Investigation of Microwave Filters Based on Multimode Resonators

Multimode microwave resonators with a rectangular strip conductor split at one end and grounded to the base at the opposite end, as well as ultra-wideband bandpass filters based on them, were studied by means of numerical electrodynamic analysis of their three-dimensional microstrip models. When calculating amplitude-frequency characteristics of all microwave devices, monolithic substrates with a high dielectric constant $\varepsilon=80$ (microwave material - TBNS ceramics) were used. It is shown that in multimode resonator, the folding of a strip conductor in the form of a meander is accompanied by additional resonances to its passband. It is possible to organize an additional channel of power passage in the considered resonators, which significantly improves their selective properties. There is also a possibility to implement ultra-wideband bandpass filters with a relative bandwidth of at least 100% based on the proposed multimode microstrip resonators. Filters can be designed using both one resonator and several counter-directional resonators in the device. All synthesized microwave structures are given with constructive dimensions.