Design of low phase noise K‐band VCO using high quality factor resonator in 0.18 μm CMOS technology

Abstract

A novel resonator to improve the phase noise of a Voltage-Controlled Oscillator (VCO) utilizing double series resonances or two attenuation zeros to improve the susceptance slope parameter of the resonator circuit is proposed, and its effectiveness is demonstrated by designing a low phase noise K-band VCO. The first series resonance is created by an additional inductor (L) in series to the capacitor (C) in the parallel branch of a conventional LC-tank circuit, and the second one is realized by an additional capacitor in series to the whole resonator circuit. The additional L is realized by defected ground structures (DGS) so that there is no additional burden in the chip size. The proposed resonator is fabricated in 0.18 μm CMOS technology and has active quality factor of 101 and a compact size of 0.009 mm2 (0.00046 λ2). The measured return loss |S11| and insertion loss |S21| of the fabricated prototype resonator are 2.8 and 11 dB, respectively, at a center frequency of 37 GHz with 8 GHz of bandwidth. The resulting active quality (QK-) factor of the proposed resonator is enhanced significantly that, in returns, improves the phase noise. The design is implemented in 0.18 μm CMOS technology, and the post-layout simulation shows that VCO has a tuning range of 3.8% and phase noise of −114.4 dBc/Hz @1 MHz offset at 19.5 GHz oscillation. The VCO consumes 2.96 mW power resulting in a Figure of Merit (FoM) of −195.5 dB. The proposed resonators improve the VCO FoM by more than 5.5 dB compared to conventional LC resonator.