A novel miniature suspended stripline filter

Concept, design, and results of a novel miniature suspended stripline (SSL) filter type based on an interdigital filter structure with quasi-lumped elements are presented. The filter is realized in a metal channel of 4.25 mm/spl times/5 mm. Compared to a standard SSL resonator, length is reduced by about 75%. A three resonator filter at 7 GHz with a 450 MHz bandwidth is demonstrated, having a filter length of only 12 mm and losses of about 1.4 dB, including 18 mm of excess transmission line and the transitions to coaxial line. Further examples are a three-resonator filter at 11 GHz and a 8 GHz five-resonator filter.