Reconfigurable Microwave Filters Implemented Using Field Programmable Microwave Substrate

This article presents novel designs of reconfigurable microwave filters based on the recently introduced concept of field programmable microwave substrate (FPMS). Using reconfigurable FPMS substrate, significant tuning freedom of the designed microwave filters can be achieved. It allows implementation of smart filter designs with tunable center frequencies, operational bandwidths, and filter orders. Moreover, different microwave filter types are also realizable on one FPMS board with simple dynamic control. As a proof-of-concept, design steps are described for three filter types, including waveguide bandpass filter, quarter-wave-coupled bandpass filter, and waveguide bandstop filter. A good match between the simulated and measured results is presented, showing good tuning range for the center frequency and bandwidth of the bandpass filters around 2 GHz. In addition, the reconfigurability of the design allows it to switch to bandstop filters, which is a complete change in topology from a single physical design. The merits of the proposed design are reflected in the realized bandpass filter, exhibiting center frequency tuning of more than 20% along with bandwidth variability spanning three times its minimum value. Finally, a significant size reduction compared with the designs using conventional technologies is also demonstrated. With its inherent flexibility, low cost, and high degree of integration, FPMS filtering is suited to a wide variety of RF applications.