Microwave and Optical Technology Letters最新文献

A device comprised of gold patch antennas with Bi₂Te₃ and Sb₂Te₃ thermoelectric lines has been fabricated using optical lithography and characterized using a vector network analyzer (VNA) to analyze the thermoelectric voltage as a function of electromagnetic power. Simulation results show that this device has a resonance at 10 GHz. The calculated bandwidth for this dual microstrip patch is 7 GHz which is an improvement over non-thermoelectric rectangular microstrip patches which are known to be narrow-band antennas. Experimental results where the source antenna power was varied from 0 to 10 mW (−20 dB) show that the resulting thermoelectric voltage measured at the thermoelectric antenna ranged from 0 to 17.5 µV. Hence, the thermoelectric device based in microstrip nanoantennas has a responsivity of 1.75 µV/mW.

A low-cost, low-profile, high-performance antenna array based on a 4×4 series-fed patch with elliptical slots is presented in this article for fifth-generation millimeter-wave communications (5G mmWave). The antenna array can be manufactured easily on a two-layer printed circuit board because of its simple design and lack of complex structures. It is designed for the Ka-band (n257 band) with an impedance bandwidth of 3.1 GHz, covering the range from 26.1 GHz to 29.2 GHz. There is a fractional bandwidth of about 11.2%, several times greater than the fractional bandwidth of a series-fed antenna. Within the impedance bandwidth, the radiation gain exceeds 11 dBi, with a maximum gain of 18.25 dBi. The radiation efficiency reaches an impressive 94% and the aperture efficiency reaches 44.6%. The isolation between the four excitation ports is less than −30 dB. Additionally, the 70% impedance bandwidth features right-hand elliptical polarization with a 3:1 axial ratio. It also has an excellent beam steering range (theta angle: $��\; ��{�\pm �\; �45�}^o��$). The following section will provide a detailed description of the antenna array and an analysis of the resonance frequencies. Further, the array antenna is combined with the Butler matrix network to form a beamforming function. Finally, the measured results agree well with the simulation results. This low-cost, low-profile, high-performance antenna array will promote the popularization of 5G mmWave communications, which will be widely used worldwide.

In this study, we introduce a novel optical thermometer utilizing surface plasmon resonance for single-wavelength, real-time measurements, eliminating the need for extensive data analysis. We define operational temperature intervals and assess sensitivity to temperature variations in water within each interval, with a maximum sensitivity of approximately −1.3% per°C at an incidence angle of 66.5°. This approach offers potential integration with existing biological or chemical sensors, facilitating real-time monitoring of both endothermic and exothermic reactions. Our results show that the thermometer is highly sensitive and accurate within a temperature range of 15°C to 45°C, with an RMSE of 0.02°C during the cooling process. Experimental data align closely with numerical calculations. Additionally, thermographic measurements provided visual and quantitative data on the temperature distribution on the sensing surface, allowing for a better understanding of the thermal behavior of the sensor. The primary advantage of this device is its ability to provide instantaneous temperature readings, making it particularly suitable for integration with existing biological and chemical sensors.

The new electric power system, dominated by renewable energy sources, demands current transformers with wide bandwidth and broad dynamic sensing capabilities. An all-fiber optic that combines fiber optic sensing technology with the Faraday magneto-optical effect offers an effective solution for precise dynamic current sensing. The paper first introduces the principle and basic optical path structure of the all-fiber optic current transformer (AFOCT), followed by a discussion on the error factors affecting the measurement performance and operational reliability of AFOCT. It then summarizes and presents specific solutions developed over the past decade. Lastly, the paper concludes with a summary and future outlook on applying AFOCT in power grids. Optical current transformers are currently widely used in ultrahigh and extra-high voltage transmission engineering. As optical current transformer technology matures, coupled with advancements in intelligence levels, the prospects in the field of current measurement are broad and promising.

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.