Difference-Beam Operation in a Center-Fed Dual-Polarized Parallel-Plate Waveguide Slot Array Antenna

This letter deals with the difference-beam operation in a centerfeed dual-polarized parallel-plate waveguide slot array antenna at 24.5GHz, which consists of two orthogonally arranged 20×19 arrays of radiating slot pairs. A center-feeding scheme is employed in this design. Each rectangular feeding waveguide, fed by a probe, can feed half of the radiating panel, enabling easy control of the phase difference. Experimental results show that the monopulse antenna array has a bandwidth of 12.8% for reflections below −10 dB while it produces the sum beams, and 13.3% to produce the difference beams. Port isolation between the sum mode and difference mode is above 15 dB within the working frequency band. The measured realized gain of the sum beam is 31.3 dBi at 24.5 GHz, and the measured null-depth is below −33.9 dB for both polarizations.