Remote Reconfiguration of Microwave Filters Using Dielectric Tuners

The objective of this article is to explore the use of dielectrics to reconfigure remotely microwave filters in rectangular waveguide. To start, we study experimentally the phase shift that is achievable using dielectric tuning elements in a rectangular waveguide. We then compare the results obtained with the performance of standard metallic tuning cylinders and screws. Next, the passive intermodulation (PIM) behavior of dielectric tuning elements is investigated experimentally. The PIM results obtained using dielectrics are then compared with the ones of metallic tuning elements. After that, the measured results for a filter tuned with a number of different dielectric tuning elements are discussed to identify the required relation between cavity size, dielectric constant, and tuner diameter. As a proof of concept, we then design, manufacture, and test two filters, one in WR75 and the other in WR90. Both simulated and measured results are then presented clearly demonstrating that the structures discussed can indeed be reconfigured (or tuned) both in terms of filter center frequency and bandwidth. Finally, computer-driven linear actuators are connected to the dielectric tuners, and the remote tuning capability is successfully demonstrated.