Cosecant Squared Pattern for Wide-Band Dual-polarized Antenna Array using Orthogonal Feeding Technique

This paper proposes a compact wideband dual-polarized array antenna having a cosecant-squared beam pattern for passive radar systems. In order to reduce loss at high frequencies and the number of connectors, the array antenna is realized by applying an orthogonal feeding technique that is a 3D transition configuration from microstrip to stripline. Besides, an approach to form the cosecant-squared radiation pattern based on non-uniform phase shifts but uniform amplitude coefficients of array elements is also presented. Simulation and experiment results indicate the efficacy of the feeding configuration and show that the 16-element array antenna has an impedance bandwidth (S11 < −10 dB) from 8 - 18 GHz, realized gain between 15 and 18 dBi, and the beam pattern follows the cosecant-squared curve.