S.А. Khodenkov - Ph.D. (Eng.), Associate Professor, Reshetnev Siberian State Aerospace University, Resource Center for Collective Use «Space Vehicles and Systems» (Krasnoyarsk) E-mail: hsa-sibsau@mail.ru

It is well known that bandpass filters are essential elements of modern radio communication, radar and navigation systems. One of the main requirements for microstrip filters is diminutiveness, technological effectiveness, as well as high-frequency selective properties. In the present study we investigated filters constructed on the microstrip resonators with grounding close to the center of the strip conductors. All the proposed structures have through square-shape holes in dielectric substrate with the height equal to the substrate thickness h and with the area S = 0,04 mm2. These holes are filled with the conductive material that is why all the conductors are grounded at the base. The amplitude-frequency characteristics (AFCs) of the filters of the fourth, sixth and eighth orders (N = 4, 6, 8) are obtained by the synthesis using electrodynamic numerical analysis of 3D models. In this connection same substrate with high dielectric constant ε = 80 and thickness h = 1 mm were used for objective comparison of the frequency-selective properties in numerical calculations. Filters setting is made by «manual» parametric synthesis at a fixed relative bandwidth width - Δf/f0 = 30%. The first construction used regular resonators with rectangular strip conductors, the second miniaturized construction used irregular resonators with folded C-shape strip conductors. The increase of links number in the construction of filters, built both on regular and irregular resonators is accompanied by a significant increase of power suppression at stop band, as well as by a significant increase of the steepness of slopes of bandwidths. Moreover in first construction the pair of power attenuation poles on the left and right of the bandwidth is observed on the AFCs of filters with an odd number of resonators, in the second structure, on the contrary, of filters with even number of resonators. Minimum loss of power Lmin in the bandwidth of three examined filters (N = 4, 6, 8) of the first structure constituted ~0,5 dB, ~0,9 dB, and ~1,2 dB, respectively. Similar minimal filter loss (N = 4, 6, 8) of the second construction increased slightly ~0,6 dB, ~0,9 dB, and ~1,3 dB, respectively. Both filters of 8 order have strong power suppression at low-frequency stop band: while using in structures regular resonators - more than 100 dB, while using irregular cavities - more than 130 dB.

 

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