Near Field 3-D Millimeter-Wave SAR Image Enhancement and Detection with Application of Antenna Pattern Compensation.

In this paper, a novel near-field high-resolution image focusing technique is proposed. With the emergence of Millimeter-wave (mmWave) devices, near-field synthetic aperture radar (SAR) imaging is widely used in automotive-mounted SAR imaging, UAV imaging, concealed threat detection, etc. Current research is mainly confined to the laboratory environment, thus ignoring the adverse effects of the non-ideal experimental environment on imaging and subsequent detection in real scenarios. To address this problem, we propose an optimized Back-Projection Algorithm (BPA) that considers the loss path of signal propagation among space by converting the amplitude factor in the echo model into a beam-weighting. The proposed algorithm is an image focusing algorithm for arbitrary and irregular arrays, and effectively mitigates sparse array imaging ghosts. We apply the 3DRIED dataset to construct image datasets for target detection, comparing the kappa coefficients of the proposed scheme with those obtained from classic BPA and Range Migration Algorithm (RMA) with amplitude loss compensation. The results show that the proposed algorithm attains a high-fidelity image reconstruction focus.

A New Three-Dimension Deceptive Scene Generation against Single-Pass Multibaseline InSAR Based on Multiple Transponders.

The interferometry synthetic aperture radar (InSAR) deceptive jamming method utilizing two synergetic transponders can generate a false three-dimension (3D) scene in a single baseline InSAR image. However, such deceptive capability could be reduced by the multibaseline InSAR system. To obtain effective deception on multibaseline InSAR, a novel deceptive scene generation method jointly employing multiple transponders is proposed. It only demands that each transponder is modulated with a complex coefficient when generating a false point. The complex modulation coefficient can be offline calculated according to the deceptive point coordinate by solving a matrix. Besides, the complex modulation coefficient can be combined with the deceptive scene template, and thus a large 3D deceptive scene is able to be created quickly in the multibaseline InSAR image by using the fast two-dimension (2D) SAR deceptive scene generation algorithm. As long as the number of transponders is not less than the number of antennas of the multibaseline InSAR system, this proposed method is effective. The effectiveness of the proposed method is validated by computer simulations.

Tunable Microwave Absorbing Devices Enabled by Reversible Metal Electrodeposition.

Tunable microwave absorbers have gained significant interest due to their capability to actively control microwaves. However, the existing architecture-change-based approach lacks flexibility, and the active-element-based approach is constrained by a narrowband operation or small dynamic modulation range. Here, a novel electrically tunable microwave absorbing device (TMAD) is demonstrated that can achieve dynamic tuning of the average reflection amplitude between -13.0 and -1.2 dB over a broadband range of 8-18 GHz enabled by reversible metal electrodeposition. This reversible tunability is achieved by electrodepositing silver (Ag) layers with controlled morphology on nanoscopic platinum (Pt) films in a device structure similar to a tunable Salisbury screen, employing Ag electrodeposited on Pt films as the modifiable resistive layer. Furthermore, this TMAD possesses a simple device architecture, excellent bistability, and multispectral compatibility. Our approach offers a new strategy for dynamically manipulating microwaves, which has potential utility in intelligent camouflage and communication systems.

Rock-Salt MnS0.5Se0.5 Nanocubes Assembled on N-Doped Graphene Forming van der Waals Heterostructured Hybrids as High-Performance Anode for Lithium- and Sodium-Ion Batteries.

Manganese-based chalcogenides would be of latent capacity in serving as anodes for assembling lithium- and/or sodium-ion batteries (LIBs/SIBs) due to their large theoretical capacity, low price, and low-toxicity functionality, while the low electroconductivity and easy agglomeration behavior may impede their technical applications. Here, a solid-state solution of MnS0.5Se0.5 nanocubes in rock-salt phase has been synthesized for the first time at a relatively low temperature from the precursors of Mn(II) acetylacetonate with dibenzyl dichalcogens in oleylamine with octadecene, and the MnS0.5Se0.5 nanocubes have been assembled with N-doped graphene to form a new kind of heterostructured nanohybrids (shortened as MnS0.5Se0.5/N-G hybrids), which are very potential for the fabrication of metal-ion batteries including LIBs and/or SIBs. Investigations revealed that there have been dense vacancies generated and active sites increased via nonequilibrium alloying of MnS and MnSe into the solid-solution MnS0.5Se0.5 nanocubes with segregation and defects achieved in the low-temperature solution synthetic route. Meanwhile, the introduction of N-doped graphene forming heterojunction interfaces between MnS0.5Se0.5 and N-doped graphene would efficiently enhance their electroconductivity and avoid agglomeration of the active MnS0.5Se0.5 nanocubes with considerably improved electrochemical properties. As a result, the MnS0.5Se0.5/N-G hybrids delivered superior Li/Na storage capacities with outstanding rate performance as well as satisfactorily lasting stability (1039/457 mA h g-1 at 0.1 A g-1 for LIBs/SIBs). Additionally, full-cell LIBs of the anodic MnS0.5Se0.5/N-G constructed with cathodic LiFePO4 (LFP) further confirmed the promising future for their practical application.

Fabrication of van der Waals Heterostructured FePSe3/Carbon Hybrid Nanosheets for Sodium Storage with High Performance.

Iron phosphorus triselenide (FePSe3) is attractive for energy applications owing to its interesting layered geometry, electronic structure, and physiochemical property, while it is limited in actual application because of a very long fabrication time of over 7 days. Herein, we report a new synthetic route to a high-quality sheetlike hybrid of iron phosphorus triselenide nanocrystals coated with graphitic carbon (FePSe3/C) as an alternative kind of van der Waals heterostructures for the first time via a pyrolytic process at 600 °C from the precursors of ferrocene, red phosphorus, and selenium in a quartz tube with a significantly shortened reaction time of 24 h and even down to 30 min. Investigations demonstrated that the component phase of FePSe3 in the layered FePSe3/C hybrid nanosheets is the rhombohedral phase, and the hybrid nanosheets other than bulk crystals are about 15 nm in thickness. Acting as a cathode in fabricating half-cell sodium-ion batteries, the layered FePSe3/C hybrid nanosheets exhibited remarkable performance. Typically, when current density was set as 50 mA g-1, the hybrid nanosheet-assembled battery exhibited a capacity of 182.7 mA h g-1 after performing over 50 cycles, and the nanosheet battery exhibited a capacity of 142 mA h g-1 after performing for 200 cycling trials at 1 A g-1 in the 0.8-2.2 V voltage window. Meanwhile, the layered FePSe3/C hybrid nanosheets also exhibited very high rate capabilities at a relatively large current density in the present study, that is, 172 and 95 mA h g-1 under typical performing conditions at 0.5 and 5 A g-1, respectively.