Dual-Band Dual-Polarized Slotted-Patch Antenna for In-Band Full-Duplex Applications

This letter presents a dual-band dual-polarized slotted-patch antenna with high isolation and high gain for in-band full-duplex applications. The antenna consists of a double differential-feed <inline-formula><tex-math notation="LaTeX">$45^\circ$</tex-math></inline-formula>-rotated square patch with four capacitively coupled <inline-formula><tex-math notation="LaTeX">$\Gamma$</tex-math></inline-formula>-probes. The proposed design utilizes the TM10 resonant mode of the patch for the lower resonance, whereas four trapezoidal slots are symmetrically etched on the patch to generate the upper resonance. By examining the feeding locations, the four slots can be excited simultaneously, yielding a high-gain radiation at the upper resonance. A design operating at 2.45/5.25 GHz has been optimized with two dual-band rat-race couplers employed to realize the double differential-fed scheme. The fabricated prototype with a profile of 0.06<inline-formula><tex-math notation="LaTeX">$\lambda _{\text{2.45-GHz}}$</tex-math></inline-formula> yields a measured 10 dB return loss bandwidth of 2.40–2.52 GHz and 5.09–5.41 GHz, an isolation of <inline-formula><tex-math notation="LaTeX">$\ge$</tex-math></inline-formula>44 and 41 dB, a gain of 8.5 and 9.2 dBi, and a cross-polarization level of <inline-formula><tex-math notation="LaTeX">$\le$</tex-math></inline-formula>−32 and −22 dB for the lower and upper bands, respectively.