A compact bandpass filter with enhanced stopband characteristics by an asymmetric cross-shape defected ground structure

In this paper, we present an effective technique to enhance stopband bandwidth for a bandpass filter by using an asymmetric, cross-shape defected ground structure (CSDGS). A single CSDGS can provide a higher attenuation rate near passband and broader stopband bandwidth. Moreover, with the asymmetric CSDGS, two different resonant frequencies can be excited and controlled independently, resulting in synthesizing a passband. The synthesized bandpass filter can be modeled by parallel LC resonant circuits in connection with T-networks. The bandwidth and insertion loss of this bandpass filter at 4.2 GHz is 28.6% and -1.44 dB, respectively, and 20 dB rejection in the stopband is up to four times the central frequency. All the synthesized bandpass filters have been measured and are in good agreement with simulated results.

Photonic-band-gap resonator gyrotron

We report the design and experimental demonstration of a gyrotron oscillator using a photonic-band-gap (PBG) structure to eliminate mode competition in a highly overmoded resonator. The PBG cavity supports a TE(041)-like mode at 140 GHz and is designed to have no competing modes over a minimum frequency range delta omega/omega of 30% about the design mode. Experimental operation of a PBG gyrotron at 68 kV and 5 A produced 25 kW of peak power in the design mode. No other modes were observed over the full predicted operating range about the design mode. PBG cavities show great promise for applications in vacuum electron devices in the millimeter- and submillimeter-wave bands.