Transmission Line Dual-Mode T-shaped Resonator With All Short-Circuited Ends

An analysis of the resonant frequencies of a transmission line dual-mode T-shaped resonator, which has three ends, and all of them are short-circuited, has been carried out. The resonator has no input, therefore the traditional even/add analysis method cannot be applied to it and this resonator has not been studied until now. It was established for the first time that the transmission line resonator can simultaneously have two types of oscillations, dual-mode and simple oscillations. Moreover, these oscillations alternate with each other. In the considered T-shaped resonator, simple oscillations have odd numbers $f_{1},f_{3}$, and dual-mode oscillations have even numbers $f_{2},f_{4}$, Dual-mode oscillation with frequency f2 is working one. It is surrounded by simple oscillations f1 and f3, which in this case are parasitic. Stepped-impedance transmission line segments (SILS) were synthesized for this resonator. It using as a structural element of a T-shaped resonator made it possible to remove parasitic oscillations with frequencies f1 and f3 from a working dual-mode oscillation f2. The established alternation effect is also extended to the triple-mode resonator, in which triple-mode oscillations alternate with simple oscillations.