This paper presents two ultra-low voltage and high performance VCO ICs with novel harmonic tuned LC tank which provides different harmonic impedance and shapes the pseudo-square drain voltage waveform of transistors. In the novel tank, two additional inductors are connected between the drains of the cross-coupled pMOSFETs and the conventional LC tank, and they effectively decrease second harmonic load impedance and increase third harmonic load impedance of the transistors. In this paper, the novel harmonic tuned LC tank is applied to two different structure VCOs. These two VCOs exhibit over 2 dB better phase noise performance than conventional LC tank VCOs among all tuning range. The conventional and proposed VCO ICs are designed, fabricated and measured on wafer in 45-nm SOI CMOS technology. With novel harmonic tuned LC tank, the novel two VCOs exhibit measured best phase-noise of −125.7 and −129.3 dBc/Hz at 10 MHz offset and related FoM of −190.2 and −190.5 dBc/Hz at a supply voltage of 0.3 V and 0.35 V, respectively. Frequency tuning range of the two VCOs are from 13.01 to 14.34 GHz and from 15.02 to 16.03GHz, respectively.
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