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 2x2 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.