A ultra wideband dual-polarized antenna with high isolation degree for passive radar application

This paper presents an ultra wideband (UWB) dual polarization antenna with high polarization isolation for passive radar system The antenna is composed of a modified Vivaldi antenna and a folded dipole log periodic antenna. Based on the respective structural characteristics of the printed Vivaldi antenna and the folded dipole log periodic antenna, they are placed orthogonally without touching each other, which form two orthogonal polarization channels and can achieve high polarization isolation between the channels. The radiator shape of traditional Vivaldi antenna is modified and simplified to further reduce the electromagnetic coupling between two polarized radiators. The planar folded dipole log periodic antenna is fed by UWB Microstrip tapered line Balun, and a vertical through hole is introduced to connect the parallel double line of Balun and the coplanar stripline (CPS) at the input terminal of the folded dipole log periodic antenna. The two polarization ports of the antenna are welded by coaxial line and microstrip line. The dual polarization antenna is designed, optimized, fabricated and tested within the range of 3 GHz ~ 8 GHz. In the investigated frequency range, the polarization isolation of the simulated dual polarization antenna is greater than 30 dB, and the average polarization isolation is about –35 dB.The gain of Vivaldi antenna polarization port increases from 2.82dBi to 9.49 dBi, and the gain of folded dipole log periodic antenna polarization port increases from 5.21 dBi to 8.56dBi. A large number of experimental tests and analysis are carried out on the fabricated dual polarization antenna, and the test results are close to the simulation results, which prove the effectiveness of the proposed dual polarization antenna. In view of the printed circuit implementation method and structure characteristics of the dual polarization antenna designed in this paper, the scheme has the advantages of low cost, simple design and good polarization characteristics, so it is suitable for the application of anti radiation missile guidance radar and electronic reconnaissance.