Re-entrant filter analysis using transmission line equivalent models

Presented in this manuscript is the analysis method and a thorough validation of the method for a novel filter technology called the Re-entrant filter. This material augments the work performed on this type of filter in reference [l]. For this work a software program was developed which incorporated those elements of the analysis detailed in this manuscript (See Appendix A). Validation of the analysis model was achieved by comparing those results with measurements made on a prototype unit, and against results from a finite element analysis. The analysis model was improved over the previous work [l] by including the effects of frequency dependent coupling between microstrip and slotline. The computation of slotline wavelength and impedance, as well as a better capacitive gap model were included. The effects of mitering the slotline bends on re-entrant filter response were investigated, as well as, the effects of cascading 2 re-entrant filter sections. The analysis method yielded excellent agreement with measured data and with the finite element annuluses as will be shown in this document.