This article presents a new microwave oscillator incorporating a corrugated coplanar waveguide (CCPW) electromagnetic bandgap structure as its terminating resonance component. The fully. planar CCPW oscillator, oscillating at a frequency of 5.41 GHz, showed a phase noise reduction of 8 dB at 1 MHz offset and (an increased second harmonic suppression of 10.16 dB and results in DC-AC power efficiency enhancement of 7.2% when compared to those of a conventional CPW oscillator without the CCPW structure. (C) 2006 Wiley Perodicals. Inc.