B.A. Belyaev – Dr.Sc. (Eng.), Professor,

Reshetnev Siberian State University of Science and Technology (Krasnoyarsk)

E-mail: belyaev@iph.krasn.ru

S.A. Khodenkov – Ph.D. (Eng.), Associate Professor, 

Head of Electronics and Telecommunications Department, 

Reshetnev Siberian State University of Science and Technology (Krasnoyarsk)

E-mail: hsa-sibsau@mail.ru

N.A. Shepeta – Ph.D. (Phys.-Math.), Associate Professor, 

Reshetnev Siberian State University of Science and Technology (Krasnoyarsk) E-mail: nashka116@mail.ru

The paper presents the results of theoretical and experimental studies of microstrip three-mode resonators and ultra-wideband filters based on them. All calculated amplitude-frequency characteristics of the devices were obtained by means of numerical electrodynamic analysis of their 3D models. Substrates with dielectric constant ε = 80, thickness h = 1 mm (material is TBNS ceramics) and

ε = 9.8, h = 1 mm (material is polycor) were used in devices synthesis during calculations. The first microwave device is a threemode resonator with a П-strip conductor on a dielectric substrate, consisting of two extended parallel segments that are connected to each other by a wide segment grounded from the inside to the base through open-end hole in the substrate. In fact, such promising resonator in its frequency-selective properties is already an ultra-wideband filter with a relative bandwidth Δf/f0 = 50% formed by resonances of its three lowest oscillation modes. To verify the accuracy of numerical electrodynamic analysis results, an experimental model of two-tier filter of the 6-th order based on a three-mode resonator was made. There is a qualitative coincidence of calculations with measurements on amplitude-frequency characteristic. Compared to the synthesized model with Δf/f0 = 50%, the experimental filter band is narrowed by several percent due to the large diameter of holes made compared to the diameter in the model. High frequency-selective filter properties are explained by the expanded high-frequency stopband and the steep slopes of the passband. The relative bandwidth of the two considered devices can be significantly increased, for example, making twice larger, using additional extended conductor segment in the resonators which is orthogonally aligned with a wide segment. At the same time, an open-end hole is located at the free end of this segment. It should be noted that such additional segment length increase in threemode resonator allows expanding the passband of filters implemented on its basis. The developed ultra-wideband filter based on modified three-mode resonator also has high frequency-selective properties. Thus, the article presents great possibilities for the implementation of microstrip filters with relative bandwidths from 50% to 100% on substrates with low and high dielectric permittivities.

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