Design and Realization of Compact C- Band Monopulse Feed Using Additive Manufacturing

A four horn monopulse tracking feed is used to generate tracking signal in a C-band tracking application. Choke flanges are incorporated at the aperture of array of pyramidal horns in order to achieve better pattern symmetry and reduction in sidelobes. An in-line polarizer is used against each horn to achieve multiple polarization i.e. VP, HP, RHCP and LHCP. The polarizer consists of an in-line waveguide structure - one fixed and one rotating waveguide sections to generate all four polarizations. Monopulse comparator is used to generate sum and difference signal. In order to realize the feed in a compact form factor, complex shapes, e.g. diagonal bends, have been used and manufacturing of these complex shapes would have been possible using additive manufacturing technology (Metallic 3D Printing). This made the feed very compact and light weight. Processes have been evolved to overcome the challenges with additive manufacturing for achieving desired accuracies. The feed assembly has been tested in a standard Antenna Test Range. Return loss of the system is achieved as better than −15dB and null depth of difference pattern is also better than −35dB. There has been a close agreement observed between the simulated and measured results.