Design and evaluation of a high selectivity combline bandpass filter

Quasi-planar combline bandpass filters have been realized in suspended substrate stripline. The coupling between non-adjacent resonators and the composite effect of N quasi-TEM modes excited from N-coupled lines are considered. The design approach is briefly described. The performance evaluation of bandpass filters centered at 2.050, 2.125, 2.375 and 6.750 GHz, with bandwidths of 100, 250, 250 and 500 MHz, respectively, is reported.