Microwave and Optical Technology Letters最新文献

This paper presents a compact multiband antenna design optimized for smartwatch applications, capable of supporting multiple wireless standards including GPS (1.575 GHz), Bluetooth/Wi-Fi (2.4 GHz), Wi-Max (3.3 GHz), and the upper Wi-Fi band (5.2 GHz). The proposed antenna with dimensions of 35 × 36 × 0.27 mm³, is fabricated on a Rogers RO4003C substrate (εᵣ = 3.8). Experimental results show peak gains of 1.3, 1.98, 2.69, and 3.6 dBi at 1.575, 2.4, 3.3, and 5.2 GHz, respectively. The measured return loss (S₁₁) is consistently below −10 dB across all operating bands, indicating excellent impedance matching. The antenna demonstrates radiation efficiency between 70% and 75%, outperforming traditional smartwatch antennas by 15% to 20%. By incorporating parasitic elements and a novel meandering structure, the design achieves a 30% reduction in antenna size and a 32% increase in bandwidth compared to conventional designs. This work offers a promising solution for next-generation smartwatch applications, balancing compact size, multi-band operation, and robust performance.

We present a millimeter-wave (mm-wave) emitter featuring a monolithically integrated, high-performance germanium (Ge) photodetector (PD) coupled with an impedance-matched on-chip antenna on a silicon photonic platform. Utilizing the standard multilayer electrode fabrication process in silicon photonics, we design the on-chip antenna in the upper metal layer. We make specific adjustments to the shape and size of the antenna excitation ports and the intermediate metal layer electrode leads based on the structure of the output electrodes of the Ge detector. This constitutes a substantial breakthrough compared to the traditional bowtie antenna designs that do not include routing plans. The Ge PD exhibits a dark current of 273 nA and a responsivity of 0.86 A/W at a bias of −2 V, ensuring the high system's sensitivity and energy efficiency. Additionally, a high-resistance silicon lens further strengthens the antenna's directional radiation and gain. The mm-wave emitter achieves a power output of 10.6 nW at an antenna resonance frequency of 34.96 GHz, measured at a distance of 10 cm without an external amplifier. This integrated mm-wave emitter is particularly suitable for on-chip and inter-chip wireless links for high-bandwidth data transfer in densely integrated microwave photonic systems. The monolithic integration significantly reduces parasitic losses and enables scalable deployment of antenna–PD units in future silicon photonic platforms.

To achieve efficient modeling of unidirectional fine structure and accurate analysis of far-field characteristics, a practical scheme applying the nonuniform grid (NG) and convolution perfectly matched layer (CPML) in the hybrid implicit-explicit (HIE) finite-difference time-domain (FDTD) method is investigated. The numerical stability of the proposed method is rigorously demonstrated analytically, and its effectiveness is verified by simulation analysis and experimental comparison of antenna examples. The computational efficiency is improved 16.7% compared to the HIE-FDTD method, and memory usage is significantly reduced through targeted discretization with NG and stability maintenance via CPML.

A dual-band co-design which integrates a partially reflective surface with a linear-to-circular polarization converter is proposed and utilized for the design of a dual-band diverse-circularly polarized (CP) Fabry-Pérot antenna. The classical ray-tracing approach based on multiple reflections and transmissions is developed and simplified, and the design basis for the polarization converter is derived. An antenna primarily composed of a single-fed patch source and a chiral multifunctional metasurface is designed and presented subsequently. The antenna is simulated, followed by fabrication and measurement. Measured results indicate that the antenna radiates right-hand CP and left-hand CP waves with the frequency range of (9.2~9.8 GHz and 13.5~14.2 GHz), respectively. Besides, the peak realized gains within the two operation bands are 15.8 and 16.6 dBic, respectively.

Antenna directional pattern measurements can be generally categorized into near-field and far-field measurements. The measurement algorithm designed in this paper is based on the use of Fourier interpolation of band-limited periodic functions under far-field conditions to achieve accurate and fast measurements. The antenna far-field measurement process is generally required to be both accurate and fast, in order to measure accurately, the denser the scanning sampling cutting plane is, the better (the sampling interval for far-field measurement is usually less than 0.1 of the Half Power Beam Width). However, with the development of antenna arrays, there are more and more large aperture phased scanning arrays, and these antennas with narrower half power beam width (HPBW) are sampled very much in 360° scanning range in order to measure accurate pattern in far-field measurement, which obviously reduces the measurement efficiency of the antenna. However, the algorithm proposed in this paper is able to realize the sampling interval as the order of magnitude of HPBW on the basis of Fourier interpolation, which can not only realize the accurate measurement of far-field pattern but also greatly save the measurement time and improve the measurement efficiency. In the paper, several antennas are utilized to prove the feasibility of the algorithm, which shows that the proposed algorithm can not only accurately realize the measurement of the far-field of the directional pattern but also improve the efficiency of the measurement.

A wideband absorber with large angle absorption capabilities is designed based on cross strip embedded loop. Strong coupling between the cross strip and the loop is utilized to enlarge the absorbing bandwidth, and a new equivalent circuit model considering the coupling is proposed for analysis. The reflection coefficient of a 23 × 23 unit cells array was experimentally determined. The absorber exhibits a −10 dB reflection coefficient of 5.11–19.07 GHz (115%) for the normal incidence. Notably, at an incident wave angles of 45° and 60°, the absorber still maintains a wide band for transverse electric (TE) and transverse magnetic (TM) polarizations. Using only two substrate layers and one air space layer, the proposed absorber exhibits a simple structure.

To meet the requirements of wide-range and high-precision radar detection, a beamformed substrate integrated waveguide (SIW) slot array antenna is presented and investigated. The proposed antenna achieves a broadened beamwidth pattern with low sidelobe levels (SLLs) while maintaining a required gain level in H-plane and simultaneously realizes a cosecant-squared beam pattern in E-plane for high-precision detection. The antenna comprises 32 series-fed standing wave slot arrays, each containing 12 slot elements. To achieve wide beam coverage under a prescribed gain constraint, a genetic algorithm (GA) is introduced to synthesize the special radiation patterns. The optimization process employs amplitude weighting of the series-fed units to achieve a broadened beam by shifting the first null outside the target range in H-plane, while amplitude and phase weighting are applied to realize a cosecant-squared radiation pattern covering 0° to 30° in E-plane. A 32 × 12 SIW slot array antenna operating in the 9.2–9.6 GHz band is designed and fabricated. Measurement results demonstrate an H-plane pattern free of nulls within ±16° with low SLLs below −28.1 dB, and a cosecant-squared beam from 0° to 30° in the E-plane with SLLs suppressed to- 20 dB. The achieved performance indicates that the overall methodology is well-suited for such slot antenna arrays.

Frequency offset (FO) has significant influence on the performance of frequency diverse array (FDA). To improve the range resolution of FDA, a transmit-receive beamforming approach with optimized arsinh-type FO is proposed in this article. In specific, two tunable parameters are introduced into the arsinh-type FO to search for the optimal FOs for a linearly spaced FDA (linear-FDA) with uniform weight values. Both the peak sidelobe level and mainlobe width in range dimension are incorporated into the optimization problem. Simulation results demonstrate that the proposed approach can provide superior performance in spatial focusing, sidelobe suppression, and range resolution.