A Low Phase-Noise Wide Tuning-Range Quadrature Oscillator Using a Transformer-Based Dual-Resonance LC Ring

This paper presents a dual-band quadrature voltage-controlled oscillator (QVCO) using a transformer-based high-order LC-ring resonator, which inherently provides quadrature signals without requiring noisy coupling transistors as in traditional approaches, thereby achieving low phase-noise performance. Moreover, the proposed resonator shows two possible oscillation frequencies, which are exploited to realize a wide-tuning range QVCO employing a mode-switching transistor network. Due to the use of transformers, the oscillator has a minimal area penalty compared to the conventional designs. The implemented prototype in a 65-nm CMOS process achieves a continuous tuning range of 77.8% from 2.75 to 6.25 GHz while consuming from 9.7 to 15.6 mA current from a 0.6-V supply. The measured phase-noise figure-of-merit at 1-MHz offset ranges from 184 to 188.2 dB throughout the entire tuning range. The QVCO also exhibits good quadrature accuracy with 1.5° maximum phase error and occupies a relatively small silicon area of 0.35 mm².