Microwave and Optical Technology Letters最新文献

A novel filtering antenna based on spoof surface plasmon polaritons (SSPPs) is presented. The antenna has high suppression performance and tunable radiation nulls. The proposed antenna mainly consists of four parts, a metal ground, an SSPP-based transmission line etched with slots, two driving elements on the upper and bottom surfaces, and three parasitic elements on the upper surface. By using the proposed SSPP-based transmission line, good out-of-band suppression performance is achieved. Moreover, the out-of-band resonances are suppressed by etching slots in the SSPP structure. Besides, the radiation nulls of the antenna can be tuned by adjusting the key geometrical dimensions, which would be useful to fit different interference. The measured operating band is 2.130–2.606 GHz (20.1% at f₀ = 2.368 GHz), the in-band average gain of the proposed antenna is 8.89 dBi with the peak realized gain of 10.55 dBi. The upper out-of-band suppression level is larger than 23.708 dB over 3.2–7.4 GHz band, while the gain response decreases rapidly from the maximum value (10.55 dBi at f = 2.52 GHz) to the minimum value (−67.315 dBi at f = 3.4 GHz).

We propose a novel and robust bias control method for Mach–Zehnder modulators that enables precise stabilization using low-amplitude pilot tones without requiring the detection of second- or higher-order harmonics. The technique relies on the ratio of the partial derivative of the direct current component to that of the first-order pilot tone with respect to the bias voltage, serving as a high-sensitivity feedback signal. Simulation and experimental results verify that the method significantly lowers the required pilot tone power, mitigates intermodulation distortion, and improves system linearity. Furthermore, it ensures stable and accurate bias control even under optical power fluctuations, making it particularly well-suited for microwave photonic links that demand high signal-to-noise ratios.

This paper innovatively proposes a phase-tunable phase shifter with filtering functionality, which utilizes the concept of transversal signal-interaction. It further achieves the extension of phase adjustment by cascading with switch-type phase shifters. The structure is analyzed using even- and odd-mode analysis and validated through full-wave simulations and measurements. Experimental results demonstrate 373° phase shift at 1.75 GHz with 7.4% bandwidth, ± 10.3° phase error, and 4.9 dB maximum insertion loss. The design achieves precise phase control in a miniaturized layout suitable for 5G beamforming systems.

This letter presents a 2–17 GHz low-noise amplifier (LNA) Monolithic Microwave Integrated Circuit (MMIC) with a temperature compensation circuit, implemented in a GaAs depletion-mode (D-mode) process using a single power supply. A temperature-compensated bias circuit using a source diode is introduced, followed by a negative feedback circuit to extend the bandwidth. The design employs a single power supply for enhanced practicality. Measured results show a gain exceeding 14 dB, a noise figure (NF) below 3 dB, and input/output return losses greater than 10 dB. The gain variation remains within ±0.001524 dB/°C from −55°C to +125°C. This LNA exhibits ultra-wideband performance and excellent gain stability across a wide temperature range.

In this letter, an ultra-thin and broadband transmissive linear-to-circular polarization converter (LTCPC) is presented. This LTCPC consists of a single substrate with symmetrical metallic patterns on its surface, composed of split rings and an internally orthogonal crossed dipole. By orthogonal decomposition of linear polarized (LP) waves from different directions, this converter can realize circularly polarized (CP) transmission, and the type of CP transmitted wave can be switched by changing the incident LP direction. The proposed converter achieves a 3 dB axial ratio (AR) bandwidth of 32% (26.5–36.6 GHz) and maintains stable AR performance under oblique incidence angles up to $��\; ��4�\; �0^{\circ }��$. It features a low profile with a compact volume of 0.016$��\; ��{\lambda }_0^3��$, where $��\; ��{\lambda }_0��$ is the wavelength of the center frequency. After full wave simulation, a prototype of $��\; ��16�\; �\times �\; �16��$ cells was fabricated and tested. A comparison shows that the tested and simulated results are almost the same. With its good polarization conversion performance and ultra-thin profile, the proposed LTCPC can find wide applications in Ka-band satellite communications.

