Microwave and Optical Technology Letters最新文献

This paper aims to present a novel methodology for noninvasive blood glucose monitoring. This method is based on monitoring the reflection coefficient of the proposed antenna-based sensor at three different bands simultaneously. This includes recording changes in the resonant frequency, magnitude, and phase. The above-mentioned parameters vary according to changes in blood conductivity and permittivity and consequently to blood glucose levels. A commercial FR4 substrate with compact dimensions of 30 × 40 × 1.6 mm³ is used to construct the proposed antenna, and all the simulations are conducted using 3D electromagnetic software. The proposed monopole is circular-shaped with an etched split ring resonator (SRR) to create multiband resonant frequencies. The proposed antenna measured the concentration of glucose level by using multiband resonant frequencies at 2.9, 4.3, and 6.5 GHz. The impedance bandwidth ≤ −10 dB is 1.038, 1.4, 2.02 GHz, respectively at each resonant frequency. To validate the operation of the proposed sensor, a container filled with samples representing different glucose concentrations is placed above the proposed sensor. To measure the blood glucose levels, a human finger phantom model is used with dimensions 15 × 12 × 10 mm³ in simulations. Moreover, glucose levels for four volunteers are compared in this paper before and after fasting using proposed sensors and a commercial glucometer. The proposed reflection-based microwave glucose sensing method exhibits an impressive sensitivity of 19.43 MHz/mg/dL.

In this letter, a compact differentially-fed end-fire filtenna is developed. The developed filtenna consists of three drivers, a director, a reflector, and a pair of U-shaped strips. Different from conventional Yagi antenna with a single driver, multiple drivers are employed to concurrently broaden the impedance bandwidth and facilitate the filtering response. To further improve the lower frequency selectivity, a pair of split rings is inserted between the driver and the director. And a radiation null at lower frequency is generated due to the out-of-phase surface currents on director and split rings. For verification, a prototype with a center frequency of 3.9 GHz is designed, fabricated, and measured. The measurement results have a good agreement with the simulation ones. The developed filtenna has a fractional impedance bandwidth of 14.4% (3.62–4.18 GHz), a peak realized gain of 5.8 dBi, a front-to-back ratio over 15 dB within the entire operational band. In addition, the filtenna also owns good filtering response with suppression levels higher than 16 and 25 dB for low- and high-stopband, respectively.

In this letter, a single-layer wideband filtenna with multiple controllable radiation nulls is presented. The developed filtenna has a very simple structure and is composed with a square substrate integrated waveguide (SIW) cavity, a square patch, and a pair of U-shaped slots. Notably, the filtenna possesses three radiation nulls that can be tuned by adjusting specific geometrical parameters. To achieve a wide bandwidth and better frequency selectivity, the TM₁₀ mode of the square patch is utilized to couple with the TE₂₁₀ mode of the square SIW cavity. And a radiation null at upper and lower edge of the passband can be simultaneously obtained because of the effective multipath coupling and the impact of TE₁₁₀ mode in SIW cavity. An extra in-band resonance and out-of-band radiation null are concurrently introduced by etching a pair of U-shaped slots at the metal ground plane so as to further expand the bandwidth and enhance the frequency selectivity. To validate the design method, a prototype of the filtenna operating at center frequency of 4.76 GHz was fabricated and measured. The measurement results show an impedance fractional bandwidth of 15.8% (4.38-5.13 GHz) and a peak realized gain of 6.1dBi.

In this paper, a single-layer differentially-Fed dual-polarized filtenna (DFDPF) with low cross-polarization is developed. The developed DFDPF consists of four shorted driven patches and four triangular parasitic patches. First, each single-feed driven patch resonates at its TM₁₀ mode (corresponding to the antiphase TM₂₀ mode of the two differentially-fed patches). Incorporating shorting pins on the driven patches leads to a lower radiation null. Then, the parasitic patches are embedded into the gap between the driven patches to introduce an extra in-band resonance operating in its TM_1/2,1/2 mode, along with an upper radiation null, while the footprint remains unenlarged. This improves operating bandwidth and roll-off rate on the upper passband edge. Finally, a pair of symbiotic open-ended l-shaped stubs are integrated into each driven patch to further enhance the suppression level of the upper stopband. The developed DFDPF was prototyped and measured for experimental verification. Experimental measurements validate the feasibility of the simulation results, demonstrating a wide –10 dB fractional impedance bandwidth of 19.5% and a peak realized gain of 6.6 dBi. In addition, the cross-polarization level is lower than –40 dB.

In this paper, a novel single-layer patch antenna is presented, designed to excite dual resonant modes for bandwidth expansion. By arranging these elements into an array, the mutual coupling between them is effectively suppressed by exploiting their inherent modes. This design strategy effectively suppresses mutual coupling in the antenna array without the need for additional decoupling structures. Instead, modifications in the physical placement of closely spaced antenna elements achieve high isolation. Within −10 dB of impedance bandwidth, an isolation greater than 25 dB is achieved by the array, with an antenna profile of 0.017 λ₀. Both simulation and experimental results demonstrate a strong correlation, affirming the design's effectiveness. The antenna array is capable of operating within the n78 band from 3.34 to 3.48 GHz, characterized by advantages such as high radiation efficiency, high isolation, and a low profile.

This work presents the effective steering of multi-harmonic beams of a time-modulated linear antenna array (TMLAA) for multi-channel communication. A classroom learning-inspired Teaching Learning Based Optimization (TLBO) is utilized for active duration optimization of the 16-element TMLAA for harmonic steering. The simulation study employing the optimization technique effectively steered the first two harmonic beams with enhanced radiated power and considerable Sidelobe level (SLL) below $��\; ��-�\; �20��\; �\mathrm{dB}��$. Further, for practical validation, the measurement of the fabricated prototype is presented for one scenario. Finally, the use of harmonic beams for the communication links is validated by measuring the bit error rate (BER) of the considered digitally modulated scheme.

