Microwave and Optical Technology Letters, Volume 56, Issue 4, pages 814–818, April 2014.
Maksym A. Popov 1,2, Igor V. Zavislyak 1,2,D. V. B. Murthy1 and Gopalan Srinivasan1,*
- Department of Physics, Oakland University, Rochester, MI.
- Department of Radiophysics, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine.
The nature of dielectric resonance and its utility for a magnetic field tunable band-pass filter have been studied in a polycrystalline disk of nickel ferrite. The lowest order dielectric resonance manifests as two modes corresponding to clockwise and counter-clockwise polarization of the microwave fields. Under the influence of a static magnetic field perpendicular to the disk plane, one of the modes show a decrease in frequency whereas the other shows an increase in frequency. With increasing H, the frequency separation increases. Band-pass filters for operation at 19, 30, and 35 GHz have been designed and characterized. The filter central frequency has been controlled with proper choice of disk dimensions. The filter frequency is tuned with H, by 2–7%. As the filter frequency is well above the ferromagnetic resonance frequency expected for the static magnetic fields, the overall losses are small with the insertion loss ranging from 2 to 5 dB. Theoretical estimates of H-tuning of dielectric resonance and pass-band are much higher than measured values, indicative of potential for further improvement in filter performance. The ferrite filters are of importance for use in the K and Ka-band communication devices.
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