Coupling coefficients of disk dielectric resonators and a C-band bandpass filter based on them

The coupling coefficients of disk dielectric resonators interacting through a two-conductor stripline resonator located in a rectangular diaphragm of a metal case are investigated. It is shown that the capacitive interaction of the resonators changes to inductive one when the natural frequency of the stripline resonator is lower than the frequencies of the dielectric resonators. The discovered feature allows creating miniature multi-resonator bandpass filters with additional capacitive and inductive couplings that have not only high selectivity, but also low non-uniformity of the group delay time in the passband. Using the electrodynamic analysis of the 3D model, a miniature 12th-order filter with a central passband frequency of f 0 = 3.925 GHz and a width of 45 MHz at a level of 1 dB from the minimum loss level is synthesized. In the developed filter, a two-conductor strip resonator is used not only to implement additional connections of different signs between disk resonators, but also to connect the power lines at the input and output, which improves the manufacturing process and increases the mechanical strength of the device. The characteristics of the filter confirm the prospects of the proposed design in the creation of miniature frequency-selective devices for space communication systems.

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