Nontrivial nearfield topologies in nano-optics refer to nearfield configurations embedded within singularities or topological defects, providing an ideal platform to explore integrated optoelectronics and higher-dimensional topological physics. Exciting such field topologies relies on selection rules related to various conserved quantities. Unfortunately, existing algebraic rules focus primarily on scalar singularities in nano-optical (e.g., plasmonic) systems and largely neglect the vectorial nature of the fields. More critically, these rules remain phenomenological. Given the intrinsic link between conserved quantities and symmetries, here we establish a unified selection rule using group theory that govern the excitations of nontrivial field topologies across three photonic spin states in generic nanophotonic systems. This rule can act as building blocks for constructing selection rules for exciting and engineering higher-dimensional field topologies (embedded within vectorial singularities and quasiparticles). These rules are derived purely from symmetry arguments and are therefore rooted in first principles. The proposed rules further predict two novel physical effects in plasmonic systems: spin-orbit splitting of vortices and multidimensional nested vortices. Phase-resolved in-situ measurements of nested multidimensional plasmonic topologies well demonstrate our findings. Our group-theory-based approach can serve as a versatile framework for engineering symmetry- and singularity-related phenomena-like circular meron lattices and plasmonic quasicrystals-in diverse wave systems.

This work presents an inverse design method for a pi-type phase-shift circuit using deep learning and particle swarm optimization (DL-PSO). The proposed framework enables simultaneous control of amplitude and phase in reconfigurable arrays, including reconfigurable intelligent surfaces. The DL-PSO method resolves the non-unique mapping problem and enables precise control of both amplitude and phase. An external PSO loop optimizes fixed structural parameters by evaluating amplitude performance over a full 360 degrees phase range. A prototype operating at 2.8 GHz was fabricated and measured. It achieves full-range phase tuning with a maximum amplitude fluctuation of 0.6 dB and an average phase error of 1.92 degrees. Accurate amplitude control is also achieved at multiple target levels across the 360 degrees phase range, with average amplitude and phase errors of 0.16 dB and 1.76 degrees, respectively. The proposed method is scalable for reconfigurable array applications such as beam shaping and null steering.

Leaky-wave antennas (LWAs) are prominent candidates for millimeter-wave (mmW) applications due to their high-gain radiation and simplified topologies. While the inherent frequency-scanning capability of LWAs is advantageous for radar sensing and detection, it constitutes a critical limitation for point-to-point communications requiring stable beam alignment. For the fundamental suppression of beam scanning, a design strategy based on an air-filled micro-coaxial line (MCL) is proposed to construct a fixed-beam LWA. The beam stability is achieved by exploiting the naturally low-dispersive quasi-TEM mode of the MCL combined with a dispersion-compensating E-plane probe transition. The antenna comprises an E-plane probe transition and a composite triple-slot array designed for miniaturization and high gain, both fabricated by micro-metal additive manufacturing (M-MAM) and assembled with a computer numerical control (CNC)-machined split-block waveguide fixture. Benefiting from the independence of the coaxial mode from cross-sectional dimensions, the design achieves an ultra-compact cross-section of 0.4×0.08 λ02, which is the smallest among reported mmW fixed-beam LWAs. Experimental results demonstrate a -10-dB impedance bandwidth of 54.9–58.5 GHz with a negligible beam deviation of 1.9° and a peak gain of 11.3 dBi.

