Enhancing the Out-of-Band Response of Hybrid Wide-Band Filters in Rectangular Waveguide

The objective of this paper is to describe a number of different techniques to enhance the out-of-band performance of wide-band rectangular waveguide filters. In particular, we discuss the use of mixed inductive and capacitive (hybrid) couplings, in conjunction with a staircase configuration and E-plane T-junctions, to yield a significant improvement both in the out-of-band response and in the filter selectivity. In addition to theory, we also discuss the performance of several filter prototypes, thereby fully validating the new filter topology.