Frequency-selective properties of a microstrip filter with irregular dual-mode resonators

Frequency-selective properties of a microstrip filter containing dual-mode hairpin resonators with a stepwise change in the width of the stripline conductor whose one end is connected to the screen are studied. Dependences of the design parameters and the steepness of the slopes of the amplitude-frequency response of a two-resonator filter on the filter fractional bandwidth and the substrate permittivity are considered. A large domain of the anomalous behavior of the gaps between the resonator conductors, in which the gap increases with the width of the filter passband, is revealed. The domain of values of the fractional bandwidth and the frequency band in which the design parameters of the device are realizable are determined. Good agreement between the results of the quasi-static calculation and experimental results is demonstrated.