A saddle-pattern dual circularly polarized (CP) dielectric resonator antenna (DRA) with a broad half-power beamwidth (HPBW) and axial ratio beamwidth (ARBW) is proposed in this letter. A circular patch fed by two orthogonally placed dual L-probes is utilized for dual-polarized operation, and a cylindrical dielectric resonator (CDR) excited by the patch is located on the top of the proposed DRA, which is used as the main radiator. An optimized air slot is loaded in the CDR to strengthen the side radiation, and an electromagnetic bandgap structure surrounding the slot-loaded CDR is used for reducing normal radiation and further enhancing low-elevation radiation, thereby achieving a saddle-shaped wide beam for the proposed antenna. The proposed DRA exhibits a saddle-shaped pattern in both E- and H-planes, with HPBW of more than 160 degrees and 3 dB ARBW exceeding 175 degrees in 19.7 GHz to 22.7 GHz. Based on the proposed DRA element,the left-hand circular polarization 1 & times; 8 array antennas with two feeding networks corresponding to scanning angles of 0 degrees and 70 degrees are designed, fabricated and measured, demonstrating a +/- 70 degrees scanning ability with only 1.23 dBic low gain fluctuation and a 3 dB axial ratio bandwidth of 14.1%.

In this paper, a dual-layer metal-only Huygens' metasurface (HMS) based on air medium is proposed to achieve independent phase and amplitude control of linearly polarized electromagnetic (EM) wave for sidelobe suppression in a transmissive metasurface configuration. The unit cell consists of two identical layers, each containing an inner concentric extended split-ring slot (CESS) and an outer concentric split-ring slot (CSS). Phase modulation based on Huygens' principle is realized by adjusting the physical parameters of the slots to manipulate the orthogonal electric and magnetic resonances, while amplitude is controlled by rotating the structure to modulate the co-polarized transmission based on its polarization selectivity. To validate the design concept, a phase and amplitude modulated transmissive metasurface called TM-II is designed and fabricated. For comparison, a base design employing phase-only modulation called TM-I is also realized. The measured results show that the TM-II with amplitude tailored to follow the Taylor distribution improves the sidelobe level (SLL) by 1.6 dB in the xoz plane and 6.1 dB in the yoz plane compared to the phase-only modulation design. This proposed HMS offers a new approach for independent phase and amplitude control, which could be applied to point-to-point communications, satellite systems, and high-power applications.

This paper presents two hybrid bandpass filters (BPFs) based on spoof surface plasmon polaritons (SSPPs) and double-grating rectangular waveguides (DG-RWG) for millimeter-wave applications. A Ka-band BPF with embedded split-ring resonators (SRRs) provides an independent tunable notch band within the passband. A W-band BPF achieves flexible bandwidth control through independent parameter tuning of DG-RWG and SSPP-RWG structures. Dispersion analysis shows that DG-RWG operates in the fast-wave region and determines the lower cut-off frequency. In contrast, SSPP-RWG transitions from the light line to the slow-wave region and defines the upper cut-off frequency. Experimental results show that the Ka-band BPF has a passband from 27.8 to 36.6 GHz, a notch band from 31.2 to 32.9 GHz, an insertion loss of <0.44 dB, and a return loss of >14 dB. The W-band BPF achieves an 80.1-93.8 GHz bandwidth with ~0.57 dB insertion loss and return loss >10 dB. Both designs employ all-metal RWG structures to achieve low loss and high power handling.

The increasing antenna density and limited clearance in modern smartphones severely restrict the bandwidth and isolation of frame antennas. While the large space on the smartphone back cover has been commonly used for implementing standalone planar antennas, much less effort has been devoted to harnessing its potential to assist the design of frame antennas. This work proposes a filter-integrated back cover strips concept, in which dedicated strips are designed for different antennas and operation bands to introduce additional resonant modes and controllable coupling paths, enabling simultaneous decoupling and bandwidth enhancement, while filters prevent cross-band interference and enable compact integration. A quad-antenna frame system covering the 4G B41 (2.5-2.69 GHz) and 5G N79 (4.4-5.0 GHz) bands is designed and experimentally validated. With the proposed back cover strips and only 0.75-mm frame clearances, the -6-dB impedance bandwidths are expanded by 2.1~2.4× in the B41 band and 2.4~3.6× in the N79 band, while the corresponding sideband efficiencies are improved by 7.2~10.4 dB and 3.2~5.6 dB, effectively activating frequency regions that were previously difficult to utilize. Meanwhile, the isolations are improved to above 11.2 dB across both bands. The proposed concept offers an effective and practical solution for high-performance multiple-input multiple-output (MIMO) frame antennas in smartphones.

