查看更多>>摘要：In this letter, a low-profile spin-decoupled folded reflectarray antenna (SDFRA) with dual-circularly polarized beam control is proposed, which can realize spin angular momentum (SAM) decoupling. Impressively, the substrate used in this antenna is reduced to three layers. The proposed SDFRA consists of a receiver-transmitter metasurface (RTMS), a polarization conversion reflection metasurface (PCRM), and a magneto-electric (ME) dipole antenna. Specifically, the RTMS can reflect the x-polarized waves and transmit its orthogonal polarization waves. Meanwhile, the transmitted waves can be decomposed into left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) waves. To confirm the concept, a prototype is fabricated and measured. The results indicate that the 3 dB gain bandwidth of the LHCP beam and the RHCP beam are 20.89% and 21.3%, respectively. The maximum realized gain of the LHCP and RHCP beams are 20.55 dBic and 20.52 dBic, corresponding to aperture efficiencies of 19.06% and 19.19%. The experimental results are in good agreement with the simulated results. With the advantages of broadband, low profile, and low cost, this antenna provides an effective solution for single-band dual-circularly polarized beam control.
查看更多>>摘要：The purpose of path loss modeling is to predict signal fading in various environments, which is crucial for the planning, deployment, and optimization of mobile networks. Existing path loss prediction methods based on machine learning have poor generalization at sparse measurement areas, and most require 3-D information about the environment or specific parameters of the base station. We propose Meta-PL, a path loss prediction model based on meta-learning, to infer signal strength at sparse measurement areas. The method divides the research area into multiple grids of uniform size, each grid as a task of meta-learning. Experimental results show that in a 100 × 100 area with 10 measurement data, the root-mean-square error (RMSE) and mean absolute error (MAE) can achieve optimal values of 2.63 dB and 2.01 dB, respectively. Furthermore, Meta-PL relies only on open street maps and base station locations and does not need other information about the base station or 3-D environmental information.
查看更多>>摘要：This letter proposes a wideband (20 GHz) transparent metasurface for mobile phone glass covers. This metasurface enhances 5G/6G millimeter-wave (mm-wave) transmission and mitigates the negative impact of glass on the mm-wave antenna module located beneath the glass rear cover. To achieve high transparency, a 600 nm thick aluminum hexagonal-shaped grid is employed. To achieve wide bandpass behavior and improve angular robustness without increasing thickness or adding additional substrates, a second-order filter has been designed. Simulations and measurements have been performed to verify the model. The 3-D radiation patterns confirm that the metasurface can reduce the effects of glass on the top of the antenna and provide a single beam broadside radiation pattern.
查看更多>>摘要：The use of planar near-field measurements to determine antenna gain is widespread. However, the accuracy of the results is strongly dependent on the size of the sampling area, especially when working in limited test spaces, which affects the precision of the gain measurements. To overcome this limitation, our method uses a virtual array source with adjusted amplitude and phase distributions to extend the sampling field, allowing accurate gain measurements within a small planar near-field and increasing test efficiency. Notably, it remains valid even when the maximum radiation direction is not aligned with the center of the sample plane. Both numerical simulations and experimental data confirm the effectiveness and feasibility of our proposed method, which increases test efficiency and reduces the required sampling area.
查看更多>>摘要：A W-band active electrical scanning phased array antenna is proposed by employing a metallic open-ended waveguide as a radiation element with integrated fan-out work for high radiation efficiency in this letter. By mounting four metallic walls on the aperture of the open-ended waveguide, the scanning active voltage standing-wave ratio (VSWR) can be improved. Additionally, a waveguide-based fan-out network is designed to enlarge the spacing between the open-ended waveguide antenna elements and integrate the T/R module into the waveguide array. The simulated results demonstrate that the proposed array achieves VSWR<2 from 86.4 GHz to 110 GHz with an impedance bandwidth of 23.6% within ±30° scanning in the E-plane and H-plane. A high radiation efficiency of above 87% is obtained at the W band. An 8 × 8 prototype is fabricated and measured. Good agreement is achieved between the simulated and measured results.
查看更多>>摘要：A more accurate shooting and bouncing ray method (SBR) based on curvature wavefront ray tracing is proposed for radar cross section (RCS) simulation of triangular meshed curved targets. The key idea is to approximate the ray tube of each triangle using the wavefront of its center ray, thus accurately characterizing the divergence factor during multiple reflections. Surface fitting and differential geometry techniques are used to reconstruct the curvature of the triangular mesh and calculate the wavefront variations of the ray tube during multiple reflections, while also accounting for thin-coated targets. Moreover, a curvature wavefront-based ray tracing method is developed, significantly enhancing the sampling accuracy. The accuracy of the proposed SBR is validated through comparison with the FEKO multilevel fast multipole method (FEKO-MLFMM), and the simulation time consumption is acceptable.
查看更多>>摘要：In response to the insufficient isolation of microstrip triplexers, this work presents a design method for a tri-band antenna integrated with a passive triplexer. Based on the analytic resonant characteristics of stepped impedance resonators (SIRs), the combination of SIR and transmission lines is used to meet the impedance conditions required by the common junction of the triplexer. It has a simple structure, straightforward design equations, and high layout flexibility. A shorting pin is used to directly cascade the triplexer with a tri-band antenna, realizing the single printed circuit board (PCB) integration of the triplexer, antenna element, and feeding structure. Focusing on the application requirements of BeiDou communication and navigation systems, a circularly polarized triplexer antenna with isolation greater than 52 dB between the transmitting and receiving ports is proposed.
查看更多>>摘要：A miniaturized dual-polarized patch antenna with high isolation and low cross polarization is presented in this letter. The antenna is printed on two substrate layers with three metallic layers. The square patch on the top is fed orthogonality by two probes for dual-polarized radiation with TM10 and TM01 modes. A thin metallic strip is cut off from every radiation edge and loaded by a via row. The electromagnetic waves of the two modes are radiated from the gaps between metallic strips and the square patch and become more concentrated and symmetric, which reduces the cross-polarization and improves the port isolation. By introducing the interdigital structure in the radiation slots, the patch is miniaturized with an electrical size of 0.23$\lambda _{0}$ × 0.23$\lambda _{0}$ × 0.07$\lambda _{0}$ ($\lambda _{0}$ is the free-space wavelength at center frequency), which is about 71% area of a conventional square patch antenna. The measured results show that the isolation is greater than 46 dB, and the cross-polarization is less than −42 dB at the operating frequency of 5.8 GHz. This antenna also has the function of harmonic suppression. The good advantages and miniaturized size make the proposed antenna a preferable choice for various wireless communication systems.
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