15.4-17 GHz-, 187.4 dBc/Hz FoM VCO With Current Reused Coupled Oscillator and Improved Noise Circulation

This paper presents a current-reused coupled oscillator with improved noise circulating technique for phase noise improvement. The proposed current-reused coupled oscillator with order of 2, where the noise circulation oscillator is stacked on top of PMOS cross-coupled oscillator solves the strict trade-off between power consumption and phase noise. The degeneration transistors for noise circulating operations are biased in triode-region instead of in saturation to provide an optimum delay in loop gain, such that the positive and negative phase change in the normalized impulse sensitivity function (ISF) become more symmetric. Thus, the 1/f3 phase noise is significantly improved. The voltage-controlled oscillator (VCO) was implemented using CMOS 65nm technology, and the measurement results demonstrated its operation within a frequency range of 15.4-17 GHz (9.8% tuning range). Despite its low power dissipation of 6.3 mW, the VCO design exhibits excellent performance, offering a phase noise of -111.2 dBc/Hz at 1 MHz offset frequency. Furthermore, the proposed VCO attains a figure of merit (FoM) of -187.4 dBc/Hz.