A High-Selectivity Wideband Bandpass Dual-Mode Microstrip Filter

https://doi.org/10.1134/S1028335822020021

A half-wave microstrip resonator design with an irregular strip conductor short-circuited to the screen by its ends has been investigated. Based on the resonances of the first two oscillatory modes of this resonator, a miniaturized second-order filter with a fractional bandwidth from 40% to 90% has been implemented, which has a wide high-frequency stopband. A prototype of the designed eight-order filter based on four dual-mode resonators with a passband center frequency of 2 GHz and a fractional bandwidth of 40% has been fabricated on an alumina substrate 45.0 × 10.5 × 1.0 mm³ in size with a permittivity of ε = 9.8. The filter frequency response slopes are extremely steepness due to two attenuation poles located on the left and right sides of the passband. The experimental characteristics of the prototype are in good agreement with the data of the numerical electromagnetic simulation of the 3D model of the filter.