A Compact Dual-Polarized (CP, LP) With Dual-Feed Microstrip Patch Array for Target Detection

A planar antenna is designed to replace complex structures of many rat-races and 90° hybrids used in conventional target detection antennas for receiving radar signals. The proposed antenna has 2 × 2 microstrip patch antenna arrays with dual feeding to radiate symmetric polarizations in the 9.375 GHz (X-band). The sum (Σ) pattern with circular polarization is implemented through a sequence feeding at port 1. The simultaneous feeding of port 2 radiates a difference (Δ) pattern in all linear polarizations. Thus, the proposed antenna is compact, planar, and has a simple comparator circuit. Measurement results verify the designed prototype, showing that the antenna has a null depth of over 34.5 dB in all polarizations, a peak sum gain 4.51 dB at 9.375 GHz, and a 3 dB axial-ratio bandwidth of 160 MHz.