As demand for high-speed data increases, 5G has become the leading technology in telecommunications. A key aspect of creating high-capacity, low-latency systems is the design of antennas. This paper introduces an antenna crafted from innovative pure polytetrafluoroethylene (P-PTFE) material with a dielectric constant (ε_r) of 2.1 and a loss tangent (δ) of 0.0002, recognized for its flexibility and resistance to heat and chemicals. This material offers several advantages for the proposed antenna, including a compact size of 18 × 22 × 1.6 mm³, making it suitable for wearable applications, and the ability to operate over a wide frequency range from 2.7 GHz to 100 GHz. Two models for antenna design were developed: one was simulated using Computer Simulation Technology (CST) Studio, and the other was based on actual manufacturing. Discussions addressed all parameters to evaluate performance. The antenna achieves a wide bandwidth of 81.979 GHz, with the S-parameter remaining below −10 dB from 2.7 to 100 GHz. Additionally, this antenna offers a gain range of 3–11.60 dBi and exhibits an overall efficiency of 70%–92% across all frequency bands. These attributes make the antenna fabricated from innovative P-PTFE material well-suited for a wide range of 5G and future 6G applications.

This paper presents a low-cost, wideband, high-gain circularly polarized horn antenna system realized through additive manufacturing. The proposed design integrates a three dimensional-printed pyramidal horn antenna with a phase-graded metasurface (PGM) lens and a dielectric polarizer (DP). The PGM lens, composed of cuboidal unit elements, is engineered based on near-field phase transformation principles to enhance directivity and gain. The DP, featuring an air-cavity slab configuration, enables effective linear-to-circular polarization conversion over a broad frequency range of 25.4–38 GHz. Circular polarization is achieved through axial rotation (ϕ = ±45°) of the DP at the horn aperture, generating left-hand circular polarization and right-hand circular polarization, respectively. The antenna demonstrates a 3 dB axial ratio bandwidth of 35.66% (26–37.4 GHz) and a 1 dB gain bandwidth of 42.13% (25.36–38 GHz). A prototype has been fabricated using additive manufacturing techniques, and measured results exhibit close agreement with simulations. The proposed antenna system offers a compact, cost-effective, and high-performance solution suitable for synthetic aperture radar applications in weather monitoring.

This paper proposes a 5G MIMO wideband four-coupled-feed square-ring patch antenna system specifically designed for access point applications in next-generation wireless communication networks. The system features a compact and low-profile form factor, with an overall footprint of 50 × 50 mm² and a height of 10 mm, making it well-suited for integration into space-constrained devices. The antenna array is built on a 35 × 35 mm² FR4 substrate with a thickness of 0.8 mm, corresponding to approximately 0.484 × 0.484 λ at the center frequency of 4.15 GHz. Each of the four antenna elements comprises a rectangular metal ring structure with dimensions of 19 × 13 mm² and is symmetrically arranged in a rotational configuration to ensure polarization orthogonality. This design approach effectively enhances port isolation, maintaining port isolation above 10 dB, without the need for additional decoupling structures. The antenna system operates efficiently across a wide frequency band from 3.3 GHz to 5.0 GHz, covering the sub-6 GHz spectrum allocated for 5G communication. Key MIMO performance indicators, including the envelope correlation coefficient (ECC) and channel capacity loss (CCL), are maintained below 0.09 and 0.2, respectively, across the entire band, signifying low mutual coupling.

This paper presents a novel ultra-wideband (UWB) miniature antenna operating from 0.25 to 14.9 GHz with VSWR < 2.5. Wideband coverage is achieved by integrating a compact dipole antenna with a series-fed log-periodic dipole array (LPDA). The dual-module design utilizes an equivalent tightly coupled dipole for low-band radiation and the LPDA for high-band operation. Replacing the terminal LPDA dipole with a compact dipole significantly enhances miniaturization. Measured and simulated results show a 59.6:1 impedance bandwidth, compact dimensions of 0.16λ₀ × 0.34λ₀ × 0.16λ₀, and gain of 3.22–8.57 dBi. This study successfully integrates a compact dipole within an LPDA, The proposed antenna is well-suited for applications such as ranging, side-looking radar, and microwave imaging.