Dimensional Design of Dual Mode Waveguide Multiplexers

In this paper, a systematic design procedure is described for manifold type multiplexers formed by the classical circular dual mode waveguide filters. The design procedure starts with cascade synthesis of lumped quadruplet version of the filters with inverter couplings. Then the LC resonators are converted into SC transmission line (SCTL) resonators. The whole circuit is then impedance scaled by inverters at ports for realization of resonators as waveguides with desired cross-sectional dimensions thus forming a quadruplet with four waveguide resonators coupled by inverters. The resonator pairs on source and load side are treated as dual modes of single waveguides reducing the four waveguides into two. Then the in-line inverters are converted into constant reactances for realization as irises. This stage causes electrical lengths of the resonating dual modes to differ. They are equated by introducing proper tuning reactances to complete design of the circuit model of the filter. Several X-band and Ku band manifold type multiplexers are designed and optimized by using the circuit models of the filters. Then field models of the filters and multiplexers are formed on EM simulators and fine tuned for implementation.