This paper presents a novel, independently controllable dual-polarized reconfigurable intelligent surface (RIS) unit cell for 6G upper mid-band ($7.125$–$24.25\,\mathrm{GHz}$) applications. The proposed unit cell is based on the diagonal placement of mutually orthogonal tunable radiators (loaded with varactor diodes) alongside static dual-polarized radiators. Full-wave electromagnetic simulations of the unit cell demonstrate a phase shift range of $270^{\circ}$, a maximum reflection loss of $4.5\,\mathrm{dB}$, and $61\,\mathrm{dB}$ cross-polarization isolation (XPI) within a $400\,\mathrm{MHz}$ frequency range centered at $15\,\mathrm{GHz}$. Furthermore, full-wave simulations of a $16 \times 16$ RIS panel were conducted for various reflection angles under both TE- and TM-polarized illuminations. The results demonstrate a wide-angle beam-steering capability of $\pm60^\circ$, with a maximum beam-pointing error of only $1.7^{\circ}$. The proposed RIS also exhibits accurate and stable reflection control under wide-angle excitation. A $3 \times 3$ prototype was fabricated to validate the unit cell’s performance. Measurement results agree with the simulations, yielding a $270^{\circ}$ phase shift, approximately $7\,\mathrm{dB}$ reflection loss, and $24\,\mathrm{dB}$ XPI. The proposed RIS is a promising candidate for future 6G communication systems.

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 0.086λL (where λL 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.

The study introduces a novel dual-reflector antenna featuring a modified sub-reflector design aimed at improving aperture efficiency. A cylindrical-shaped keeper is introduced to enhance the performance of the sub-reflector. The dual-reflector configuration comprises a main parabolic reflector and a modified sub-reflector, with diameters of 16.5 λ and 2.2 λ, respectively, operating at 5.5 GHz. The antenna demonstrates a bandwidth (BW) of approximately 25.4% (4800–6200 MHz). Experimental measurements indicate favorable characteristics, including low cross-polarization levels (<−25 dB), minimal back lobe levels (F/B > 30 dB), high isolation between ports (>38 dB), and VSWRs less than 1.5:1 for both port1 and port2. The antenna exhibits an efficiency of around 58% and achieves a measured peak gain of approximately 32 dBi within the operating BW.

A simple process for the design of broadband planar antennas is presented for base station applications. The process is based on a square patch above a ground plane. Only three geometric parameters are involved in the design of a dual-polarized broadband planar antenna, including the width (Ws) of the square patch, a trimming angle (θ) of the square, and the height (H) of the patch above the ground plane. By adjusting the critical parameters θ and H, an impedance bandwidth of 50% for return loss (RL) >15 dB is achieved with an isolation of higher than 35 dB. The bandwidth of the broadband planar antenna is enhanced to 67% by etching four Γ slots on the square patch. The operating mechanisms of these broadband antennas are analyzed and verified by simulation and experiment.

A low-profile, wideband dual-polarized 1 × 2 multiple-input-multiple-output (MIMO) antenna with frequency selective surface (FSS) decoupling technique is presented. Low profile is realized with two different artificial magnetic conductor (AMC) cells out of which one operates at 3.5 GHz and other with dual band at 3.1 and 4.5 GHz. The proposed antenna height is maintained at 0.125λ0 which is significantly reduced when compared with the conventional perfect electric conductor (PEC) ground plane. Wideband dual polarization is enabled by two pairs of bow-tie antenna elements surrounded by a square ring placed in the orthogonal orientation. To mitigate the near-field coupling in 1 × 2 MIMO an FSS wall is constructed with wide band stop characteristics from 2.85 to 4.75 GHz. Measured results show by inserting FSS wall vertically, coupling reduction is improved by 27 dB over the existing coupling and the antenna exhibits a bandwidth of 57.14% (2.95–4.95 GHz) for VSWR<2 with port isolation of more than 25 dB for entire band of operation.

This paper reports a bi-port, wideband, parasitic-fed, single/shared patch antenna with enhanced interport isolation for 2.4 GHz in-band full duplex (IBFD) applications. The employed parasitic feeding provides comparatively the wider impedance bandwidth and better gain for the presented antenna. The improved self-interference cancellation (SIC) levels across the required bandwidth are obtained through differentially-driven receive (Rx) mode operation. The differential Rx operation performs effective cancellation of in-band self-interference (SI) through signal inversion mechanism to achieve the additional isolation on the top of the intrinsic isolation of polarization diversity. The validation model for the presented antenna features ≥88 dB peak isolation between the dual-polarized Tx and Rx ports. In addition, the measured Tx–Rx isolation for prototype is >70 dB across the 10 dB return loss bandwidth of 100 MHz (2.42–2.52 GHz). The measured gain for each mode is better than 7.0 dBi. The novelty of this work is that compared to previously reported designs, the presented antenna offers wider impedance bandwidth and improved SIC levels in addition to superior gain performance. To the best of our knowledge, this is the first single/shared patch antenna which provides better than 70 dB interport isolation across the 10 dB return loss bandwidth of 100 MHz along with 7.0 dBi gain for Tx/Rx modes.

A compact dual-polarized monostatic antenna (single radiator for transmit and receive modes) is presented with differential receive mode operation to achieve excellent interport isolation for 2.4 GHz single frequency full-duplex or in-band full-duplex applications. The presented antenna comprises three ports radiating element (patch) and a simple 3 dB/180o ring hybrid coupler has been utilized for differentially excited receive mode operation. The 3 dB/180o ring hybrid coupler acts as a self-interference cancellation (SIC) circuit for effective suppression of RF leakage from the transmit port to provide very high interport decoupling between transmit and receive ports. A compact antenna structure has been realized by using two-layered printed circuit board through vias interconnections of both receive ports of the antenna with inputs of SIC circuit. The validation model of proposed antenna offers more than 95 dB peak interport isolation. Moreover, the experimentally measured interport isolation is better than 70 dB throughout the antenna's 10 dB return-loss impedance bandwidth (BW) of 50 MHz (2.38–2.43 GHz). Furthermore, the recorded isolation is more than 80 dB in 20 MHz BW. The implemented antenna has good radiation characteristics including nice gain and low cross-polarization levels as endorsed by measurements. Same antenna structure with microstrip-T feeds can provide DC isolated ports with same interport RF isolation performance for active antenna applications. Such antenna with DC interport isolation will avoid the requirements of additional series capacitors on transmit and receive ports of antenna.

In this paper, a microstrip fed, L-shape slot antenna for dual polarization is proposed. The two arms of the slot generate electric fields of orthogonal polarizations. By properly sectioning the slot and the feed line, ultra wideband (UWB) behavior is obtained. The measured impedance bandwidth (S11< −10 dB) is more than 8.6 GHz (112%) and 8.2 GHz (104%) for Port 1 and Port 2, respectively. The measured isolation is better than 25 dB over most of the band. The aperture field distribution justifies the dual polarized nature. A modified version which implements a band-notch over 5.1–5.85 GHz wireless local area network (WLAN) band is also presented. With a compact, single substrate design, the antenna can be useful in MIMO transmission systems, polarimetric UWB radar, high performance microwave imaging, and other future wireless communications devices.