Design of a Wideband Microstrip Bidirectional Absorptive Bandstop Filter

A planar bidirectional absorptive bandstop filter with a wide absorptive bandwidth and compact circuit size is proposed. The proposed absorptive bandstop filter is developed from the absorptive coupled line. Moreover, by adopting the symmetrical structure, both the input and output ports can be used to absorb the injected power. Furthermore, to broaden the stopband bandwidth, the π-shaped transmission lines are included. In addition, design equations are provided for synthesizing the proposed absorptive bandstop filter. In order to validate the analysis, a wide-absorptive bandstop filter has been fabricated, with 20 dB for the absorption and 18.7% for the fractional bandwidth.