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The various CEM methods in FEKO make it well suited to the simulation of non-radiating structures. Waveguide circuits are an excellent example of this kind of problem and this application note highlights some of the benchmark simulations of waveguide components that have been done with FEKO.
Waveguide Magic Tee Coupler
The magic tee is a four-port, 180° hybrid splitter and like all of the coupler and splitter structures, the magic tee can be used as a power combiner or a divider. It is ideally lossless, so that all power injected in to the sigma or delta port can be assumed to exit the remaining ports, without ohmic or other losses detracting energy. A FEKO model of a WR-90 waveguide magic tee was simulated in FEKO while driving the sigma port with a waveguide source. The vector arrows indicate that the fields at the output ports are indeed in phase.
Dual-Mode Waveguide Cavity Filter
Waveguide filters come in a wide variety of designs. Guglielmi et al  published a design for a cavity based Ku-band dual-mode waveguide filter. This filter has a pass-band of approximately 11.0 to 11.2 GHz, with input reflections (S11) around –20 dB in this band. The transmission zeros on either side of the pass-band are also clearly visible in the computed response. Electric near-fields in the cavities were calculated at the 11.1 GHz resonant frequency and are shown below.
Ez field components inside the dual-mode waveguide filter at 11.1 GHz
Dielectrically Loaded Waveguide Filter
Shigesawa et al.  describe an evanescent-mode waveguide filter with dielectric blocks forming two parallel cut-off waveguide paths. The proposed filter is modelled in FEKO with the Finite Element Method (FEM) and driven with a FEM modal port. FEKO automatically computes the dominant mode for this port and uses this mode to excite the filter. Figure 5 shows a lateral cut-plane view of the model with metallic elements in orange and dielectric blocks in blue. As this filter is designed for a wide band of frequencies, FEKO’s Adaptive Frequency Sampling (AFS) technology is applied to effectively select the minimum number of frequency points that will accurately characterise the filter’s response.
 M. Guglielmi, P. Jarry, E. Kerherve, O. Roquebrun, D. Schmitt, “A New Family of All-Inductive Dual-Mode Filter”, IEEE Transactions on Microwave Theory and Techniques, Vol. 49, No. 10, Oct. 2001, pp. 1764-1769.
 H. Shigesawa, M. Tsuji, T. Nkao, K. Takiyama, “Two-Path Cutoff Waveguide Dielectric Resonator Filters,” IEEE Transactions on Microwave Theory and Techniques, Vol. 37, No. 7, July 1989, pp. 1105 – 1112.
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