oscillator with 1.1 GHz tuning range

In this paper phase shift tuning of a 5.3 GHz quadrature LC oscillator is investigated. By varying the phase shift of the circuits that couple two LC oscillator stages, a 1.1 GHz tuning range is achieved. Dependency of tuning range and phase noise on the quality factor of the LC resonators is explored on the behavioral level. Expressions are given for the tuning range and an effective quality factor, as a function of the resonator quality, its phase shift and its resonance frequency. The oscillator is realized in a mainstream 30 GHz f_T BiCMOS process and dissipates 45 mW (nominal) with 2.7 V supply voltage. The dependency of the tuning range on the resonator quality is measured by varying the quality factor of a varactor incorporated in the LC resonators of the I/Q oscillator. Measured L(2 MHz) is -108 dBc/Hz at 5.6 GHz.