Electrically small, high efficiency Ku-band monopulse Cassegrain antenna with four horn feed

An electrically small, light-weight, high-efficiency, low-sidelobe Ku-band monopulse Cassegrain antenna with a four-horn feed has been developed for the US Navy´s Target Acquisition for Ship Defense Demonstration Program. The authors report the design and performance of a 30-in-diameter (42-wavelength) monopulse Cassegrain antenna. The antenna is protected from the marine environment with a low-loss Teflon feed cover and an epoxy polyamide reflector coating. A simple rectangular four-horn feed with some modification is used to obtain high efficiency and low-sidelobe performance. The design provides 42% overall antenna efficiency in the 15.9-17.1-GHz frequency band (7.3% bandwidth) with better than -19.2-dB sidelobes at the nominal frequency. The voltage standing wave ratio at the sum and difference ports is better than 1.7 for the entire frequency band. The measured performance data are summarized, and some representative measured patterns are shown.<>