High-performance ultra-wideband tubular suspended stripline bandpass filter

A simple ultra-wideband (UWB) suspended stripline (SSL) bandpass filter based on the tubular filter structure is presented in this letter. In this design, the equivalent circuit of the proposed filter is considered as the tubular bandpass filter circuit. Then, the proposed filter could be realized by quasi-lumped elements using SSL easily. In the passband from 3.1 to 10.6 GHz, insertion loss is better than 0.5 dB, return loss is higher than 19 dB and the group delay variation is less than 0.7 ns. A good agreement between the simulation and measurement was observed.