A capacitively-coupled 5GHz CMOS LC oscillator with bias tuning capability

A novel bias and tuning scheme for capacitively cross-coupled inductance-capacitance (LC) oscillators is presented. This scheme allows more flexibility in defining the operating point of the cross-coupled transistors, together with wide frequency tunability. A capacitively coupled LC oscillator at 5 GHz has been designed in CMOS UMC 0.18 mum technology. The bias network is realized with an all-transistor voltage reference. The oscillator is tunable in the 5 GHz-9 GHz frequency range. Phase noise performance is maintained over the entire frequency range, with -58 dBc/Hz at 100 kHz offset and -116 dBc/Hz at 1 MHz.