S.N. Boyko1, A.M. Egiazaryan2, O.V. Koryshev3

1-3 Branch of JSC “URSC” – “ISDE” (Moscow Russia)

Problem definition. Many VHF communication devices include the vibrator antennas as the simplest and technological to produce. A method for calculating input impedance and resonant frequencies of the vibrator antenna was suggested in scientific literature as an alternative to more complex numerical methods. This method is based on substitution of vibrator (symmetric and asymmetrical) by an equivalent open-ended long line with attenuation. The equivalence of this substitution implies equality of distributed line parameters and appropriate parameters of antenna. Such parameters of the line are complex propagation constant, complex wave impedance and also a correction factor to the wavenumber, which considers non-homogeneity of distributed parameters along the vibrator and capacity of vibrator’s ends. Generally engineers use empirical graphs from scientific literature for calculating the correction factor. However, it is very uncomfortable to calculate characteristics of the vibrator antenna in frequency range because the correction factor is changing with frequency. So there is a need to find an analytical form for the correction factor, which is applicable in calculating the vibrator antennas by the equivalent schemes method.

Purpose. The purpose of this paper is to get the analytical form for the correction factor, which is related to the vibrator antenna length shortening due to non-linear effects – increase in charge density on the ends of conductors and presence of end capacities.

Results. This paper shows analytical derivation of formula for the correction factor. Graphs of the dependence of the correction factor against the ratio of vibrator length to operating wavelength for fixed values of vibrator length to its radius ratio are plotted. A comparative analysis of the obtained calculated data with adopted from literature empirical ones is made. Also this paper contains calculations for resonant frequencies of asymmetrical vibrator for different ratios of vibrator length to its radius by the equivalent long line method. Appropriate experiments are carried out. As a result of the analysis of calculated and measured data it is found that application of the obtained analytical formula for the correction factor for the vibrators resonant frequencies calculation is more precise.

Practical significance. The results can be used to design the VHF vibrator antennas (including multi-frequency), which include resonant and non-resonant loads.

Boyko S.N., Egiazaryan A.M., Koryshev O.V. An analytical form for the correction factor for the vibrator antenna input impedance calculation by the equivalent long line method. Radiotekhnika. 2022. V. 86. № 7. P. 113−120. DOI: https://doi.org/10.18127/j00338486-202207-18 (In Russian)

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