D.R. Savin1, T.Yu. Shumilov2, A.R. Khusainov3

1-3 JSC «NPP «Radiosvyaz» (Krasnoyarsk, Russia)
1 Denis.Savin.1999@mail.ru

This article addresses the critical challenge of developing high-performance bandpass filters for satellite communication input multiplexers (IMUX) in the Ku-band. The increasing demand for satellite capacity necessitates microwave components that combine miniaturization with exceptional electrical performance, including high selectivity, low loss, and outstanding stability under thermal and mechanical stress. While dielectric resonator (DR) filters based on the TE01δ mode are widely used, they possess inherent limitations, such as a restricted tuning range and susceptibility to spurious couplings, which complicate the design of compact, high-order filters.

The primary objective of this work is the design, simulation, and experimental validation of a fourth-order bandpass filter utilizing cylindrical dielectric resonators operating on the TM11δ mode. This mode was selected as a promising alternative due to its potential for high unloaded Q-factor and favorable field distribution, which contributes to a more uniform passband response and enables specific thermal compensation mechanisms. The research methodology commenced with the comprehensive electromagnetic (EM) modeling and optimization of a single resonator unit. The resonator was fabricated from a high-purity ceramic material with a high relative permittivity (ε = 24) and low dielectric loss tangent (tgδ = 7·10⁻⁵), with dimensions of 3,2 mm in diameter and 9.4 mm in height. A key design feature involved its secure mounting inside a metallic housing (18,0×12,0×12,4 mm3) using a tubular support made of fused quartz (ε = 3,7), ensuring mechanical robustness with minimal degradation of RF performance. The experimental characterization of the prototype resonator confirmed a resonant frequency of 11.388 GHz with an unloaded Q-factor reaching 11,670, which showed good agreement with the simulated value of 11.811. A detailed sensitivity analysis was performed to quantify the impact of various manufacturing tolerances on the resonant frequency and Q-factor. Furthermore, the thermal stability was investigated, revealing a temperature coefficient of frequency (TCF) of approximately -116 kHz/°C for a housing made of aluminum. A theoretical model for TCF calculation, incorporating the material's temperature coefficient of linear expansion (αL = 6,9·10⁻⁶) and the temperature coefficient of permittivity (τε = 5·10⁻⁶), was presented and validated. Based on the optimized resonator, a fourth-order filter was designed, fabricated, and tuned. The final filter demonstrated a center frequency of 11.034 GHz with a 55.8 MHz bandwidth (0.5% fractional bandwidth). The measured group delay variation within the passband was less than 7 ns. The filter successfully underwent a series of environmental tests, including thermal cycling and vibration, confirming the stability of its performance parameters. The results substantiate the proposed TM11δ-based DR filter as a compact, reliable, and high-performance solution for advanced satellite communication payloads, effectively addressing the limitations of conventional designs.

Savin D.R., Shumilov T.Yu., Khusainov A.R. A Ku-band filter based on dielectric resonators. Achievements of modern radioelectronics. 2026. V. 80. № 3. P. 118–126. DOI: https://doi.org/10.18127/j20700784-202603-13 [in Russian]

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