Reseach On The Efficient Element Antenna In The Limited Scanning Phased Array

Based on the simple introduction of GBR-P at home and abroad literature, and requirements of the antenna element for high performance, the efficient antenna element in a widely-spaced limited-scan phased array with a flat-topped radiation pattern in X-Band is investigated in this paper. This kind of the efficient antenna element has the advantages of small aperture and high gain. The main research is divided into five parts.(1)A wavedirector is designed, it can make the gain value of antenna element which diameter less than 38 mm increase 4dB than the general antenna element which has the same diameter, and the 3dB lobe width decreases about 20°.(2)Two kinds of circular polarization are designed, one is a stepped-septum polarizer in stepped-septum polarizer in a circular waveguide with the coaxial feed in side face, the other is square waveguide with the coaxial feed in bottom surface.(3)Three kinds of efficient antenna elements in a widely-spaced limited-scan phased array are investigated and the diameter of the antenna elements are all less than38 mm. One is cylindrical efficient antenna element, it consists of a wavedirector, two circular waveguides. The other is circular polarization horn efficient antenna element with the coaxial feed in side face, which can work in 2GHz bandwidth. It consists of two coaxial input ports, a circular polarizer, a conical horn and wavedirector. When the port feed, it forms a right-handed circularly polarized wave, when the other port feed, it forms a left-handed circular polarized wave. Another efficient antenna element is improved by the second element considering the actual application, it consists of a wavedirector, a circular polarizer, a square-circular transitional waveguide, a conical horn, two match steps and two coaxial input ports in bottom surface. Its performance is almost no difference with the second efficient antenna element.(4)A limited-scan uniform phased-array antenna composed of above described 7 by7 efficient horn antenna elements is simulated by the software Ansoft HFSS, the element spacing is 1.3 wavelengths. And the radiation pattern is flat-topped, the gain value is 12.3dB, the sidelobe level is less than- 18 dB, 3 dB lobe width is 40.6 °, and the axial ratio is less than 3dB in this range. Based on the ideas of small array instead of a large array, it can be find the grating lobes are suppressed to- 27 dB, which make the performance of the large array better.(5)Three-dimensional moment method with RWG basis function is used to numerical calculate for the radiation pattern and AR of the horn efficient element, center element feed and all the elements feed in 7?7, and the calculated results of the radiation pattern and the axial ratio compared with the simulation results which simulated by software Ansoft HFSS based on the finite element method. It can be find that the results are almost consistent. Finally the physical antenna is finished, and reached the technical indicators.