Monopulse antenna array based on three-modes with orthogonal radiation beams

A compact multi-layer substrate integrated waveguide (SIW) monopulse antenna array operating at X-band is proposed. The structure consists of four stacked layers, including one layer for the radiating 4 × 4 rectangular microstrip antenna elements and two SIW layers for the comparator network. The sum and difference modes provide orthogonal radiation patterns in the azimuth and elevation planes. The two SIW layers of the comparator network feature a compact multi-feed design while maintaining high isolation between the antenna ports. To validate the proposed antenna concept, silmulations and measuremets are carried out. The obtained resuts show good performnces, a −10-dB impedance bandwidth of 13.45 % (9.35–10.7 GHz) for the sum and difference ports, better than 30 dB isolation between the antenna ports, the difference radiation patterns better than −38 dB null-depth. The comparison between the simulated and measuremed results shows a good agreement.