Design and Optimization of Rectangular Waveguide Filter based on Direct Coupled Resonators

The waveguide filter structure is treated by two softwares (HFSS (High Frequency Structure Simulator) and CST (Computer Simulation Technology)). Numerical example is given in this article to demonstrate, step by step, the application of the approach to the design of resonator, direct coupled waveguide and microstrip filters based on electromagnetic (EM) simulations. For this design procedure, the filter structure is simulated by successively adding one resonator at a time. To continue the work illustrates how to design a fourth order coupled resonator based rectangular waveguide circuit in the traditional way. With a large number of variables, such tuning work consumes a lot of time and the convergence of the final result is not guaranteed. A fourth order X-band bandpass filter with a center frequency of 11 GHz and a fractional bandwidth FBW = 0,0273 is designed using this procedure and presented here as an example. The simulated results by CST are presented and compared withthe results simulated by a high-frequency structure simulator. Good agreement between the simulated HFSSand simulated results by CST is observed.