Design of Hybrid Folded Rectangular Waveguide Filters With Transmission Zeros Below the Passband

The design and physical implementation of hybrid folded rectangular waveguide filters providing multiple transmission zeros (TZs) below the passband are considered in this paper. These structures offer great flexibility to locate the TZs in a wide frequency range. Different implementations have been considered, each one offering certain advantages in terms of ease of manufacture, number of TZs, and their separation from the passband. A simple design procedure is also described. Measurements of a manufactured five-pole filter prototype and simulations fully validate the novel configurations proposed in this study.