An X-band SIW-DGS bandpass filter with improved stopband performance

In this paper, a substrate integrated waveguide (SIW)-to-defected ground structure (DGS) bandpass filter with moderate fractional bandwidth and improved stopband performance is proposed and demonstrated for X-band radar application. Design considerations including the design approach are addressed. A third-order filter with a passband of 8.8-10.1 GHz is fabricated on a single-layer Rogers RT/Duroid 5880 substrate using linear arrays of metallized via-holes by a standard printed circuit board process. Measured results of the filter agree very well with the simulated results, showing the in-band insertion loss is 1.3 dB or less, and in-band return loss is better than 20dB, respectively. The stopband rejection in the frequency band of 12-22 GHz is better than 35 dB.