This letter presents the improvement of the phase noise (PN) of a voltage-controlled oscillator (VCO) by using a defected ground structure (DGS) resonator with a high-band transmission pole. The proposed DGS resonator has two loops in a coplanar stripline topology. The outer loop is loaded by a series capacitance, which produces the high-band transmission pole. The overall combination has a parallel capacitor to generate the necessary parallel resonance for the VCO operation. This proposed DGS resonator has a sharper impedance and frequency response slope, which results in an improved quality factor. In return, utilization of this DGS resonator into a KU-Band VCO reduces its PN. The prototyped VCO in 0.18-µm CMOS oscillates at 15.52 GHz and shows a PN of −111.27 and −134.07 dBc/Hz at 1- and 10-MHz offset, respectively, while consuming 3.3-mW power. The VCO has a frequency tuning range of 9.5%, which results in a figure of merit (FoM) of −192.7 dB.
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