High-Isolation, Low Cross-Polarization, Dual- Polarization, Hybrid Feed Microstrip Patch Array Antenna for MPAR Application

This paper presents a high-isolation, low cross-polarization dual-polarized patch antenna for multifunction phased array radar applications. Its hybrid feed design has been implemented, and the vertical and horizontal polarizations are excited by a balanced-probe feed and a slot-coupled feed, respectively. Simulations and measurements have demonstrated an input isolation of 45 and 43 dB between the horizontal and vertical ports, respectively. For further improvement in the cross-polarization level, the image feed method is also implemented, and a <inline-formula> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula>-element array made up of designed elements with image configuration has been fabricated. The simulated and measured S-parameter and radiation patterns of the horizontal and vertical polarizations of the designed <inline-formula> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula>-element array are presented and the measured cross-polarization level of less than −37 dB is achieved. To examine the performance of the designed element in an array, a <inline-formula> <tex-math notation="LaTeX">$3\times 3$ </tex-math></inline-formula>-element array of designed <inline-formula> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula>-element subarray is fabricated and tested. In the <inline-formula> <tex-math notation="LaTeX">$6\times 6$ </tex-math></inline-formula>-element measurements, −35.4 and −36 dB cross-polarization levels for horizontal and vertical polarizations are achieved, respectively. Also, using the measured embedded element patterns, the cross-polarization level lower than −36 dB for scan angles up to 45° is achieved.