Application of CPW based spiral-shaped defected ground structure to the reduction of phase noise in V-band MMIC oscillator

A CPW based spiral-shaped defected ground structure (DGS) is used in a MMIC for the first time to reduce the phase noise in a V-band MMIC oscillator. The parallel equivalent L-C components, resulting from defects on both ground planes in the CPW, produce a band rejection property. Hence the spiral-shaped DGS can be employed at the gate circuit of the series feedback oscillator to improve the quality factor of the oscillator. A V-band CPW MMIC oscillator, incorporated with this DGS resonator, was designed, fabricated and measured. To demonstrate the effect of the spiral-shaped DGS on phase noise, another oscillator with only a conventional open stub CPW line was also tested. The phase noise performance of the oscillator with the spiral-shaped DGS is improved by 8 dB compared to that of the oscillator without the DGS.