In this work, an amplitude-induced phase control method is proposed to achieve phase modulation by performing vector synthesis of two components with a tunable amplitude ratio. With a fixed phase difference between the components, continuous phase tuning of the synthesized wave is achieved by adjusting their amplitude ratio. A dual-output element based on a guided-wave structure is designed, enabling both outputs to provide a full 360 degrees phase shift. In this element, tuning the amplitude ratio also controls the phase difference between the two outputs, enabling polarization manipulation of the transmitted wave. A high-gain full-polarization-tunable transmitarray antenna is subsequently designed, fabricated, and measured. Simulated and measured results validate the effectiveness of the proposed phase control method. The transmitarray antenna demonstrates significant advantages in aperture efficiency and polarization tunability. Furthermore, the proposed method requires no active components, avoiding static power consumption and thus making it suitable for power-constrained scenarios such as satellite communications, unmanned aerial vehicles (UAVs), and Internet of Things (IoT) applications.

Reconfigurable antennas have emerged as a promising solution in wireless communication systems to adapt to dynamic environments and enhance system performance. Pattern reconfigurability plays a crucial role in improving antenna adaptability to spatially diverse multi-cluster channels, thus maximizing channel capacity. Existing works primarily address either the mode selection problem from a pre-designed finite pattern set which adjusts only beamwidth and scanning direction and thus can not offer optimal channel adaptation, or the mode design problem of computing continuously adjustable patterns under the assumation of an infinite pattern number but without considering the limit on the pattern number in real-world antennas. To address this gap, this paper proposes a practical design methodology that jointly accounts for the finite number of reconfigurable patterns and their precise optimization over diverse channel conditions. Specifically, channels are grouped based on user location distribution, and a joint optimization approach combining alternating optimization, auxiliary variables, and bisection is employed to design the optimal pattern set under the constraint of limited reconfigurable states. Simulation results demonstrate the effectiveness of the optimized patterns and show that the achieved capacity exhibits an approximately logarithmic relationship with the number of reconfigurable patterns, thereby providing a practical validation of existing theoretical analyses. This work bridges the gap between theoretical mode design and practical implementation by offering a concrete and implementable solution for designing a finite set of reconfigurable antenna patterns tailored to realistic system constraints.

This article presents an integrated dual-directional coupler chip operating from 300 MHz to 145 GHz, together with a dedicated packaging solution for seamless connection to 1.0-and 0.8-mm coaxial connectors, enabling direct application in next-generation ultrawideband vector network analyzers. The coupler, fabricated using micro metal additive manufacturing (M-MAM), allows high-order impedance-tapered design and a swiss-roll shaped folded topology for dense integration without significantly enlarging the chip area. To guarantee broadband impedance matching, the design combines a tailored multilayer process, time-domain optimization of reflection points, and specially engineered interconnection structures between the chip and coaxial connectors. In addition, the chip itself can also be configured with conventional ground-signal-ground (GSG) interfaces, enabling direct integration with MMIC chips; in terms of performance, with a 1.0-mm connector, the device achieves 120-GHz bandwidth, flat coupling of 11.5 +/- 0.37 dB, directivity >17 dB, and insertion loss below 3 dB. With a 0.8 mm connector, the working frequency extends to 145 GHz, achieving >14-dB directivity and <3.7-dB insertion loss. In addition, both couplers can operate down to 10 MHz, though the coupling will decrease at lower frequencies. To the best of our knowledge, this represents the widest bandwidth ever reported for a packaged dual-directional coupler, especially notable for its high directivity across nearly three decades of frequency range.

