Dual-polarized pattern-reconfigurable array antennas are desirable for applications requiring both polarization diversity and wide-angle beam coverage. In this communication, a dual-polarized pattern-reconfigurable array antenna with independent beam control in the horizontal (H-pol) and vertical polarizations (V-pol) is proposed. The array element adopts a compact shared-aperture configuration with a size of 0.50λ0×0.51λ0×0.18λ0 at 3.5 GHz and integrates an H-pol patch antenna and a V-pol Yagi-Uda antenna. The two radiators are excited through decoupled ports, and each supports three beam-pointing states at -25°, 0°, and +25°, yielding nine dual-polarized beam modes through independent state combinations. A 1 × 8 array prototype is designed, fabricated, and measured. The measured -10 dB impedance bandwidths are 260/530 MHz for H-pol and 520/450 MHz for V-pol when the element beam is directed toward 0°/+25°, respectively. The proposed array achieves ±60° wide-angle beam scanning in both polarizations. By steering the element beams toward large scanning angles, the array gain is enhanced and the sidelobe levels are significantly suppressed in both polarizations. The proposed design is among the few array-type dual-polarized pattern-reconfigurable antennas with independent pattern reconfiguration in both polarizations.
A self-detecting and self-healing reconfigurable intelligent surface (RIS) system with modular large-scale expandability is proposed. The proposed RIS system comprises a 2-bit reconfigurable reflectarray (RRA), dedicated fault detection boards (RIS-FDBs), and a real-time optimizer (RIS-RTO). The 2‑bit RRA employs a 10×10 sub-array architecture that can be modularly expanded and reduce the risk of damage. The RIS-FDB enables simultaneous control and real-time monitoring of element status through 116 control and detection channels. The RIS-RTO is integrated into the RIS system and performs on-site computation for phase-coding configuration optimization. The characteristics of damaged RIS elements are investigated, and a Python-based optimization platform is developed to employ a genetic repair algorithm to restore the RIS far-field performance by optimizing the phase-coding configuration. Based on element-failure information, the optimization platform generates optimal phase distributions and visualizes 2D far-field radiation patterns and 1D radiation cuts to highlight performance improvements. A 5.8 GHz 10×10 2-bit sub-array RRA was developed and expanded to a 20×20 array to experimentally validate the proposed self-healing scheme. The system achieved a measured gain of 20.9 dBi and a 2D beam scanning range of ±60°, with gain improvements over the corresponding damaged states of 1.1, 6.6, and 3.5 dB at 10%, 30%, and 50% element failure rates in single-beam operation, respectively, and 3.9 dB at a 30% failure rate in dual-beam operation, while effectively suppressing sidelobes.
In this communication, a deep learning-assisted method is introduced for phaseless near-field to near-field (NFTNF) transformation, specifically designed to reduce the measurement time required for multi-height and multi-frequency scanning. A joint height-frequency embedding network (JHFE-Net) is proposed, where the target height and frequency information are represented by the height feature pattern and frequency feature pattern and embedded into the network. These feature patterns condition the network to predict the near-field at the target height and frequency, which serves as the output of JHFE-Net. Notably, these feature patterns are learnable implicit latent representations that are optimized during the training process of the JHFE-Net. With the proposed JHFE-Net, the original single-input, multiple-output problem is transformed into a multiple input, single output task, thereby facilitating network training. Numerical and experimental examples demonstrate the validity of the proposed method. The source code and data are publicly available at: https://github.com/DongHaoHan/TAP-Near-Field-Transformation.
A fabry-perot cavity antenna (FPCA) is realized by employing a wideband, low loss, and polarization insensitive frequency selective rasorber (FSR) as a superstrate. The FSR consists of a lossless layer and two upper lossy layers being co-designed with the primary antenna source. Dispersive analysis using leaky wave theory shows that broadside radiation is possible from about 5.5 GHz which corresponds to the transmission band of the low scattering superstrate. To realize polarization and pattern agility, the antenna is designed with a multi-port array feeder at the centre of the structure. This feed system is enabled by substrate integrated waveguide (SIW) technology, which demonstrates high isolation in excess of 45 dB when considering dual-linearly polarized radiation, for example. Artificial magnetic conductors (AMCs) were also employed and integrated within this bottom feeding layer to reduce the in-band radar cross section (RCS) of the antenna. Simulation and experimental results demonstrate a reduced RCS from 1.5 GHz to 10 GHz, defining a bandwidth (BW) of 147.8% which advances the state-of-the-art. In addition, when compared to other low scattering planar antenna systems, our developed configuration is compact, offers gain enhancement, high isolation, low cross-polarization levels, and an angularly stable scattering response. Application for the FPCA include radar systems, scattering reduction, and polarization-diverse scenarios.
