Bandpass filters using electrically‐coupled TM010 dielectric rod resonators

Abstract

AbstractThe authors previously described the design of shielded TM010 dielectric rod resonators (below referred to as “TM010 resonators”), a new configuration of small‐size resonators for microwave frequencies. This paper describes the design of bandpass filters using coaxially oriented electrically‐coupled TM010 dielectric rod resonators. First, the resonant frequency of electrically‐coupled TM010 resonators is analyzed by applying the Ritz‐Galerkin method to the integral equations that express the boundary conditions. This method is shown to be effective in numerical calculation of the coupling coefficients and center frequency of the coupled resonators and the resonant frequencies for inserted TM010 resonators which are required for filter design. Next the characteristics of the coupling probe which effectively produces the strong coupling of the axially symmetric TM010 mode of resonators and suppresses the excitation of the higher modes are determined experimentally, making it possible to estimate the center frequency for a filter which takes the variation of the resonant frequency produced by the excitation and coupling hole into consideration. Finally, design of 2‐ and 3‐stage filters of various bandwidths at 2.7 GHz demonstrates the suitability of the approach. Relative bandwidths of 1 to 10%, low losses of. 15 to. 6 db, and absence of spurious responses over bands wider than 1 octave are obtained.