Microwave and Optical Technology Letters最新文献

This paper presents a compact ultra-wideband (UWB) power divider that uses microstrip lines to achieve stable performance over a wide frequency range. The circuit is designed for wideband operation as well as being easily fabricated using standard FR-4 substrate. Simulation results show that a bandwidth of 5.38 GHz is achieved in the frequency range of 1.6–7.0 GHz and the minimum S₁₁ value is –31.78 dB. The measured transmission coefficients (S₂₁ and S₃₁) are in close agreement with the simulated data, both around –3.56 dB, confirming consistent power splitting. The proposed design has been optimized through a detailed parametric study and demonstrates improved isolation and reduced reflection while maintaining simple rectangular geometry. Compared with previous multilayer or high-cost laminate designs, the proposed FR-4-based divider achieves 125% fractional bandwidth and high fabrication tolerance while maintaining a simple geometry suitable for wide-band microwave and communication systems.

This work proposes an improved shooting and bouncing ray (SBR) method for calculating the near-field scattering of electrically large objects. In near-field calculations, there is a divergence problem in the ray tube of the SBR method, which exacerbates the splitting of the ray tube. The traditional near-field SBR method suffers from accuracy loss, as the problem of ray tubes aperture divergence is only solved in first-order scattering calculations and is ignored in higher-order scattering calculations. This problem can be solved by dividing the ray tubes into denser ones, but this will reduce computational efficiency of the SBR method. This work proposes an adaptive tube subdivision method to control the ray tube aperture size and ensure ray tracing accuracy, which can effectively solve the problem of computational accuracy loss caused by tube divergence in near-field calculations, while taking into account the computational efficiency. Several examples are designed to verify the effectiveness of the method.

This paper presents a comprehensive study on the gain enhancement and higher Isolation of a 28 GHz MIMO antenna system for 5 G communications using Frequency Selective Surfaces (FSS). The antenna under study is designed with dimensions of 2.86λ × 2.86λ × 0.047λ; the ground patches have a dimension of 7.6 × 11 mm², the substrate is a Rogers RT885 (εr = 2.2, height = 0.51 mm), and operating at 28 GHz. A 4-element MIMO antenna array is formed by orthogonally placed elements in order to optimise spatial diversity. To improve isolation between the antenna elements, a mutual coupling reduction technique is employed. Furthermore, a 36-element FSS array is strategically placed above the MIMO antenna to significantly boost the gain. The initial gain performance without the FSS is 4.2 dBi at 28 GHz, by placing the FSS surface 7 mm above the MIMO antenna, this increases the gain to 8.4 dBi, resulting in a gain enhancement of approximately 3.6 dBi. Simulation results, obtained using CST Microwave Studio, demonstrate notable improvements in the antenna gain. The integration of FSS proved to be an effective solution for meeting the stringent performance requirements of 5 G communication systems, particularly in high-frequency mmWave applications. The present work aims to enhance gain, get high efficiency, improve the isolation between the ports, good value of ECC.

In this letter, a filtering antipodal Vivaldi antenna (AVA) integrating spoof surface plasmon polaritons (SSPPs) and directors, featuring controllable passband characteristics and high gain, is proposed. In the antenna configuration, a set of slots etched along the outer edges of the radiation arms improves the low-frequency gain, while antenna-terminal-loaded semi-annular directors further enhance the overall gain. The filtering characteristics can be conveniently tuned by adjusting the dimensions of the branched circular metallic patch and the SSPPs structure. A prototype operating from 7.44 to 11.76 GHz was fabricated and experimentally characterized to validate the design. Measurement results demonstrate an impedance bandwidth of 45%, stable in-band gain with a peak value of 12.14 dBi, and inherent advantages of wide bandwidth and low profile. Compared with conventional AVAs, the proposed design exhibits improved radiation characteristics, achieving both higher gain and superior filtering performance.

