V.N. Egorov1, Le Quang Tuyen2

1 East-Siberian Branch VNIIFTRI (Irkutsk, Russia)

2 INRTU (Irkutsk, Russia)

The characteristics of a coaxial resonator with a capacitive measuring gap in the central electrode and their correspondence to the results of numerical simulation are studied experimentally. The internal dimensions of the resonator, including the gap, were determined using a special procedure. The tuning range of the resonant frequency when the gap changes from 0.02 mm to 3.2 mm is
93...547 MHz. The intrinsic Q-factor of the resonator in the tuning range varies from 3500 to 6400. A resonator with an unfilled measuring gap and with a dielectric sample in the gap is considered.

The results of numerical simulation of the resonator, approximation of its characteristics and comparison with experiment are presented. The difference between the experimental resonant frequency of the resonator and the results of numerical simulation in the range of measurement gap variation from 1 mm to 3.2 mm is less than 1.3%.

The influence of such factors causing deviations of the experimental resonator from the ideal cylindrical shape as corrugation and conical deformation of the membrane-wall is estimated experimentally using high-precision numerical simulation. Under the influence of corrugations, the resonant frequency of the resonator increases, which corresponds to a decrease in its real height. The concept of “effective” height in accordance with a resonator with a flat membrane-wall and its calculation formula are introduced. Replacing a conical deformed membrane in the calculations with a flat effective surface at an effective height leads to an error in the calculation of the resonance frequency of no more than 0.06%.

Experimental research and numerical calculation of a resonator with a dielectric inclusion in the measuring gap showed that the measured samples and the known methods of their placement were not verified. The roughness of the surface of the samples creates residual microgaps between them and the surfaces of the electrodes. It is proposed to place a sample between electrodes with known gaps in order to eliminate this effect.

The peripheral region of the dielectric sample outside the electrodes has a little effect on the frequency and Q-factor of the resonator. This reduces the requirement for knowing the exact diameter of the sample to be measured and centering it in the gap.

Egorov V.N., Le Quang Tuyen. Numerical and experimental study of coaxial cavity resonator with a measuring gap. Radiotekhnika. 2022. V. 86. № 6. P. 141−150. DOI: https://doi.org/10.18127/j00338486-202206-17 (In Russian)

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