The continued growth of next-generation Internet-of-Things (IoT) networks is driving the demand for compact identification platforms capable of long-range operation and wide angular coverage. In this work, a planar metalens-enabled semi-passive millimeter-wave identification (mmID) system is presented for long-range localization while maintaining a compact form factor. The proposed architecture integrates a transmissive Huygens metasurface metalens, synthesized using compact Huygens unit cells, with a cross-polarized aperture-coupled stacked-patch antenna array to focus incident millimeter-wave (mmWave) energy onto the backscatter aperture while maintaining wide-angle operation. The fabricated mmID achieves a peak differential radar cross section (RCS) of −12.9dBsm with a −10-dB angular coverage of ±55° across all planes, corresponding to a solid-angle coverage of 2.68sr. The fabricated mmID further demonstrates frequency-modulated continuous wave (FMCW) ranging up to 85m with mean ranging errors below 4cm, phase-based localization with submillimeter precision at distances up to 20m, and simultaneous identification of multiple mmID devices operating at distinct modulation frequencies. Link-budget analysis projects kilometer-scale interrogation ranges under the maximum allowable 75-dBm equivalent isotropic radiated power (EIRP) for mmWave systems. By combining compact planar integration with wide-angle operation and long-range localization, the proposed metalens-enabled mmID provides a scalable platform for next-generation cyber–physical systems (CPSs), ambient IoT, and integrated sensing and communications (ISACs) applications.
This article presents a low-profile 27.5–31.5-GHz 256-element four-beam transmit (TX) phased array with a spatial third-order intermodulation distortion (IMD3) self-cancellation technique. By introducing phase offsets between reference and cancellation element groups arranged in a checkerboard layout, spatially directed IMD3 products can be suppressed through destructive far-field interference without additional hardware. The 256-element multibeam phased array (MBPA) is constructed from four seamlessly tiled 64-element subarrays, each integrating 16 Ka-band 65-nm CMOS four-beam TX beamformer chips. A wideband dual-polarized (DP) stacked patch antenna array with decoupling structures and a high-isolation onboard four-beam power-dividing network enables four independent polarization (Pol)-reconfigurable beams. The MBPA achieves >39.2-dB measured active inter-beam isolation, ±60° grating-lobe-free scanning, >22-dB cross-Pol discrimination, sub-1-dB axial ratio (AR), and 67.5-dBm peak effective isotropic radiated power (EIRP) at saturation. The proposed MBPA achieves the state-of-the-art number of simultaneously reconfigurable fully connected beams among millimeter-wave (mmWave) active TX phased arrays. Experimental results demonstrate >20-dB IMD3 suppression, yielding >44-dB spatial IMD3 rejection ratio (SIMR) across both sidebands and both Pols while requiring only ~1.25-dB fundamental combining loss, supporting a 2H+ 2V four-beam linearized operating mode and offering a TX-side linearization approach for MBPA systems.
Recent advancements in hybrid quantum-classical algorithms (HQAs) have demonstrated significant potential for solving large-scale electromagnetic (EM) problems based on the finite element method (FEM). However, existing quantum EM solvers are fundamentally restricted to discrete, point-by-point frequency evaluations. For broadband microwave component design, executing iterative quantum circuit optimizations at each sampled frequency imposes a substantial computational overhead, limiting the practical applicability of broadband quantum EM simulation. To overcome this limitation, we propose a hybrid quantum-classical Krylov subspace projection (HQKSP) method for the fast frequency sweep of FEM-based EM simulations. Instead of repetitive quantum evaluations across the entire frequency band, the proposed method constructs a reduced-order model by generating a set of basis vectors that span a Krylov subspace at a single expansion frequency. To mitigate the quantum circuit depth limitations associated with strict second-order moment matching, we introduce a hardware-efficient recursive strategy to sequentially generate the basis vectors, bypassing the need for deep linear combinations of unitaries (LCUs). A quantum postprocessing mechanism is then developed to track and compensate for the accumulated relative phase offsets, restoring the phase coherence of the subspace. Subsequently, a direct quantum Galerkin projection is employed to compress the massive FEM system matrices into a low-dimensional space. Because the reduced matrix elements are evaluated only once at the expansion point, the quantum projection overhead is independent of the frequency sweep density. Therefore, the proposed HQKSP method enables the accurate extraction of complex-valued S-parameters while offering a potential reduction in frequency-dependent quantum computational overhead for broadband EM simulations. Numerical experiments on microwave components demonstrate that the proposed HQKSP method achieves the fast frequency sweep via quantum evaluations and classical postprocessing, maintaining close agreement with classical full-wave simulations.
In dynamic microwave wireless power transfer (MWPT) systems, maintaining beam alignment with a moving target generally requires a complex and costly phased-array front end. To realize a low-cost and compact transmitter while reducing system complexity, this article presents a compact substrate-integrated suspended line (SISL)-based multibeam antenna array. A miniaturized coupler is first developed by exploiting the dual-layer equipotential routing capability of the SISL structure and introducing stepped-impedance stubs, significantly reducing the circuit size while maintaining good performance. By employing a crossover-free topology together with compact phase shifters, the proposed $4\times 4$ Butler matrix achieves low insertion loss and excellent amplitude-phase consistency. The proposed Butler matrix occupies only $0.96~\lambda ^{2}_{0}$ , while maintaining measured amplitude and phase imbalances within ±0.18dB and ±2.72°, respectively. Furthermore, a vertically integrated multibeam antenna system is realized through multilayer PCB stacking, enabling high integration and stable multibeam radiation characteristics. To validate the proposed architecture for dynamic MWPT applications, a switched-beam wireless power transfer (WPT) prototype incorporating a PIN-diode-based RF switching network is implemented. Experimental results demonstrate stable WPT to the moving target with wide-angle beam coverage from −56° to 58°.
This article presents a novel topological structure and design methodology for a circular TE01 mode waveguide bend used in high-power transmission lines. The proposed design substantially improves both bandwidth and compactness through two innovative topological features. First, a multiaperture sidewall coupling topology is introduced to split the TE01 mode into multiple rectangular TE10 intermediate modes, with the azimuthal symmetry of the multiaperture structure effectively suppressing parasitic modes and broadening the operating bandwidth. Second, a multibranch folded rectangular waveguide topology incorporating a dedicated phase compensation scheme is implemented to significantly enhance structural compactness while maintaining broadband transmission efficiency. The mode conversion mechanism, design methodology, numerical simulations, and experimental measurements of an X-band prototype are described. The simulated and measured results are in good agreement. Over the measured frequency range of 7.9–12.2 GHz, corresponding to a relative bandwidth of 42.8%, the waveguide bend exhibits a reflection coefficient lower than −15 dB, an average transmission efficiency exceeding 94.6%, and an output mode purity higher than 97.2%. The transverse distance between the input and output ports is only $6.3\lambda _{0}$ ( $\lambda _{0}$ is the free-space wavelength at 10 GHz). Moreover, the proposed topology supports modular design for arbitrary bending angles and demonstrates clear advantages in broadband performance, high conversion efficiency, and structural compactness.