In this article, a guided-wave-inspired reconfigurable intelligent surface (RIS) with independent continuous amplitude and phase control ability is proposed. The designed RIS unit cell mainly consists of a top square patch, a middle metal ground, and a bottom reconfigurable attenuator-phase shifter cascade structure. By applying different bias voltages, the proposed RIS achieves a continuous amplitude modulation of 0.2-0.78 and a continuous phase modulation of 410 degrees at 4.9 GHz. As a validation, a RIS array consisting of 12 & times; 12 elements is fabricated and measured, generating dual beams with independent beam pointing and required power intensity allocation. Correspondingly, a RIS-assisted wireless communication system is constructed, and the performance of the proposed RIS is verified through image information transmission. In addition, a sub-bias network that can be flexibly extended according to the scale of the RIS array is designed to solve the problem of the increasing complexity of bias network arrangement caused by independent modulation of amplitude and phase. The proposed RIS has great application potential in RIS-assisted wireless communication systems, especially in scenarios where power intensities of the beams are allocated based on the data transmission rate requirements of different devices.

In this work, we achieve a method for the complete conversion of incident oblique waves into surface waves. By controlling the amplitudes of the coupled surface waves, both the direction and power distribution of the surface waves on the metasurface can be flexibly designed. First, using TE-polarized Gaussian waves incident at +40° and -40° as design examples, we demonstrate precise control over the direction and power of the coupled surface waves, thereby validating the proposed method for designing surface wave coupling metasurfaces under oblique incidence. Second, by using TE-polarized Gaussian waves incident at 0°, +20°, and +50°, we further demonstrate the capability of the metasurface to couple surface waves across a broad range of incidence angles. Finally, the impedance profile of the metasurface is implemented using subwavelength unit cells, and a physical prototype of the surface wave coupling metasurface is fabricated. Both numerical simulations and experimental measurements confirm the effectiveness of the design approach in simultaneously controlling the direction and power of coupled surface waves under oblique incidence.

This article presents a novel miniaturized multiport directional coupler designed for vector network analyzer frequency extension modules (VNAX modules). The proposed coupler is implemented using a cascaded configuration of three single-directional couplers, achieving high isolation performance and enabling the removal of isolators conventionally required in VNAX modules. Additionally, the device is realized using a broadband micro-coaxial structure, incorporating a frequency combining function (DC-70 GHz and 70-110 GHz). Specifically, the low-frequency signal propagates through a primary microcoaxial line, while the high-frequency signal is coupled into the main transmission path via a 10-12 dB coupler. Benefiting from the advantages of micro metal additive manufacturing (M-MAM) technology, the coupler is fabricated with a compact size (23 & times; 19 mm). Experimental results demonstrate that all functional ports of the coupler achieve a return loss better than 10 dB. The transmission loss remains below 1.6 dB within DC-70 GHz and between 11 and 14 dB within 70-110 GHz, exhibiting excellent agreement between simulations and measurements. Furthermore, the forward and reverse sampling ports show directivity better than 18 dB and typically better than 10 dB, respectively, over 70-110 GHz. To validate its practical application, a simplified VNAX module prototype employing the proposed coupler was assembled and tested. The results are compared with those of Ceyear's VNA and VNAX module, showing excellent performance.

In this work, a design method for the cylindrical metasurface cloak capable of simultaneously controlling beamwidth and beam direction is proposed. By precisely tailoring surface waves amplitude distribution along the cylindrical metasurface cloak, both the beamwidth ratio between the incident and outgoing waves and the direction of the outgoing wave can be designed as desired. First, taking a unity beamwidth ratio (1:1) as the design example, an incident Gaussian beam passes through the cylindrical metasurface cloak without reflection, and the outgoing wave maintains the same beamwidth as the incident one, thereby validating the effectiveness of the proposed surface wave coupling based cloak design. Second, to demonstrate beamwidth control capability, cases with beamwidth ratios of 2:1, 1:1.75, and 1:3.5 are successfully implemented. Subsequently, the cylindrical metasurface cloak design enabling directional control of the outgoing wave is presented, in which a horizontally incident Gaussian beam is deflected by the cloak at angles of +20°, –30°, and +50°, respectively. Finally, a cylindrical metasurface cloak design method that allows simultaneous control of both beamwidth and beam direction is established. The required impedance profile of the cylindrical metasurface cloak is realized using subwavelength structural units, and a practical cylindrical metasurface cloak prototype with dual control functionality is designed. Both numerical simulations and experimental measurements further confirm the accuracy of the proposed design method in achieving simultaneous and precise control over beamwidth and beam direction.