Efficient radiation and low radio-frequency (RF) exposure remain challenging for user-terminal antennas in lossy proximity to the human body. This communication proposes an optimization-oriented method that uses an internal-multiport, current-based formulation retrieved from a single full-wave characterization to investigate the trade-off between radiation efficiency and specific absorption rate (SAR). Radiation efficiency and SAR are evaluated from the port-current solution of the internal-multiport formulation, and the design goals of impedance matching, efficiency enhancement, and SAR control are formulated as a multi-objective optimization solved by the nondominated sorting genetic algorithm III (NSGA-III), forming a closed-loop of evaluation, optimization, and selection. Four platform-integrated smartwatch cases illustrate an achievable region between on-tissue radiation efficiency and peak SAR in the user scenario considered in this work, showing that peak SAR can vary over a range at a fixed efficiency. Using this method, a tri-band smartwatch antenna is developed, achieving radiation efficiencies 2.4 and 2.25 times those of the reference antenna at 2.44 GHz and 3.5 GHz, respectively, while reducing peak normalized SAR by 14% and 35%. A prototype was fabricated, and measurements validated the simulations.
In this paper, a novel method based on bias-integrated multi-resonant arrays is proposed for multifunctional metamaterials. In contrast to conventional active designs with a single active band, the proposed metamaterial could independently manipulate the in-band and out-of-band functions by providing frequency-shiftable and function-reconfigurable responses, respectively, through changing its electrical biasing voltage and physical rotation (or incident polarization) angle. Under each manipulation mode, the proposed multi-resonant structure provides destructive interference windows with different paths for the in-band, and by changing the biasing voltage of the loaded active semiconductor components, the resonance can be switched among these paths, thereby shifting the in-band operating frequency from 4.7 GHz to 5 GHz. After rotating the physical angle of the structure, the proposed design not only switches the out-of-band function from co-polarized reflection to polarization conversion, but also provides cross-polarized and circularly polarized outputs for the lower (around 4.2 GHz) and higher (around 5.4 GHz) out-of-bands, respectively. Additionally, owing to the proposed bias-integrated architecture and frequency compensation strategy, the in-band and out-of-band reconfigurable functions are nearly independent and exhibit negligible mutual influence. It is noted that, due to the developed quasi-symmetrical structure, similar frequency-switchable and function-reconfigurable responses could be achieved under the two orthogonal polarized incidences (TE/TM and -45°/45°). Finally, a prototype was fabricated and measured, and the effectiveness of our approach was validated through theoretical analyses, numerical simulations, and experimental measurements.
This paper presents a novel dual-band dual-directive beam lens antenna that integrates beam scanning and high gain for unmanned aerial vehicle (UAV) base station applications. The proposed design combines a parallel-plate Luneburg lens and a gradient-index (GRIN) lens using frequency-selective surfaces (FSS) to simultaneously support UAV tracking and communication around 15 GHz and satellite backhaul around 60 GHz. Within the low frequency band, the FSS acts as a reflective boundary. Then the structure performs as a parallel-plate Luneburg lens, enabling wide-angle beam scanning (±60°) with fan-beam radiation for UAV communication. Within the high frequency band, the FSS becomes transparent, transforming the structure into a GRIN lens that produces a high-gain fixed beam with a gain of 25 dBi for satellite links. The antenna achieves wideband performance with over 40% impedance bandwidth around 15 GHz and over 40% around 60 GHz, while maintaining low cross-polarization (<-30 dB) and sidelobe levels (-13 dB at 15 GHz, -18 dB at 60 GHz). A 3D-printed prototype validates the design, demonstrating compact integration of both functionalities without performance compromise. This work provides a practical solution for next-generation UAV base stations requiring simultaneous access and backhaul capabilities in a single aperture.
