A. V. Gudelev1, O. A. Kurdyumov2, V. E. Sagach3
1–3 JSC "Research Institute of Space Instrumentation" (Moscow, Russia)
This article is devoted to an urgent topic: obtaining information about the position of the phase center (PC) of elliptically polarized antennas (EPA). Knowledge of the position of the antenna PC is necessary when designing antenna arrays, irradiators of mirror and lens antennas, phase navigation systems.
In the article, on the basis of the method proposed earlier by the authors for determining the coordinates of the antenna PC, three types of EPA have been studied: a turnstile, a spiral antenna and a microstrip antenna.
Expressions for the amplitude and phase of the electric field have been obtained on the basis of electrodynamic analysis for a half-wave turnstile. According to these formulas, phase curves are constructed depending on spherical angles – zenith and azimuth. Using these curves, the stability of the position of the PC has been calculated. It has been shown that the turnstile antenna has a stable PC: its displacement does not exceed 1% of the wavelength.
Spiral antennas, due to their broad band, are used as irradiators of broadband mirror antennas. For spiral antennas, based on calculations, the dependences of the position of the PC on the diameter of the base, the number of turns and frequency have been obtained. It has been shown that the position of the PC of spiral antennas significantly depends on the design parameters and on the frequency. Experimental study of the phase properties of a broadband (from 1.1 GHz to 1.7 GHz) mirror antenna irradiator has been carried out. According to the phase curves, the positions of the PC for each of the frequencies have been calculated. According to the data, the average position of the PC is calculated and after moving the antenna to the calculated position, the zenith phase dependences are again removed. The change in the phase curves after moving the antenna shows that, on average, the PC is aligned with the origin. This method can be used to combine the PC of the irradiator with the focus of the parabolic antenna.
In general, the results obtained indicate the fallacy of the statement, that the spiral antenna PC is located at a distance equal to 1/3 of its height from the base, and show a significant dependence of the position of the PC on various design parameters.
In microstrip antennas with single-point excitation, the position of the PC significantly depends on the design parameters, especially with small base diameters.
A microstrip antenna with four-point excitation has a much more stable position of the PC, independent of the azimuth angle. A significant dependence of the position of the PC of such an antenna on the height of the substrate has been shown. At the same time, the position of the PC of this antenna does not depend at all on the azimuth angle. Due to this property, four-point microstrip antennas are most often used in precision satellite navigation systems.
The data obtained in the article on the position of the PC and its stability allow the developers of antenna devices to carry out operational control and optimization of the properties of the irradiators of mirror antennas and choice of the design of precision satellite navigation antennas.
Gudelev A.V., Kurdyumov O.A., Sagach V.E. Investigation of the phase center position of elliptically polarized antennas. Antennas. 2022. № 4. P. 26–32. DOI: https://doi.org/10.18127/j03209601-202204-03 (in Russian)
- Antenny ellipticheskoj polyarizatsii. Sb. statej. Per. s angl. pod red. A.I. Shpuntova. M.: IIL. 1961. (in Russian)
- Knyazev N.G., Kurdyumov O.A., Sagach V.E. Prostoj metod opredeleniya koordinat fazovogo tsentra antenny. Antenny. 2020. № 1. S. 28–33. (in Russian)
- Kugushev A.M., Golubeva N.S. Osnovy radioelektroniki. M.: Energiya. 1969. (in Russian)