Simple electromagnetic bandgap structure for the side band suppression of the ring ultra-wideband bandpass filter

Ultra-wideband (UWB) filters are of great interests for the applications in UWB communications due to the growing demand of high volume video and audio data transmission. There are many literatures available for the design of microwave ultra-wideband filters and the sideband suppression is one of the important concerns for the actual implementation. As the passband bandwidth becomes broader, the achievement of sideband suppression would become more difficult since the suppressing circuit must not distort the wide passband. In our previous publications, circuits such as the interdigital lines or high order low pass filters are utilized for the sideband suppression; however, the determination of the structure details somehow is complicated. In this literature, a simple tapered 1D electromagnetic bandgap structure is proposed for the sideband suppression of a ring ultra-wideband filter with ~8GHz passband ranging from 5GHz to 13GHz. As shown in Figure 1, the bandgap structure is composed by tapered 1D etched circular array serving as the ground plane to attain the sideband suppression. Based on the EM simulation, the sideband can be suppressed ~20dB; this result is comparable to our previous work but the design is much easier since only the size of the circular hole array has to be worked out.