Design of a K-Band VCO Implementing T-Type LC Network in 0.18-μm CMOS Technology

A symmetrical T-type
LC
network is presented to design a low-noise quasi-millimeter-wave voltage-controlled oscillator (VCO) for the first time. For the same value of inductance, the T-type
LC
network obtains an enhanced resonant frequency compared to the conventional parallel
LC
resonator. This characteristic relaxes the capacitance budget while designing quasi-millimeter wave VCO utilizing the proposed network. The network is realized by connecting a ground capacitor to a U-shape inductor. Finally, the symmetrical T-type
LC
network is implemented in a
$K$
-band VCO and prototyped in a 0.18-
$\mu \text{m}$
CMOS technology. The chip area is only 0.1 mm
²
. The proposed VCO achieves a frequency tuning range of 14.5%, from 21.8 to 25.2 GHz. The measurement result shows that the VCO has a phase noise of −112.9 dBc/Hz at a 1-MHz offset of 23.12-GHz oscillation frequency while consuming 4.1 mW. This results in a figure of merit (FoM) of the proposed VCO to be −194.9 dB.