Microwave and Optical Technology Letters最新文献

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.

A dual-polarized filtering antenna with radiation nulls based on crossed-dipole is proposed in this letter. The antenna consists of three parts, including two baluns, a ground plane, and a metal wall. Two dipole arms are directly integrated into the balun structure to ensure balanced current distribution. By loading two bent λ/4 open-circuited stubs along the microstrip feedline of the balun, filtering performance is obtained as two radiation nulls are generated at the lower/upper edges of the operating band. Additionally, with the introduction of metallic wall, the in-band gain stability is enhanced while the front-to-back ratio (FBR) is improved. For demonstration, the proposed antenna is fabricated and measured. The simulated and measured results demonstrate that better than 15 dB out-of-band suppression levels are realized. Moreover, the proposed antenna achieves −10 dB fractional impedance bandwidths of 27.8% and an average in-band realized gain of 7.5 dB, making the proposed antenna a promising solution for dual-polarized filtering antenna.

The article proposes a design of a rectangular microcoaxial line (RμCL) to a microstrip line (ML) transition structure for ultrawide mmW (millimeter-wave) chip integration. The proposed transition structure is designed to operate effectively in the frequency range from DC to 67 GHz, ensuring good chip interoperability. To validate the design methodology, the transition structure was tested using the back-to-back model and experimental analysis. The results demonstrate that the transition structure exhibits a significant return loss exceeding 15.5 dB and an insertion loss below 1.4 dB within the frequency range of DC–67 GHz. With this transition, the feasibility of chip integration for UWB microcoaxial millimeter wave chips has been established.

With the deep penetration of Wireless Body Area Network (WBAN) in scenarios such as medical monitoring and sports health, there is a growing demand for wearable patch antennas that offer enhanced directional performance and flexibility. This paper presents a novel pattern-reconfigurable planar dipole patch antenna designed for the 5 G N79 band (4.4–5 GHz). The proposed design incorporates a reconfigurable balun structure and four parasitic metal strips loaded with PIN diodes for beam control. By switching the diodes ON or OFF, the parasitic strips can function either as reflectors or directors, enabling four-directional beam reconfiguration. In free space, when the antenna operates in State 1 or State 4, it attains an impedance bandwidth of 174 MHz (4.389–4.563 GHz), and when operating in State 2 or State 3, it reaches an impedance bandwidth of 149 MHz (4.363–4.512 GHz). The antenna features a compact size of 1.02 × 1.02 × 0.22 λ₀³ and achieves the measured peak gain of 5.084 and 4.463 dBi in State 1 and State 2, respectively. The measurement results are in good agreement with the simulation results, and both the S₁₁ parameters and the radiation patterns meet the expected performance. In addition, when the antenna is placed close to the human body, the low Specific Absorption Rate (SAR) values demonstrate its safety for wearable applications.

In this paper, a two-order high aperture efficiency filtering metasurface antenna (MSA) based on printed ridge gap waveguide (PRGW) technology is investigated. The classical filtering antenna synthesis approach is employed to facilitate the seamless integration of PRGW resonators and MSAs. To further improve the gain roll-off rate, size-reduced mushroom-shaped unit cells are strategically integrated into the PRGW feeding network. Since it does not occupy extra space, the proposed MSA element possesses a compact size of 0.38λ₀ × 0.38λ₀ (λ₀ is the free space wavelength at the center frequency). To validate the proposed design concept, a 1 × 4 filtering MSA array is designed. Measurement results show that the prototype exhibits an impedance bandwidth of 2.25% for |S₁₁ | < −10 dB, an average gain of 7.08 dBi across the passband, and a maximum aperture efficiency of up to 58%. Furthermore, gain roll-off exceeding 16.2 dB/GHz can be achieved in both the upper and lower stopbands.

The design of a novel millimeter-wave low-profile low-cost waveguide matched load based on multilayer substrates and water medium is presented in this paper. Different from the traditional metal waveguide matched loads based on resistive material, the proposed design relies on the high loss characteristics of the water medium for millimeter waves to achieve excellent matching performance. In addition, the multilayer substrates integrated waveguide is utilized in the presented waveguide matched load, characterized by low-profile and planar features, which contribute to its compactness and structural stability. The presented circuit is fabricated by using conventional PCB processing technology, with the size of 0.2λ_g × 0.2λ_g × 0.006λ_g. In the frequency range of 29.7–34.5 GHz, the measured S11 of the presented circuit is less than −20 dB, and the fractional bandwidth reaches 15%. The results effectively validate the practical viability of the proposed design, indicating that the novel waveguide matched load based on water medium can be a promising alternative to traditional design.