This letter proposes a novel high-selectivity quad-band bandpass filter (BPF) with nine transmission zeros (TZs) using asymmetrical interdigital coupled lines and circular spiral lines. By deploying ...five asymmetrical circular interdigital coupling lines, a quad-band BPF with seven TZs is achieved. With adding two open circular spiral lines, two additional independent TZs are obtained. The nine controllable TZs contribute to selectivity improvement significantly. The fabricated BPF demonstrates four passbands located at 2.4, 3.5, 4.5, and 5.8 GHz, which are suitable for Wi-Fi and 5G communication. Within the four passbands, the minimum insertion losses are 1.3, 0.9, 2.2, and 1.3 dB, and the shape factors are 2.4, 1.8, 1.9, and 1.9, respectively. The overall size of the fabricated filter is <inline-formula> <tex-math notation="LaTeX">15.5 \times 22.5 </tex-math></inline-formula> mm 2 . Compared with the other double-layered works, this letter demonstrates significantly enhanced selectivity and competitive insertion loss.
In order to improve the channel capacity, waves carrying orbital angular momentum (OAM) in communication systems have attracted much attention. A two-OAM-mode antenna system, which works at 2.4 GHz, ...is proposed in this paper. And a signal transmission experiment is performed based on a pair of the proposed antenna systems. The proposed antenna system, which has the planar structure, is composed of two patch antenna arrays, two feeding networks, and one common ground plane. Then, reflection coefficients, transmission coefficients, radiation patterns, and phase distributions of the proposed antenna system are measured, and the measurement results verify the effectiveness of this antenna system in generating two OAM modes (OAM mode 1 and OAM mode 2). The measurement results are in good agreement with the simulation results. Then, the signal transmission system is built based on a pair of the proposed antenna systems. Isolation between the OAM mode 1 transceiver channel and the OAM mode 2 transceiver channel is more than 20 dB. Video signals modulated by filter bank multicarrier are de-modulated simultaneously at the receiving terminal. It means that the two-OAM-mode antenna system has the potential to enhance the channel capacity.
In this paper a new approximate fast method of calculating the bistatic‐scattering coefficients of a multilayer structure with random rough interfaces was presented based on the Kirchhoff ...Approximation (KA) and the electromagnetic theory of stratified media. First, the electromagnetic scattering from a Gauss rough metal or dielectric surface was calculated by KA method and method of moment (MOM), and the effectiveness of KA method was confirmed and verified. Second, a new approximate fast method was presented to calculate electromagnetic scattering from a multilayer‐random‐rough surface based on electromagnetic reflection from multilayer parallel surfaces and KA. The calculated results by the new method were in good agreements with those by MOM, especially near the specular point. Finally, a comparison of the new method and MOM was carried out in consuming computing time, memory resources, and complexity. The comparison indicated that the new approximate method was faster by about 30–150 times than MOM. The new approximate fast method could avoid a large matrix inversion and greatly reduce the computation time and memory resources and thus improve the computational efficiency. It was an effective approximation fast analyzing method of electromagnetic scattering from multilayer rough surfaces.
Key Points
A new approximate fast method of calculating the scattering from random rough interfaces is presented
Combing electromagnetic reflection from multilayer parallel surfaces and KA
The new approximate fast method is faster by 30–150 times than MOM
In this letter, two simple and novel circular slot antenna systems to generate OAM waves are proposed. Special feeding networks, which can be used to generate two OAM modes, are designed at 2.4 GHz ...to feed the circular slot antenna. Furthermore, two antenna systems are fabricated and tested. Both the simulation and measurement results demonstrate the effectiveness of the antenna systems for generating OAM waves.
Perovskite oxides have emerged as alternative anode materials for hydrocarbon‐fueled solid oxide fuel cells (SOFCs). Nevertheless, the sluggish kinetics for hydrocarbon conversion hinder their ...commercial applications. Herein, a novel dual‐exsolved self‐assembled anode for CH4‐fueled SOFCs is developed. The designed Ru@Ru‐Sr2Fe1.5Mo0.5O6‐δ(SFM)/Ru‐Gd0.1Ce0.9O2‐δ(GDC) anode exhibits a unique hierarchical structure of nano‐heterointerfaces exsolved on submicron skeletons. As a result, the Ru@Ru‐SFM/Ru‐GDC anode‐based single cell achieves high peak power densities of 1.03 and 0.63 W cm−2 at 800 °C under humidified H2 and CH4, surpassing most reported perovskite‐based anodes. Moreover, this anode demonstrates negligible degradation over 200 h in humidified CH4, indicating high resistance to carbon deposition. Density functional theory calculations reveal that the created metal‐oxide heterointerfaces of Ru@Ru‐SFM and Ru@Ru‐GDC have higher intrinsic activities for CH4 conversion compared to pristine SFM. These findings highlight a viable design of the dual‐exsolved self‐assembled anode for efficient and robust hydrocarbon‐fueled SOFCs.
