Shorting-Pin-Inspired Coupling Reduction in Dual-Band Dual-Polarized STAR Antenna

A dual-band, dual-polarized simultaneous transmitand receive antenna, achieving very high isolation without the use of a differential feed and coupler, is presented in this letter. First, the antenna design is composed of two circular patches that are excited orthogonally by a micro-strip feed line to generate dual-polarized characteristics with moderate isolation levels. Later, shorting pins were used at an offset position to achieve high isolation by balancing the mutual capacitive and mutual inductive coupling. The fabricated antenna is measured, and the results demonstrate that the minimum measured isolation values are 47 dB and 45 dB, within the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula>10 dB impedance bandwidth of 2.37 GHz to 2.422 GHz and 2.724 GHz to 2.764 GHz, respectively. Notably, the proposed design exhibits dual-band characteristics, and shorting pins are capable of improving isolation at both frequencies simultaneously. According to the far-field measurement, the antenna shows broadside radiation, with a measured cross-polarization level of less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula>23 dB for the lower band and less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula>35 dB for the upper band. The proposed configuration offers advantages, such as being low-profile, single-layer, with a simple feed, and dual-band, providing high isolation, making it a promising candidate for full-duplex communication applications.