Bernard Theron

A two-step synthesis of broadband ridged waveguide bandpass filters with improved performances

A quarter-wave broadband ridged waveguide bandpass filter with improved attenuation has been designed and realized. The two-step synthesis uses an equivalent network whose parameters are obtained with a multimodal variation approach that characterizes the discontinuities involved in the structure. It is shown that the frequency behavior of the filter is determined at this step by the chosen filter prototype. The structure is optimized taking into account all side effects (higher order modes, dispersion) and the rectangular to ridged waveguide transformer. Predicted data are compared with measured data and good agreement is observed. It is shown how the use of lambda /4 resonators improves the attenuation in the upper stop-band and reduces the filter volume, which is important in on-board satellite telecommunication systems. >

A new rigorous method for the determination of iris dimensions in dual-mode cavity filters

A variational method based on the mode expansion is used in order to determine the accurate physical dimensions of coupling irises in dual-mode cavity filters. By considering the concept of localized and accessible modes, a series of convergence tests are carried out in order to optimize the number and nature of modes which should be included in the numerical calculations. As a consequence, the size of matrices involved and the corresponding computation time are reduced dramatically. This approach, validated by corresponding experimental data, allows us to achieve a considerable reduction of the fabrication time of this type of filter. Actually, the filter can be tuned immediately without any correction of the calculated irises. >

Improvement in calculation of some surface integrals: application to junction characterization in cavity filter design

A rigorous method which makes it possible to reduce a surface integral to a contour integral is developed. The application of this formulation to the study of a circular-to-rectangular waveguide junction reduces the time of computation of the scattering parameters by more than 50%. The method is used to calculate the electromagnetic coupling of circular cavities by a rectangular iris. This approach, together with an optimization procedure, has allowed the direct design of a filter without any further mechanical adjustments. The results obtained are in good agreement with experimental data.<<ETX>>

Analyse et conception de filtre passe-bande en guide nervuré par l’approche variationnelle

RésuméUne approche variationnelle est présentée ici afin de caractériser diverses discontinuités uni-axiales en guide d’onde homogène. Les discontinuités en guide nervuré ont été étudiées, et les résultats sont utilisés pour la conception par optimisation des filtres passe-bande. L’introduction des notions de mode couplé et mode non couplé a permis une réduction notable des dimensions des matrices à tralter et a facilité grandement l’utilisation d’un processus d’optimisation. Les résultats théoriques ont été confirmés par l’expérimentation.AbstractA multimodal variational approach is presented for the characterization of various uni-axial discontinuities in homogeneous waveguide. A study is carried out on the ridged waveguide discontinuities, and the results have been used for the optimized design of a bandpass filter. The introduction of the notion of coupled and uncoupled modes allows reduction of the order of the matrices handled in the numerical calculation and facilitates the use of the optimization process. The theoretical results are in good agreement with measured data.