To achieve efficient and robust CH4 fueled solid oxide fuel cells, a hierarchical Ru@Ru‐Sr2Fe1.5Mo0.5O6‐δ (SFM)/Ru‐Gd0.1Ce0.9O2‐δ (GDC) anode is developed by an innovative integration of self‐assembly and dual exsolution. The single cell using this anode delivers a high peak power density of 0.63 W cm−2 at 800 °C and a remarkable stability for 200 h using humidified CH4 as fuel.
Surface orientation information is essential to depicting the 3-D structure of an object. This paper analyzes the linear polarization characteristics of several typical objects by simulations and ...measurements. Then, a polarization-based method is presented to acquire the object surface orientation information from three different linear polarization brightness temperature images by using a 94-GHz imaging radiometer. The experiments are conducted outside, where a wooden plate is placed obliquely on a metal box. Experimental results indicate that our method is capable of achieving the surface orientation information that is beneficial to recognizing the object. This method suggests possible applications for terrain models and object detections.
In order to quantitatively interpret topographic effect on Chang'E (CE) microwave data, a detailed method to compute brightness temperature (TB) over a lunar crater is proposed, which incorporated ...the effect of surface tilts. The method improves the effective solar irradiance model of the lunar surface to obtain the temperature profile of the lunar crater. The calculated TB at 37 GHz with the proposed computation method, which is based on three digital elevation models (DEMs) from different sources, are consistent with the observed TB from the CE-2 microwave radiometer. The simulated behavior of TB across crater Hercules reproduces the TB undulation observed by CE in a single swath. TB is significantly affected by the lunar dust of a lunar crater and affected by albedo and emissivity in a lesser degree. Based on the explanation with simplified models, the TB variation over a crater is proved to be significantly affected, through physical temperature, by the crater shape described by DEMs. With the simplified crater model, the amplitude of the TB oscillatory curves is proved to depend on the crater shape.
Monopole patch antenna systems, which can generate orbital angular momentum (OAM) waves at 2.4GHz, are proposed in this paper. The proposed antenna systems have advantages of simple planar structure ...and small size of antenna element. Design, simulation, fabrication and measurement of the proposed antenna systems are presented. Two feeding networks, which constitute the proposed antenna systems with monopole patch antenna array, are designed to generate modes 1 and 2 of OAM waves. The antenna systems for both modes are shown to be effective in generating OAM waves of modes 1 and 2 from both simulation and three types of measurement: radiation pattern, phase distribution and phase gradient. Simulation and measurement results of radiation pattern and phase distribution have shown very close results. Phase gradient measurement results has verified that the generated waves from the antenna systems are indeed OAM waves.
Antenna array configurations have significant influence on the radiometric sensitivity of aperture synthesis microwave radiometers. In this paper, we propose a minimum degradation array (MDA) for ...optimum sensitivity. First, the degradation factor (DF) is defined to characterize the effect of redundant spatial frequency samples formed by an array on the sensitivity. Aiming at minimizing DF, a simulated annealing (SA) based method is proposed to search for an MDA, which, combining with a concept of augmented maximum baseline (CAMB), can effectively locate the true global minimum of DF. Numerical results validate the effectiveness of the proposed method as well as CAMB in optimizing DF. Further, the lower bound of DF is discussed. Finally, simulation and experiment results demonstrate that the proposed method as well as CAMB is of significance in achieving optimum sensitivity.
For one-dimensional aperture synthesis microwave radiometers, the optimal placement of antenna elements in a low-redundancy linear array (LRLA) is difficult when large numbers of elements are ...involved. In this paper, the general structure of large LRLAs is summarized first, and then a novel stochastic optimization technique, ant colony optimization (ACO), is applied to the search for low redundancy arrays. By combining the general structure with the ACO procedure, an efficient method is proposed for a rapid exploration for optimal array configurations. Numerical studies show that the method can generate various large LRLAs with lower redundancy than the previous algorithms did and the computational cost is greatly reduced. Based on the method, several analytical patterns for LRLAs are further derived, which can yield various array configurations with very low redundancy in nearly zero computation time. Both the method and the resulting configurations can be utilized to facilitate antenna array design in synthetic aperture radiometers with high spatial resolution.
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