Numerical Synthesis of Simple Waveguide Mode Sensors

A computer aided design of a rectangular waveguide H10-H20-mode sensor is demonstrated, which consists of a broad waveguide section with two asymmetric inductive irises, an H-plane asymmetric T-junction and an asymmetric junction to a smaller rectangular guide. The theory is based on field expansion into orthogonal eigenmodes which includes higher-order mode excitation in the computations. Numerical optimization of the design parameters achieves an H10-H20-mode cross-talk attenuation of over 50 dB. Measurements at a simple prototype are in close agreement with theory.