Microwave and Optical Technology Letters最新文献

This letter presents a filtering Wilkinson power divider (WPD) with good in-band and out-of-band performance based on a filtering impedance inverter (FII). The FII consists of a high-pass filter (HPF) and a low-pass filter (LPF). This FII is capable to produce a required value of phase shift at the designed frequency and matched with any impedance value. To validate this, the quarter wavelength lines of conventional WPD having an impedance of 70.7 Ω are replaced by FII. Therefore, the proposed power divider provides bandpass response and power division simultaneously within a small circuit area. The physical area of the proposed power divider occupies only 30% (0.12λ_g × 0.16λ_g, where λ_g is guided wavelength) circuit area of the conventional WPD. Moreover, the in-band return loss and isolation were better than 30 dB and the out-of-band rejection level was better than −25 dB up to 6.5f₀ obtained.

In this study, we design an all-metal tunable broadband frequency selective surface (FSS) that eliminates the need for lossy dielectric substrates and active devices requiring complex bias DC voltage-based control circuits. The FSS is constructed from three cascaded all-metallic plates, each comprising cells formed by uniting two concentric four-arm substructures. Those cascaded configuration exploits multi-order filtering to obtain broadband and independently controllable odd-mode resonance to generate tunable bandpass response. The operating mechanism of the proposed FSS is analyzed and verified by the results from full-wave simulation, equivalent circuit calculation, and mode-related analysis. The measured and simulated results show that the structure can provide a tunable bandwidth range from 6.40 to 10.0 GHz, with a maximum bandwidth of 43%. Additionally, the FSS maintains low insertion losses and stable performance for both TE and TM polarization across a wide range of incidence angles.

In this paper, we present an unequal-order bandpass filter (BPF) using packaged multilayer metal-integrated suspended line (MISL) technology. Our proposed multimode hybrid resonant cells combine high-$��\; ��Q��$ patches and slotline modes, allowing for the achievement of three independent controllable frequencies and compact sizes. The key advantage of this resonator is the ability to collect and utilize different resonance modes, enabling the design of unequal-order dual-band BPFs. To validate the effectiveness of the proposed concept, a series of filters with unequal orders were simulated. Additionally, a filter (third-order for the first passband and sixth-order for the second passband) was designed, simulated, and tested. The test results demonstrated that the unequal-order filters proposed by us possess advantages of wide bandwidth, low loss, and unequal-order filtering responses.

In local networks and other short links, polymeric optical fiber may be used due to its mechanical properties; however, some undesired and strong effects appear in these environments. This work proposes three different models to fine-tune the electrical parameters of discrete multi-tone (DMT) modulation to predict the signal-to-noise rate (SNR) over each subcarrier used with a 560 nm central wavelength. Considering the present setup, the devised models achieve some bold results, demonstrating the possibility of explaining more than 99% of the experimental data, in the best scenario. Several models are mathematically fit to obtain distinct adjustments for the nonlinearity present in the link considering the electrical parameters.

Detail enhancement and noise suppression are critical to the performance of infrared imaging systems, and a method for enhancing infrared images based on guided filters is introduced in this paper. Firstly, the guidance filter and Gaussian filter are used to decompose the original infrared image into the base layer and the detail layer, and then the adaptive histogram equalization method is used to enhance the overall brightness and contrast of the base layer. For the detail layer, we will guide the filtering to obtain the gain factor through the “$��\; ��3�\; �\sigma ��$” rule processing, on this basis, the detail gain function is constructed to apply to the processing of the detail layer, and finally the basic layer and the detail layer are fused to obtain the final result image. The proposed method is compared with six other infrared image enhancement algorithms under different data sets and analyzed using subjective and objective evaluation indicators. The experimental data show that the proposed method can effectively improve the overall contrast and local details of the image and has good scene adaptability. Finally, we transplanted the algorithm to the FPGA bottom layer for implementation, and for 640 $��\; ��\times ��$ 512 resolution images, the final implementation effect is almost no different from that on the PC side.

