A Ku-Band 20.4% Tuning Range VCO With a Tunable Harmonic-Resonant Transformer in 55 nm CMOS

This letter presents a digital-process-based and wide-tuning-range voltage-controlled oscillator (VCO) with a tunable harmonic-resonant transformer. By adding fixed proportional common-mode (CM) and differential-mode (DM) capacitors banks, the first-to-second- and first-to-third-harmonic resonances are achieved across the entire frequency range lowering the average phase noise. A tunable transformer is also utilized to further widen the tuning range. The VCO is fabricated in a 55 nm complementary metal-oxide-semiconductor (CMOS) process without thick top metal, occupying an area of
$0.59~\mathrm {mm^{2}}$
. It achieves a tuning range of 2.94 GHz (20.4%) with a center frequency of 14.4 GHz. The measured phase noise at 1-MHz offset is −108.62 dBc/Hz. The power consumption of the oscillator core is 15 mW with a supply of 1.2 V, demonstrating a figure of merit (FOM) and FOM
$\mathrm {_{T}}$
of −180.10 and −186.22 dBc/Hz, respectively.