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Abstract-This paper presents an approach for the design and optimization of pseudo-gradual transitions in circular waveguides using the genetic algorithm (GA). The characterization of these transitions is carried out by the mode-matching method. This method, associated with the generalized scattering matrix technique, leads to determine the reflection coefficient on the useful band of the studied structures and to observe their frequential behavior. The GA is employed to optimize the choice of geometrical parameters by minimizing a cost function, corresponding to the maximum magnitude of the reflection coefficient in the band. The selection of the most relevant parameters allowed an improvement of the performances for the optimized components. Results of optimization are given for both two and four-section transformers.

In this paper, we apply robust optimizers (i. e. the simplex method and the genetic algorithm) to rectangular ridged waveguide filter design. We extend the use of the simplex method to the design of high performance filters in narrower relative bandwidth. The proposed optimization tool is successfully applied to narrower bandwidth of four pole and six pole rectangular ridged waveguide filters. The results outperform those produced by the conventional simplex method and genetic algorithm.

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In this work, a compact finite-difference time-domain (FDTD) algorithm with a memory-reduced technique is proposed for the dispersion analysis of rectangular waveguides either fully or partially loaded with longitudinally-magnetized ferrite. In this algorithm, the divergence theorem is used to eliminate the longitudinal components of the electric and magnetic flux densities. The mobius transform (MT) technique is applied for the first time to obtain the equations relating the magnetic field to the magnetic flux density in a ferrite medium. Some examples are presented to validate the obtained algorithm with numerical results: good agreement is obtained with a significant reduction in the memory space requirement compared to the conventional algorithm.

This paper presents a novel quintuple-mode wideband filter based on a circular Substrate Integrated Waveguide (SIW) cavity. To implement this filter, a pair of two metallic perturbation vias loaded around the diameter resonator line is used. An Elliptic Dielectric Resonator (EDR) was introduced in the middle of the cavity to shift certain resonant modes and restrain the higher-order modes. The optimal dimensions and dielectric permittivity of the EDR are investigated. A single SIW resonator filter has been designed, manufactured, and measured as an experimental example to verify the proposed design. Simulation and measurement results agree with 51.7% of fractional bandwidth at 10.1 GHz central frequency, with one transmission zero (TZ) at the lower frequency side and four TZs at the upper side.

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