Novel Low-Loss Interdigitated Filters for Microwave and Millimeter-Wave Applications Using Micromachining Techniques

We report on the design and measurement of a new class of stripline filters for millimeter-wave applications. The novelty in this work is to suspend the interdigitated lines on a thin dielectric membrane to eliminate the dielectric losses and to render the interdigitated filter physically realizable at millimter-wave frequencies. A wide band filter with a center frequency of 13.7 GHz and a bandwidth of 45% has been fabricated. The filter exhibits a port-to-port insertion loss of 0.7dB at 13.7 GHz. This fabrication technique can be easily used at higher frequencies to result in planar low loss filters suitable for monolithic integration or surface mount devices up to 40-60 GHz.