N.I. Bobkov 1, I.A. Marchenko 2

1-2 JSC «All-Russian Scientific Research Institute «Gradient» (Rostov-on-Don, Russian)

1 ua6lac@mail.ru, 2 rostov@gradient-rnd.ru

Radiators of antenna radio monitoring systems must have stable directional characteristics in the operating frequency band. Frequency-independent log-periodic and spiral antennas are used in the meter, decimeter and lower part of the centimeter wavelength range. In the high-frequency part of the centimeter range and in the millimeter wavelength range, horn antennas are most often used, but the bandwidth of horn antennas is limited and does not exceed one and a half octaves. Therefore, the development of alternative types of antennas with frequency-independent characteristics is urgent.

One of the well-known broadband antennas, the Vivaldi antenna, is based on the radiation of an expanding slot but its characteristics are frequency dependent. But by choosing the geometry for the Vivaldi antenna, it is possible to create such conditions under which the patterns in the E-plane will remain practically constant in a wide frequency band.

To optimize the geometry, finite element modeling was carried out in the Ansys HFSS software environment for the frequency band from 0.9 GHz to 18 GHz. The profile of the expanding slot is approximated by fragments of two mating ellipses. The maximum VSWR is 2.3 at the lowest operating frequency 0.9 GHz.

The results of calculating the width of the patterns in the E plane and the antenna gain in a twenty-fold frequency band are presented. Within the operating frequency range, the gain increases from 4 dB to 15 dB, the width of the pattern in the E-plane decreases from 95° to 31.4°, but in the six-fold frequency band from 3 GHz to 18 GHz, the diagram width varies within ± 20% relative to the average value of 38.8°.

An experimental study of the model confirms the reliability of the calculated characteristics of matching and radiation. The width of the pattern in the E-plane in the frequency band from 3 GHz to 18 GHz varies from 46° to 32° with an average value of 39° with a deviation of ± 7° (± 18%). In addition, in the frequency band from 8 GHz to 12 GHz in both main planes, the diagrams practically coincide in width, that is, they are axisymmetric. Near axisymmetric diagrams are supported over a wider bandwidth, with plot width ratios in the principal planes from 1.4:1 at 5 GHz to 1.3:1 at 18 GHz.

The use of modified Vivaldi antennas in the development of broadband antenna systems makes it possible to abandon the division to frequency ranges and improve the characteristics of mass and dimensions, as well as the operational characteristics of electronic systems for various purposes.

Bobkov N.I., Marchenko I.A. Frequency independent Vivaldy antenna. Radioengineering. 2020. V. 84. № 11(22). P. 26−. DOI: 10.18127/j00338486-202011(22)-05. (in Russian)

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