14 December 1992 Inadequacy of coupled equations for forward traveling waves in case of large waveguide perturbations
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Proceedings Volume 1929, 17th International Conference on Infrared and Millimeter Waves; 19290O (1992) https://doi.org/10.1117/12.2298141
Event: 17th International Conference on Infrared and Millimeter Waves, 1992, Pasadena, CA, United States
Abstract
To test the validity of coupled mode equations for the complex amplitudes of forward traveling waves in the case of large waveguide perturbations in highly overmoded waveguides we performed a comparison of coupled wave equations, not including and including reflected waves, with scattering matrix computations for the example of a short, single-period 60 GHz TE02-TEm mode converter. The calculations show the inadequacy of the simple forward-wave coupled mode equation approximation to describe the behaviour of high-order parasitic modes which are close to cutoff. All forward and backward traveling waves that can propagate in the interior of the converter should be included. If one of the two main modes in a mode transducer is relatively close to cutoff, Bragg resonances occur so that as in the case of mode conversion at abrupt changes of the waveguide cross-section the use of a scattering matrix code is required since the scale length of the waveguide perturbation is small compared to the wavelengths of the different modes.
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J. Pretterebner, J. Pretterebner, } "Inadequacy of coupled equations for forward traveling waves in case of large waveguide perturbations", Proc. SPIE 1929, 17th International Conference on Infrared and Millimeter Waves, 19290O (14 December 1992); doi: 10.1117/12.2298141; https://doi.org/10.1117/12.2298141
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