Theory on asymmetrical coupled‐parallel‐line transmission and reflection zeros

Abstract

SummaryThis paper treats an innovative methodology on the synthesis mechanism of the coupled‐parallel‐line (CPL) transmission zero (TZ) and reflection zero (RZ). The CPL structure under study is configured as a reflection type distributed arbitrarily loaded stub circuits. On the basis of the equivalent Z‐matrix analysis, the CPL input impedance theoretical model is established. Mathematical analysis is performed to predict accurately the TZ and RZ frequency shifts in function of the CPL physical parameters. The input impedance behavioral model in function of asymmetrical CPL load parameters is determined. The TZ and RZ existence conditions are established. Then, the characteristic equations illustrating the TZ and RZ fundamental formulas in function of the CPL coupling coefficient and characteristic impedances are examined. Furthermore, innovative graphical representations of the TZ and RZ existence conditions in function of the CPL parameter ranges are explored. The developed CPL model was validated with different cases of simulated microstrip proof of concept. As expected, a good correlation between the TZ and RZ frequency shifts from the analytical calculations and simulations is obtained. The developed CPL model is useful for the TZ and RZ frequency shifts fast monitoring during the Radio Frequency (RF)/microwave circuit design phase. Copyright © 2017 John Wiley & Sons, Ltd.