In this paper, a class of bandpass filters (BPFs) with symmetric ultra-wideband reflectionless characteristics is presented. Specifically, two types of reflectionless BPFs are proposed by integrating multiple bandstop sections with embedded absorption resistors. To further enhance port reflection suppression, two distinct methods of introducing additional reflection zeros (RZs) are implemented. To practical verification, prototype circuits of five-stage reflectionless BPFs with a center frequency of 2 GHz were designed, simulated, and fabricated. Measurement results demonstrate that the two BPF prototypes achieve fractional bandwidths of 32.9% and 29.0%, respectively, with over 10 dB reflection suppression across frequency ranges of 0–5.59f₀ and 0–5.62f₀. The experimental results validate the effectiveness of the proposed approach in achieving ultra-wideband reflectionless performance.

In response to the urgent demand for broadband, high-gain dual-polarization antennas in 5G/6G mobile communication systems, this paper proposes a novel dual-polarization base station antenna based on a double-layer uniform metasurface and spoof surface plasmon polariton (SSPP) feeding. This design innovatively combines cross-dipole radiators with a dual-layer metasurface structure, optimizing radiation characteristics through the upper metasurface while achieving broadband impedance matching via the lower metasurface. Additionally, the SSPP feeding structure effectively suppresses surface wave losses, enhancing radiation efficiency. Test results show that the antenna has a reflection coefficient below −10 dB (relative bandwidth of 62.0%) in the 2.30–4.37 GHz frequency band, with a maximum gain of 13.25 dBi and port isolation exceeding 20 dB. Compared to traditional designs, this antenna achieves ultra-wideband characteristics and high gain performance at a low-profile height of $��\; ��0.20�\; �{\lambda }_0��$ (wavelength at the center frequency). Parametric analysis has validated the critical role of metasurface units in regulating multiple resonance points, providing new insights for the integrated design of millimeter-wave base station antennas.

This letter proposes a compact high-gain filtering antenna array with enhanced out-of-band suppression. The design integrates a rectangular radiation patch with two groups of parasitic patches, fed by a bifurcated feed line through dual slots in the ground plane. Substrate 2 is changed into a hollowed-out ring-shaped substrate, so as to realize the structure of the built-in air layer and improve the impedance matching and gain of the antenna. The feeding structure creates a radiation null at the lower band edge, achieving low-frequency selectivity. These elements generated three resonance points, expanding the impedance bandwidth. Dual radiation nulls are generated at the high-band edge through slotting on the radiation patch and the coupling between the radiation patch and the parasitic patch, enhancing out-of-band suppression in the high-frequency band. A fabricated 2 × 2 filtering antenna array prototype demonstrates a 15.81% impedance bandwidth (22.31–26.14 GHz), peak realized gain of 14.32 dBi, and average total efficiency exceeding 88%. The configuration offers enhanced out-of-band suppression while maintaining structural simplicity.

In this paper, a magneto-electric dipole (MED) filtering antenna with a novel filter feed network is proposed. The proposed antenna is based on the low-temperature cofired ceramic (LTCC) process. The MED antenna has an intrinsic radiation null, and a mathematical model of the magneto-electric dipole is presented to elucidate its working mechanism. An innovative shared-edge C-shaped slot structure has been implemented on the ground plane to form a novel filter feed network. The configuration employs two adjacent C-shaped slots of different dimensions sharing a common edge, achieving significant space reduction. At certain specific frequencies, the energy concentrates in the shared-edge C-shaped slots and does not couple to the radiation patches, causing radiation nulls. To analyze this principle, equivalent circuits of the novel filter feed network are provided. The proposed antenna has a total of four controllable radiation nulls with excellent out-of-band rejection. For verification, a MED filtering antenna is designed, fabricated, and experimentally validated. The measurement results indicate that the antenna has an impedance bandwidth of 21.7% (11.9–14.8 GHz), an average gain of 5.0 dBi in the passband, and the out-of-band suppression level is better than 20 dB.