This work proposes a dual-wideband and dual-polarized shared-aperture antenna (SAA) with small frequency ratio (FRa) of 1.5:1 for 28/43 GHz millimeter-wave applications. Each dual-polarized SAA element consists of a 2×2 high band (HB) array and a single low band (LB) element, each coupled to a specific orthogonal feed via an aperture slot. A coupled open-short stub and via cavity are employed to widen the bandwidth in both bands, besides improving out-of-band gain suppression. LB operates from 23.5 to 32.3 GHz (with 31.5% of fractional bandwidth) HB operates from 38 to 48.8GHz (24.9%). Besides featuring dual-wideband operation and dual polarization, this SAA array also offers a high out-of-band suppression (of more than 27 dB), cross polarization discrimination (XPD), and isolation (both at least 25 dB) for two operating bands. In addition, the inverse radiation-suppression index (RSI) is also used to measure the stopband performance between the two operating bands. The RSI of this proposed SAA array achieve 0.62. Finally, a stable broadside radiation pattern is also ensured throughout the operating bandwidth.
Magnetic induction (MI) communication demonstrates excellent performance in complex environments such as underground, and it is therefore attracting growing research interest. MI communication has been proven to be an effective solution to extend the communication range in a lossy medium. As a near-field communication technology, MI communication has a limited communication range. Meanwhile, MI communication currently lacks a well-defined methodology for defining its boundary distance, hindering systematic guidance for the design and optimization of MI communication systems. The existing field demarcation based on electromagnetic wave (EMW) exhibits deficiencies in accounting for the structural characteristics and application scenarios of magnetic antennas. In this paper, we propose the MI energy density-based boundary demarcation and provide an explicit expression. To adequately account for the influence of magnetic antenna structure and dimensions on field demarcation, this study employs a thin circular loop antenna for modeling. We establish the field demarcation within a homogeneous medium and subsequently extend the findings to the inhomogeneous medium. To better depict the medium’s inhomogeneity, the inhomogeneous scenario has been expanded to include two distinct configurations: one with the antenna positioned above the layered medium in half-space, and another where it is embedded in the layered medium. Compared to the classical demarcation, the result proves that our demarcation can better inscribe the boundary in the low-frequency range. Additionally, we investigate the influence of operating frequency, medium type, antenna size, and medium thickness on the boundary. By analyzing the results, we identified that operating frequency and the medium type are the key factors influencing the demarcation.
This work presents a low-dispersive leaky-wave antenna based on an inductive metasurface over a grounded slab radiating through a dense medium. A quasi-optical system consisting of a pillbox coupler feeds the metasurface and launches the low-frequency-dispersive leaky-wave mode. The dispersive behavior of the leaky-wave antenna is governed by the permittivity of the dense medium and the surface impedance of the metasurface on the grounded dielectric slab. A transverse resonance technique is employed to engineer the dispersive characteristics of the leaky-wave mode and to determine the resulting pointing direction of the radiated energy. The antenna concept is numerically and experimentally validated with an antenna pointing at 27.2° along the E-plane in the band (27–33 GHz). A dense prism-shaped dielectric with a relative permittivity of 12 radiates the energy into free space. The final prototype has a size of 23.25×18.1×5.9λ30 where λ0 is the wavelength at the central frequency (30 GHz). The pointing direction of the measured radiation pattern in elevation changes by less than 0.5° across the considered band and by less than 1° in the full Ka-band (26.5–40 GHz), validating the low dispersive property of the antenna. The measured, realized gain is 25.9 dB with a radiation efficiency of 41% at 30 GHz.
Integrated sensing and communication (ISAC) is envisioned as a key enabling technology for sixth-generation (6G) wireless networks. The centimeter-wave band offers a favorable trade-off between propagation coverage and spatial resolution, making it particularly suitable for ISAC systems. Research on ISAC in the centimeter-wave band is still in its early stages, and the corresponding channel characteristics have not been fully characterized. In this paper, ISAC channel measurements are conducted for indoor static and dynamic scenarios at 10 GHz. Shared multipaths corresponding to objects in the environment can be observed, and multipaths exhibit birth-death phenomenon and spatial consistency. The shared clusters between sensing and communication channels are observed and extracted, and the shared cluster power ratios are obtained. To more intuitively reflect the degree of similarity between sensing and communication channels, angle similarities in the azimuth and elevation directions are studied. In addition, statistical properties of sensing and communication channels are derived and analyzed, including space-time-frequency (STF) correlation functions (CFs), delay spread, angular spread, coherence distance/time/bandwidth, and stationary distance/time/bandwidth. By comparing the statistics of sensing and communication channels, the differences between these two channels are thoroughly explored, revealing their distinct characteristics in STF, delay, and angle domains.
