K-Band Low Phase Noise Inductive Coupled VCO

A low phase noise inductive coupled voltage-controlled oscillator has been investigated and demonstrated in this paper. It is found in this work that to improve the phase noise of the inductive coupled VCO, high coupling coefficient and low parasitic resistance of inductors are essential, moreover, in the case of the parasitic resistance ratio between drain-side inductor and gate-side inductor, R-G/R-D, is low, the phase noise is improved. To confirm them, four transformers which have different coupling coefficient and different R-G/R-D ratio were designed and VCOs which adopted these four transformer were designed, fabricated, and measured. In the measurement result, difference of the phase noise was obtained due to difference of the coupling coefficient and the parasitic resistance ratio. The measurement results showed the VCO using inductor of M4 vs M6+M5+M3 exhibited the minimum phase noise since the inductor of M4 vs M6+M5+M3 has lower R-G/R-D and higher coupling coefficient. The measured phase noise of that VCO exhibited -103.3 dBc/Hz at 1 MHz offset from 23.5 GHz oscillation frequency with the power consumption of 19.8 mW. The process technology used in this work is TSMC-180 nm CMOS.