Microwave and Optical Technology Letters最新文献

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.

This letter presents a low-profile, wideband, polarization-insensitive frequency selective rasorber (FSR) designed to reduce the radar cross section (RCS) of high-gain planar antenna arrays. The proposed structure consists of a lumped resistor-based lossy top layer and a lossless bottom layer, separated by an air gap. It achieves high absorptivity (> 90%) across 3.8–7.85 GHz and 9.67–13.4 GHz, while maintaining an in-band transmission at 8.5 GHz with an insertion loss of 0.9 dB. The fourfold symmetric and compact topology ensures polarization insensitivity and angular stability up to 50° incidence. The FSR is integrated with a planar microstrip patch antenna array, effectively reducing its out-of-band RCS under X-polarization and both in-band and out-of-band RCS under Y-polarization, without affecting in-band transmission. Both the standalone FSR and the integrated antenna system have been fabricated and measured, demonstrating up to 10 dB RCS reduction over a 111% fractional bandwidth under normal incidence.

In this paper, we present the design of a planar endfire circularly polarized (CP) antenna utilizing a periodic structure. The CP antenna is constructed on substrate integrated waveguide (SIW) that incorporates a periodic double-sided rectangular slot structure, culminating in a Vivaldi antenna at the end. The rectangular slot array generates vertically polarized (VP) electric field components for the far-field, while the Vivaldi antenna contributes horizontally polarized (HP) electric field components. By adjusting the distance between these two components, we achieve a phase difference of 90° between the two polarization components. This results in a planar endfire CP antenna that operates within the frequency range of 23.8 to 25.8 GHz, with an axial ratio of less than 3 dB. The antenna achieves a maximum gain of 11.73 dBi. The combination of high gain at small aperture translates to superior aperture utilization and easy edge/board integration, supporting compact endfire arrays, terminal-side AoA links and 24-GHz ISM sensing. Compared with recent planar endfire CP designs, the proposed radiator delivers comparable bandwidth but higher gain with smaller width, using a simple, low-loss, and manufacturing-friendly single-layer PCB implementation.

This study presents a combined theoretical and experimental exploration of a hybrid fiber-bulk master oscillator power amplifier (MOPA) laser operating in burst mode at a 10 kHz pulse repetition rate. By implementing an optimized pumping scheme, Gaussian-like gain profiles were achieved, ensuring uniform spatial beam characteristics throughout the MOPA amplification process. Full-energy beam quality assessment along orthogonal axes yielded measured values of M_x² = 2.8 and M_y² = 3.3, confirming favorable beam spatial characteristics. Additionally, temporal modulation of the burst envelope stabilized the pulse train output. The system demonstrated significant energy scaling, with the amplified pulse energy increasing from an initial 37.82 mJ to a maximum of 72.13 mJ, following a clear dependence on input pulse durations ranging in 20 ~ 80 ns.

In this study, we fabricated a U-band orthomode transducer (OMT) designed to measure the total radiated power (TRP) of an emission source and evaluated its performance through experiments and simulations. The proposed OMT achieved low loss and high isolation through a coupling slot and septum-based matching stub structure. To solve the problems of complicated fabrication and high cost that affect conventional multi-segmented OMTs, the proposed design adopts a simpler structure that allows easy and low-cost monolithic fabrication. In addition, we investigated the mechanical structure and manufacturability of the transducer using a cross-simulation analysis between CST and HFSS. The fabricated OMT was combined with a choke-ring antenna to detect electric fields in an OTA (over-the-air) test. The measured reflection loss, radiation pattern, and gain of the OMT and the antenna module indicated satisfactory performance in measuring TRP.