This paper presents a novel miniaturized multi-evanescent-mode resonator. The resonator is achieved with a coaxial cavity. This coaxial cavity essentially has a direct short connection at one end and is connected with several lumped capacitances at the other end. The key technology of the resonator is the usage of multiple evanescent-modes of TM (transverse magnetic wave) modes. Due to the combined effects of the evanescent mode and multiple modes, the size of the resonator is greatly reduced. In this paper, the theory of resonator is discussed in detail. To verify the correctness of operation, the resonator is used in experimental measurements conducted to realize a third-order band-pass filter based on SIW (substrate-integrated waveguide) technology. The measured results are found to agree with the theoretical values.