The proposed article offered a closely packed circularly polarized MIMO antenna system for a 5G NR n48/n78 communication system. The design consists of an E-shaped antenna with modified arms along with shorting pins, and the edge-to-edge distance between the radiator is 0.2 mm. The proposed design offers isolation from 15 dB(minimum) to 47.35 dB(maximum) in the range of 3.3 to 3.9 GHz with a peak gain of 4.2 dBi. The uniqueness of this design here is the surface current cancellation technique within the design space of this E-shaped antenna, which decouples the radiators with high compaction and reduces complexities. To verify the design, the diversity parameters, efficiency, radiation pattern, in-hand performance, and SAR (specific absorption rate) are calculated, and the results are in good agreement with the measured results. From the above analysis, we can conclude that the proposed closely packed circularly polarized MIMO design can be a good candidate for 5G mobile communication.

In this paper, a novel balanced nonreciprocal bandpass filter based on stub-loaded ring time-modulated resonators (TMRs) is proposed, which is co-designed to integrate the feed circuits and common-mode (CM) suppression circuits. The design employs the fewest TMRs necessary, which is at least two, to achieve a reverse isolation level of larger than 20 dB. This configuration also ensures the presence of two reverse isolation poles, thereby maximizing the reverse isolation bandwidth. Even- and odd-mode analysis elucidates the isolation of signals under differential mode (DM) and the suppression of noise under common mode. This approach eliminates the need for separate feed lines and complex CM noise suppression circuit designs. Furthermore, parameterization analysis is adopted to verify the modulation parameters on the impact of the circuit. A balanced microstrip nonreciprocal bandpass filter, centered at 1.5 GHz, has been designed, simulated, and experimentally verified. The measured DM forward insertion loss is 3.9 dB, and the reverse isolation is greater than 20 dB with a bandwidth of 48 MHz. The measured CM noise suppression exceeds 26.6 dB within the frequency range of 1.2 to 1.8 GHz.

This paper presents the design and fabrication of a 4×4 array antenna based on multi-mode horn elements and sequential feeding network. The multi-mode horn antenna is a structure that can suppress grating lobes and side lobe levels by excitation and combining different modes of electromagnetic wave radiation. The sequential feeding network is a technique that can generate circularly polarized radiation from linearly polarized elements by arranging them in a square array with 90° rotations and feeding them with 90° phase difference. The proposed array antenna achieves wideband impedance matching and axial ratio performance, as well as high gain and low complexity. The array antenna operates from 9.9 to 12.6 GHz, with a maximum gain of 24.5 dBi at 11 GHz. The array antenna is fabricated using CNC milling and measured in an anechoic chamber. The measured results agree well with the simulated ones, validating the effectiveness of the proposed design.

A new type of intermediate-frequency (IF) filter based on LTCC multilayer technology for BeiDou navigation satellite system is presented in this letter. By reasonably selecting the equivalent circuit value of each passive component, and separating the effective area of each inductance and capacitance to reduce the influence of parasitic coupling, an IF bandpass filter with a center frequency of only 46 MHz can be realized in a ceramic surface mount package. Besides, the locations of the transmission zeros can be tuned individually by changing the LC value of each resonant cell, thus a deep suppression level and wide stopband could be obtained simultaneously. The IF filter has a compact size of 10 mm × 6 mm × 2 mm, which is very suitable for the portable BeiDou B3 system.

This letter proposes a new design of a dual-band (DB) filtering power divider (FPD) on a single multimode-modified triangle patch resonator. The proposed design leverages the resonant characteristics of an equilateral triangle patch resonator to exploit the TM₁₀, TM₁₁, TM₂₁, and TM₃₀ resonant modes within a single multimode-modified triangle patch resonator, enabling the realization of an FPD with DB operation. To achieve two assumed second-order filtering passbands, a metal via and multiple perturbed slots are introduced, providing flexible control over the resonant mode frequencies. The first passband is formed by the TM₁₀ and TM₁₁ modes, while the second passband is formed by the TM₂₁ and TM₃₀ modes. To ensure in-band isolation for both passbands, two sets of isolation networks are developed. A prototype is designed, fabricated, and measured to validate the proposed method. The measured results demonstrate excellent agreement with the simulated ones.