A novel defected ground structure and its application to a microwave oscillator

This paper presents a new defected ground structure (DGS) and its application to a microwave oscillator. The presented oscillator is designed so as to use the suggested defected ground structure as a feedback loop inducing a negative resistance as well as a frequency-selective circuit. Applying the feedback loop between the drain and the gate of a FET device produces a high gain and precise phase conversion in the feedback loop. The equivalent circuit parameters of the DGS are extracted by using a three-dimensional EM calculations and simple circuit analysis method. The implemented 9 GHz oscillator provides +8.5 dBm output with high power efficiency over 40%.