A completely mechanical adjustable 2 GHz low-pass filter [Technical Committee]

This article presents the design and the realization of a mechanical tunable stepped impedance low-pass filter. The basic concept of the filter is an adjustability that completely depends on a variation of the mechanical parts. The transmission line impedance is varied by changing the height of the grounded top cover above the filter structure. Designed for a basic cut-off frequency of 2 GHz, this produces a frequency deviation of approximately 33%. This article includes a brief theoretical background, the principle steps of the filter design with Agilent ADS and Ansoft Designer, a three-dimensional (3-D) simulation set-up with EMPIRE XCcel, and an overview of the hardware realization with a comparison of the measurement and simulation results.