High-altitude electromagnetic pulse (HEMP) can couple into enclosures through apertures, cables, and other paths, posing a serious threat to internal electronic equipment. Traditional test methods struggle to accurately evaluate the real immunity of intra-enclosure electronic devices in HEMP environments. To address this, this article proposes a new statistical test method based on a reverberation chamber (RC). The field uniformity in the RC working volume under HEMP excitation is verified through experiments, and for a certain type of laptop, the statistical law of its failure probability varying with field strength is obtained. Results show that this method can effectively overcome the limitations of traditional directional tests and provide key probabilistic data support for HEMP protection design of intra-enclosure electronic equipment.

Array antennas are prominent candidates for millimeter-wave applications due to their indispensable highgain radiation. While the extreme wideband capability of conventional array antennas based on traditional feeding networks is advantageous for high-capacity networks, it constitutes a severe hardware overspill and cost limitation for emerging 5G Reduced Capability (RedCap) scenarios requiring lightweight terminals. For the fundamental suppression of this hardware redundancy, a design strategy that strategically relaxes wideband constraints is proposed to construct a lightweight $60-\text{GHz}$ slot array antenna. The structural simplification is achieved by exploiting the physical fact that a minor fractional bandwidth at the V-band natively provides sufficient absolute bandwidth, thereby strictly eliminating the necessity for complex feeding networks. The proposed antenna comprises a cascaded multi-height cavity topology, integrating a two-stage impedance-matching transition and a streamlined 8 -way power divider to meticulously regulate the electromagnetic boundaries for uniform aperture illumination. Benefiting from this severely simplified feed architecture, the final $8 \times 16$ array achieves a highly compact radiating aperture of $42.4 \times 35.2 \text{mm}^{2}$, demonstrating extensive application potential across costsensitive narrowband $\mathbf{5 G}$ scenarios. Simulated results demonstrate a solid $\mathbf{- 1 0} \mathbf{~ d B}$ impedance bandwidth from 57.8 GHz to 62.0 GHz, concurrently maintaining a stable realized gain ranging from 24.8 dBi to 27.1 dBi and a highly directive pencil beam.

We propose a wideband self-multipath decoupled interconnected slotted-patch antenna system that is capable of generating multiple decoupling nulls for the application of multiple-input multiple-output (MIMO) systems. By designing dual-port interconnected slotted-patch cavities, a total of four pairs of different self-decoupling paths are constructed using the common mode (CM) and differential mode (DM) of each cavity, which can produce counteraction effects at four different frequencies. The simulation results show that such dual-port interconnected slotted-patch antennas can achieve the isolation from 8 to over 20 dB within the 5--6 GHz wideband range when these two antennas operate in the same mode. Furthermore, this design can also be extended to the three- or four-port interconnected slotted-patch antennas with different rotation angles, realizing wideband decoupling performance between any arbitrary two ports. The proposed design possesses the advantages of wideband decoupling, miniaturization, and applicability to multiple antennas, presenting promising potential application value for high-integration wideband MIMO antenna systems.