Radar sensors operating at millimeter-wave and sub-terahertz frequencies are essential for emerging applications in autonomous navigation, human–machine interaction, etc. Yet, the realization of compact, low-cost radar-on-chip systems has been constrained by poor antenna efficiency and strong self-interference between co-located transmitter and receiver paths. To overcome the aforementioned constraints, this work presents a 3D-integrated dual-port circularly polarized metasurface antenna fabricated on a 16-nm FinFET chip and vertically stacked with ultra-thin quartz superstrates above the RF circuits. The two ports radiate opposite handedness to enable polarization duplexing, providing isolation without spatial separation, couplers, or active cancellation. Measurements at D-band demonstrate >28 dB TX–RX leakage suppression from 134–142 GHz, stable circularly polarized radiation with broadside axial-ratio performance, and a measured peak radiation efficiency of 68% at 140 GHz. The proposed antenna-in-package architecture allows compact, scalable integration of the radiating aperture and mm-wave circuitry for interference-resilient sensing platforms.
Evaporation ducts strongly affect over-the-horizon electromagnetic propagation in marine environments, but conventional radar sea clutter inversion methods often require labeled environmental data and calibrated radar parameters. This paper proposes a physics-informed unsupervised framework for retrieving range-dependent evaporation duct height (EDH) profiles from uncalibrated measured sea clutter. The core of the method is a differentiable parabolic equation (PE) operator embedded in a closed-loop training process, which links EDH-profile prediction, physics-based forward propagation, and sea clutter reconstruction. A low-dimensional B-spline EDH parameterization mitigates ill-posedness, while a physics branch and a constrained residual branch collaboratively model the dominant propagation trend and structured local mismatch. Dynamic weighting and a physics-prioritized progressive training strategy further stabilize unsupervised optimization. Experiments on unlabeled measured sea clutter show that the proposed method reconstructs the main observation-domain clutter structures and retrieves physically consistent range-dependent EDH profiles. External consistency analysis using WRF reference fields, sparse buoy observations, and ablation studies confirms the effectiveness and interpretability of the framework.
Ambient RF energy typically arrives from unknown directions and has varying polarization states, which can cause considerable power loss in conventional single-polarized or high-directivity rectennas. To address this problem, this article presents a low-profile omnidirectional dual-polarized rectenna array for 2.45 GHz ambient RF energy harvesting (RFEH). The main contribution is a planar dual-polarized architecture that combines a circular microstrip patch operating in the TM02 mode for vertically polarized omnidirectional harvesting with a five-element meandered dipole array for horizontally polarized omnidirectional harvesting. Different from reported dual-polarized omnidirectional rectennas that use vertically protruding radiators for the vertically polarized channel, the proposed rectenna keeps the profile to 0.033λ0. Each antenna element is directly conjugate matched to its Schottky diode at the RF port, so external impedance-matching and feeding networks are removed. This element-level impedance co-design reduces insertion loss and circuit footprint. A prototype was fabricated and measured in a microwave anechoic chamber. The rectenna achieves a maximum PCE of 33.5% at 2.45 GHz with an input power of -20 dBm. Additional azimuthal-angle, polarization-angle, and simultaneous multi-source measurements verify stable RF energy harvesting under incident conditions closer to practical ambient RFEH scenarios. These results show that the proposed architecture provides a compact rectenna front end for low-power IoT energy-harvesting systems.
A novel millimeter-wave substrate-integrated ultra-wideband quad-mode-composite complementary source antenna (CSA) is proposed in this paper. By introducing L-shaped slots and grounded metallic vias into a dual-mode-composite CSA, i.e. a magnetoelectric (ME) dipole, a quad-mode-composite scheme combining an electric dipole mode, a patch mode, an aperture mode and a parallel dipole mode is developed. Meanwhile, two nonradiative modes supported by the proposed antenna are also employed to realize filtering characteristics without need of additional filtering structures. A 4 × 4 array is designed, fabricated and tested, which confirms an ultra-wide impedance bandwidth of 112% for |S11| below −10 dB that can cover the whole millimeter-wave FR2-1 bands and stable radiation performance. Due to the fully substrate-integrated geometry and excellent radiation characteristics, this work provides a new method of improving the bandwidth performance of millimeter-wave antenna arrays and thus is valuable to future millimeter-wave applications.
