Easy-to-Fabricate Embedded Negative Coupling Structure for Post-Loaded Dielectric Resonator Filter

This paper presents a negative coupling structure that can be fabricated with ease and can be embedded in a surface mountable resonator filter. Unlike the existing negative coupling structures, adding the presented structure can be executed without increasing the number of fabrication steps. In addition, one of the unique features is that surface-mountable filters can adopt the negative coupling structure presented in this paper as it does not necessitate creating slots on the outer surfaces of filters. A complete design approach for the negative coupling structure is provided. For demonstrating the presented negative coupling structure and its design method, we have designed a fourth-order surface-mountable post-loaded cavity filter with a pair of transmission zeros. The measured frequency response exhibits a pair of transmission zeros, which verifies that the presented coupling structure has a negative coupling value.