work proposes a continuously reconfigurable linearly polarized antenna based on a cascaded phase-amplitude-polarization modulation mechanism, enabling continuous fullrange tuning of the linear-polarization (LP) axis from 0° to 180°. The proposed method first converts phase control into amplituderatio tuning through coherent vector synthesis and then realizes polarization manipulation by combining two orthogonal LP components with controllable amplitude ratios. A single control voltage is used throughout the tuning process, simplifying the biasing circuitry while enabling smooth polarization variation. As a result, the antenna radiates LP waves with arbitrary axis angles while maintaining realized gains above 6.7 dBi at 3.2 GHz. A 1×4 reconfigurable array is designed, fabricated, and measured, and the results confirm continuous polarization tuning over the full 0°-180° LP-axis range without significant gain degradation. A wireless image transmission experiment is further conducted, showing that the proposed antenna can effectively compensate for polarization mismatch and improve transmission quality under varying antenna orientations. These features make the proposed design attractive for unmanned aerial vehicle (UAV) terminals and dynamic Internet of Things (IoT) communication systems.

This article presents a high-efficiency dual-band balanced power amplifier (PA) that compactly integrates intrinsic diplexing and filtering functions, where the filtering function refers to the built-in interband isolation and undesired-band suppression generated by the path-interference mechanism of cascaded dual-band couplers. The proposed architecture combines dual-band couplers with PA stages, achieving interband isolation and diplexed power combining at two target frequencies of 1.4 and 2.5 GHz. This integration reduces the need for cascaded filters and diplexers typically used in conventional architectures, thereby reducing additional passive insertion loss. For validation, a prototype targeting 1.4 and 2.5 GHz was fabricated. At 1.4 GHz, the PA delivers a saturated output power ( $P_{\mathrm {sat}}$ ) of 43.6 dBm, a drain efficiency (DE) of 76.4%, and a saturated gain of 14.3 dB. At 2.5 GHz, it achieves a $P_{\mathrm {sat}}$ of 43.7 dBm, a DE of 72.8%, and a saturated gain of 12.6dB. The measured small-signal gains are 20.2 and 15.4 dB at the two bands, respectively, and the measured undesired-band suppression exceeds 23 and 22 dB for the 1.4- and 2.5-GHz input paths, respectively, while the interport isolation exceeds 30 dB near 1.9 GHz. Under a 10-MHz 5G NR signal with a peak-to-average power ratio (PAPR) of approximately 8.8 dB, the averaged ACLR values without digital predistortion (DPD) are −28.41/−27.52 dBc at 1.4/2.5 GHz. These results validate that the proposed architecture offers an effective solution for achieving high efficiency, high output power, and high integration in dual-band RF front-end modules.

The shared-aperture design of Sub-6 GHz and millimeterwave (mmW) antennas in mobile terminals has attracted increasing attention in recent years. Existing shared-aperture designs for spaceconstrained mobile terminals primarily aim to enable the independent coexistence of antennas operating at different frequency bands, while the shared structure itself rarely contributes to antenna performance improvement. Such improvement is particularly desirable for bandwidth-limited Sub-6 GHz antennas under ultra-small clearance. This work proposes a co-designed shared-aperture Sub-6 GHz/mmW antenna, in which the shared mmW antenna is intentionally designed to simultaneously function as a mmW radiator and a structure enabling boosted Sub-6 GHz radiation. To realize this concept, a long metal strip is segmented into five patches connected by high-impedance lines, thereby enabling boosted Sub-6 GHz radiation while maintaining mmW radiation. Three ground slots are introduced to suppress mutual coupling among the mmW elements. Experimental results show that, under an ultra-small clearance of only 0.6 mm (0.005λL), the measured −6-dB bandwidth of the Sub-6 GHz antenna is doubled from 100 MHz to 200 MHz at 2.6 GHz. Meanwhile, the mmW antenna covers 26.5–29.5 GHz, achieving a ±35° beam-scanning range and a peak gain of 10.8 dBi. The proposed concept demonstrates that the shared mmW radiator maintains its performance while enabling boosted Sub-6 GHz radiation, making it highly suitable for space-constrained mobile terminals.