Telecommunications and Radio Engineering

ISSN for PRINT: 0040-2508

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2001, Volume55

Issue 3

102 pages

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Ye. M. Ganapolskii
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine, 12, Academician Proskura St., Kharkov 61085, Ukraine

A new method for measuring extremely low dielectric losses of the microwave (MW) electromagnetic field in dielectric crystals was proposed and implemented. These losses are associated with the phonon absorption (PA) of the electric field caused by the nonlinear (anharmonic) properties of a crystal phonon system. The method is based on the use of a spherical dielectric resonator (SDR) made from the crystal being measured. The electromagnetic "whispering gallery" oscillations with the super-high quality factor (Q-factor) are excited in this resonator in the case where the quasi-optical parameter ζ = kα√ εμ » 1, where k is the wave vector of the electromagnetic wave in open space, α is the sphere radius, ε is the permittivity and μ is the magnetic permeability of sphere material. A theoretical background of the SDR method has been provided. A SDR-based technique for measuring extremely low dielectric losses in solids over the 8-mm wave band at different temperatures including the low temperature is described. The results obtained by measuring dielectric losses temperature dependence in sapphire, ruby, quartz and fluorite crystals at a frequency of 36.7GHz within the temperature interval varying between room temperature and that of liquid helium are presented. Possible mechanism responsible for the microwave electromagnetic field residual absorption in dielectric crystals are discussed.

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