Communication science et technologie
Volume 13, Numéro 1, Pages 27-48
2015-01-01
Coupleurs Branchline Tem Et Quasi-tem A Lignes Coaxiales Classiques
Auteurs : Djamal Lachachi . Nadia Benabdallah . Nasreddine Benahmed .
Résumé
Abstract In this article a novel type of Branchline coupler convenient for high power applications and for high power measurement systems is presented, analyzed and designed. Our novel type of Branchline coupler is realized with traditional coaxial TEM and quasi-TEM lines and does not have any geometrical discontinuities. For instance, this coupler was designed to operate at 450 MHz. The insertion loss of the coupler S31 and direct S21 paths is better than −3.73 dB over the 14.3 % bandwidth from 100 to 800 MHz. Return loss S11 and isolation S41 are better than −14.14 dB over this bandwidth. To reach this objective and these results, it was necessary to determine numerically the electromagnetic parameters of the TEM and quasi-TEM coaxial lines. Also we developed a set of accurate closed-form formulas for the electromagnetic parameters of quasi-TEM coaxial lines. Our analytical expressions, deduced from rigorous analysis by the finite element method and curves fitting techniques, can be easily implemented in CAD simulation tools, to design others circuits (couplers, filters…) operating at different frequencies and using the quasi-TEM coaxial line. Our results obtained for two TEM and quasi-TEM Branchline couplers were validated by our simulations done under MATPAR and CST environments.
Mots clés
Keywords : Quasi-TEM Branchline coupler / inhomogeneous coaxial ligne / electromagnetic parameters / developped expressions / scattering parameters [S] / finite element method.
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