Low-cost monopulse antenna using bi-directionally-fed microstrip patch array

A new technique for realising a simple low-cost monopulse antenna using a symmetrical bi-directionally-fed microstrip patch array is described. The antenna is designed and demonstrated at Ka-band. Two squinted beams are radiated from a bi-directionally fed microstrip patch array, and a sum/difference pattern is synthesised using the in-phase and out-of-phase signals achieved using a hybrid ring coupler. The measured return loss is better than 10 dB at the sum and difference port, and the depth at broadside is more than 30 dB.