An Ultra-Low-Power Octave-Tuning VCO IC With a Single Analog Voltage-Controlled Novel Varactor

In this paper, an ultra-low-power octave-tuning voltage-controlled oscillator (VCO) integrated circuit (IC) is proposed, using a novel varactor with a single control voltage. The novel varactor including VCO-gain ( ${K}_{\mathrm{ VCO}}$ ) improving structure consists of two parallel-connected inversion-mode MOS (I-MOS) -based varactors with shifted bias and an NMOSFET operating as a variable resistor. This novel varactor is able to give a large capacitance variation with a single analog control voltage. The proposed wideband VCO IC implementing this novel varactor is designed, fabricated, and evaluated fully on-wafer in 40-nm CMOS SOI technology. The proposed wideband VCO IC has exhibited a completely continuous measured tuning range (TR) of 67.9% from 3.2 to 6.49 GHz. The measured dc power consumption is from 0.35 to 1.36 mW throughout the whole TR under a supply voltage of 0.36 V. This is an extremely low dc power consumption among the reported sub-10-GHz octave-tuning VCO ICs so far. The measured peak figure-of-merit including TR (FoMT) of the proposed VCO IC is 210.4 dBc/Hz with a carrier frequency of 6.49 GHz.