A wideband dual-polarized patch antenna with low profile based on differential feed for in-band full-duplex applications

This paper presents a wideband dual-polarized microstrip patch antenna with a dual-layer design to meet the requirements of high isolation for in-band full-duplex (IBFD) communication systems. The antenna improves upon the traditional square patch with four Γ-shaped probe-fed by ingeniously extending the metal strips of the Γ-shaped probes to form a cross-shaped structure, thereby exciting multiple independently tunable resonant modes. A circular ring slot is etched at the feed point to optimize the antenna impedance matching. Finally, a middle-layer circular patch is added to optimize the high-frequency impedance matching without changing the profile. By combining differential feeding technology, the antenna maintains a low-profile characteristic of 0.086 λ L (where λ L denotes the free-space wavelength at the lowest operating frequency) while achieving dual-polarized operation and high port isolation (≥42 dB), along with an impedance bandwidth of 71.5% (4.06–8.58 GHz) that surpasses most existing designs. The measured antenna realized peak gain is 8.2 dBi, with cross-polarization suppression ≤−20 dB and stable radiation pattern characteristics across the operating frequency band. This design provides a compact antenna solution with high isolation, broadband, dual polarization, and low cost for IBFD applications.