This letter proposes a compact air-substrate single conductor endfire antenna, characterized by stable endfire radiation, high gain, high gain-to-length ratio and easy assembly. The proposed antenna is fed by air-substrate double-sided parallel strip lines (DSPSLs) in the TEM mode, ensuring stable endfire radiation pattern. Evolved from the periodic leaky-wave antenna design, it also achieves high gain. Moreever, the radiating elements can couple energy through two paths, achieving an almost uniform electric field distribution, which contributes to a high gain-to-length ratio. Notably, a single-conductor structure is achieved by terminating the short-circuited DSPSLs, which simplifies the assembly process and minimizes manufacturing complexity. Finally, the proposed compact single-conductor antenna is simulated, fabricated, and measured. The proposed endfire antenna features a compact size of 1.90λ₀ × 0.42λ₀ × 0.05λ₀ operating at the center frequency of 5.00 GHz, where λ₀ denotes the free-space wavelength. According to the measurement results, the antenna also achieves a high gain of 11.37 dBi and a high gain-to-length ratio of 7.21, exhibiting a wide 1-dB gain bandwidth of 4.00–5.30 GHz. These features make the antenna well-suited for diverse long-distance communication applications.

With the increasing digitalization of distribution network equipment (DNE), real-time update algorithms for digital twin (DT) models have become a research focus on the digitalization of DNE. However, traditional real-time update algorithms for DT models still have problems such as poor real-time, accuracy, robustness, and scalability. To better promote the development of digitalization of DNE, this article aimed to study the real-time update algorithm of DT models using the Internet of Things (IoT) and optical imaging technology, to achieve real-time updates of DT models of DNE. The article first described the problems existing in the traditional DT model of DNE. Then, IoT sensors and optical devices were used to collect data related to DNE; the Savitzky–Golay filtering algorithm was used to denoise the data. This article combined the IoT and optical imaging technology to construct a DT model; using the recursive least squares method again, key parameters and state parameters were extracted from the constructed DT mechanism model, achieving real-time updates of the DNE DT model. Finally, to verify the application effect of the IoT and optical imaging technology in real-time update algorithms for DT models of DNE, this article compared them with traditional parameter sensitivity analysis and state estimation. The research results showed that in the real-time and accuracy testing of test case 13, the algorithm used in this article had a time of 0.014 s and an accuracy of 93.2%. The parameter sensitivity analysis method had a time of 0.045 s and an accuracy of 80.4%. The state estimation method took 0.056 s and had an accuracy of 82.7%. In addition, the robustness and scalability of the real-time update algorithm for the DNE DT model using the method proposed in this article were significantly better than the other two traditional methods. The results showed that the real-time update algorithm of the DT model of DNE based on the IoT and optical imaging technology had better real-time performance, higher accuracy, and better robustness and scalability. This study highlights the significant impact of the IoT and optical imaging technology on the accuracy, robustness, and real-time performance of real-time update algorithms for DT models. This provides more solutions for real-time monitoring, prediction, and control of DNE.

Microstrip series-fed patch array antenna (SFPA) is increasingly prominent in millimeter-wave radar systems. Especially, SFPA with tapered amplitude using Dolph–Chebyshev, Taylor, and Binomial distribution has been developed to reduce a sidelobe level (SLL), which is critical to radar resolution. Even though reported designs of SFPA have achieved notable reductions in SLLs, the patch element and inter-element spacing optimized by simulation over the entire array design can't guarantee perfect in-phase radiation. Consequently, for nonuniform SFPA designs, achieving precise in-phase radiation necessitates a theoretical approach and a thorough phase analysis of each element. In this article, we present a noniterative design method to ensure in-phase feeding to each patch element by accurately compensating for the phase difference encountered in nonuniform SFPA. This approach begins with designing the electrical length of each patch element to be equal to 35 GHz. Subsequently, delay lines are then designed to provide in-phase feeding across the array while maintaining uniform spacing between elements. Consequently, we fabricated three 8-element SFPAs operating at 35 GHz and compared their performance, and the proposed design shows an SLL of –20.7 dB with a radiation angle of $��\; ��1�\; �.�\; �5^{\circ }��$.

The present study introduces a low-profile beam-steering metasurface lens antenna (MLA) that is excited by a defocused array antenna (DAA), eliminating the need for amplitude and phase excitation modulation. First, we modify an ultrathin Huygens' unit cell to provide greater angular stability, which is intended for use in beam-steering lens antennas. Subsequently, we analyze the effect of the focal–diameter ratio (F/D) on the beam-steering performance of the lens. Further, a one-dimensional (1D) MLA equipped with a DAA is modeled. Based on this model, we investigate the influence of DAA distance from the lens, DAA diameter, and F/D on radiation directivity and scanning capability. By adjusting the distance between the DAA and the lens, sub-arrays located in different regions of the DAA can be excited with uniform amplitude and phase, enabling dual-polarized single-beam scanning radiation. This excitation technique eliminates the need for amplitude and phase modulation networks, thereby reducing beam-steering costs and the complexity of the feed network. Finally, a 10$��\; ��{\lambda }_0�\; �\times ��$10$��\; ��{\lambda }_0��$ MLA prototype excited by a 52-unit dual-polarized DAA is simulated and fabricated. The simulation and measurement results demonstrate that the proposed MLA achieves a scanning range of ± 15°/± 16° in the E/H-plane at 10.3 GHz, with a gain fluctuation of less than 2.35/2.25 dB.