Dual polarised microstrip patch antenna using feedforward isolation enhancement for simultaneous transmit/receive applications

This paper presents a method for increasing the isolation between transmit and receive ports of a dual polarised microstrip patch antenna in order to enhance its performance in single frequency simultaneous transmit/receive applications. A feedforward circuit signal cancellation scheme is demonstrated which is shown to improve the dual polarised antenna port isolation performance to be better than -60 dB while leaving the antenna radiation pattern largely unaltered when compared to a uncompensated (i.e. conventional) dual port microstrip patch antenna with -35 dB port isolation. Experimental results for a prototype system operating at 1 GHz are presented.