Association of HPWRs and DBRs for a High Rejection C-Band Filter With Post-Tuning Elements

This letter focuses on a new topology of bandpass filter (BPF), based on the combined use of different resonators. The filter is a C-band fourth order filter based on the association of hybrid planar waveguide resonators (HPWRs) and dual behavior resonators (DBRs). The association of these particular resonators was chosen so that the filter would benefit from their high-Q SIW cavities and intrinsic transmission zeros at finite frequencies. The present letter also suggests a method to adjust the filter response after fabrication, in order to compensate for the technological dispersion, and thus meet stringent specifications. Adjustment can be achieved by controlling transmission zeros for each resonator. The mixed filter with an embedded post-fabrication tuning elements was built on a standard ceramic substrate and tested to demonstrate the underlying concept. Experimental results agree well with simulation results.