Compact Via-Coupling Fed Monopulse Antenna With Orthogonal Tracking Capability in Radiation Pattern

In this letter, a compact monopulse antenna operating at 10 GHz is presented. The feed network consists of four rat-race couplers, which generate sum and difference patterns in orthogonal radiation planes (azimuth and elevation). The focus is on improving the performance by improving the matching circuit to generate in-phase and out-phase excitations while also maintaining a very high null-depth, which is applicable for tracking purposes. The electromagnetic energy is transmitted from the feed network to the radiators through the via-coupling structure. Using the symmetrical via-fed patch array results in the low-mutual coupling between the antenna ports. A prototype of the proposed antenna is manufactured on a printed circuit board and is tested. A suitable agreement between the measurement and simulation results is obtained. The results show a -10 dB impedance bandwidth of 2.1%, as well as -24 and -20 dB null depths on the elevation and azimuth planes, respectively, in the difference mode of operation.