Active Inductor-Based Oscillator: A Promising Candidate for Low-Cost Low-Power Multi-Standard Signal Generation

This paper presents design techniques to enhance the tuning range and improve the phase noise performance of tunable active-inductor (TAI) oscillators. Noise analysis of the TAI suggests a direct trade-off between the range of tunable inductance and the output noise. Reducing the effective feedback resistance reduces the phase noise of the VCO, but simultaneously reduces the inductive tuning range. The decrease in tuning range can be compensated by increasing the capacitance at the second port of the gyrator-based active inductor. Measurements of the TAI-based VCOs in Si-CMOS technology demonstrate a phase noise improvement of around 15 dBc/Hz. The improved TAI-based VCO achieves a tuning range of 1.3 - 3.8 GHz and phase noise as low as -94 dBc/Hz at 1 MHz offset while consuming around 5 mW from a 1.8 V supply