Dual polarized monopulse tracking feed for prime focal reflector antenna at S-band using crossed dipole elements

Monopulse tracking feed for a 1.8m prime focal reflector antenna using printed circuit crossed dipole elements is designed, developed and tested at S-Band. The requirement is to generate a low profile, high performance tracking feed suitable for dual polarized operation with high pattern symmetry for optimum illumination of a reflector. Crossed dipole antenna has been selected as feed element as it has low profile, broadband characteristics and supports dual polarization. The designed feed consists of four such elements arranged in 2×2 configuration. Feed analysis has been carried out in Ansys HFSS. Simulated performance of the feed shows a sum channel gain of 10.8dBi and difference between sum pattern peak to difference pattern peak is 3.3dB. In this design, a combination of striplines and microstrip lines are used to excite the antenna elements resulting in low cross polarization better than -30dB. Null depth in excess of 35dB is obtained in simulation for both polarizations. The antenna feed measurement has been carried out in planar near field test facility at Larsen & Toubro, Mumbai, India and measured results are presented in this paper.