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To address the challenges posed by propagation channel impairments and to meet the high data rate requirements of laser communications, this study introduces a pioneering low-density parity-check (LDPC) decoder characterized by its high throughput and low complexity. The unique design of this decoder, based on an inter-frame pipeline and intra-frame parallel (IFPP-IFP) scheme, is specifically tailored to maximize the efficiency of processing units, leading to a substantial increase in decoding throughput. The implementation of IFPP is realized through a novel full-overlap message passing (FOMP) scheme and a dynamic address access (DAA) algorithm, distinguishing it from current solutions. Additionally, the decoder employs a message packing strategy and low-complexity data alignment units to effectively achieve IFP. Compared to existing solutions, our hardware implementation on the Xilinx XCKU060 FPGA demonstrates significant progress. The decoder achieves a decoding throughput of 2.67 Gb/s at 10 iterations and 350MHz. Remarkably, when five decoders are used on a single FPGA device, the throughput soars to 13.3 Gb/s, outperforming state-of-the-art designs by 1.3 times and concurrently reducing resource consumption by half. This combination of resource efficiency and enhanced throughput highlights the innovative and superior nature of our proposed approach.

Unmanned Aerial Vehicle (UAV) infrared detection has problems such as weak and small targets, complex backgrounds, and poor real-time detection performance. It is difficult for general target detection algorithms to achieve the requirements of a high detection rate, low missed detection rate, and high real-time performance. In order to solve these problems, this paper proposes an improved small target detection method based on Picodet. First, to address the problem of poor real-time performance, an improved lightweight LCNet network was introduced as the backbone network for feature extraction. Secondly, in order to solve the problems of high false detection rate and missed detection rate due to weak targets, the Squeeze-and-Excitation module was added and the feature pyramid structure was improved. Experimental results obtained on the HIT-UAV public dataset show that the improved detection model’s real-time frame rate increased by 31 fps and the average accuracy (MAP) increased by 7%, which proves the effectiveness of this method for UAV infrared small target detection.

Spaceborne synthetic aperture radar (SAR) is an advanced microwave imaging technology that provides all-weather and all-day target information. However, as spaceborne SAR resolution improves, traditional echo signal models based on airborne SAR design become inadequate due to the curved orbit, Earth rotation, and increased propagation distance. In this study, we propose an accurate range model for high-resolution spaceborne SAR by analyzing motion trajectory and Doppler parameters from the perspective of the space geometry of spaceborne SAR. We evaluate the accuracy of existing range models and propose an advanced equivalent squint range model (AESRM) that accurately fits the actual range history and compensates for high-order term errors by introducing third-order and fourth-order error terms while maintaining the simplicity of the traditional model. The proposed AESRM’s concise two-dimensional frequency spectrum form facilitates the design of imaging algorithms. Point target simulations confirm the effectiveness of the proposed AESRM, demonstrating significant improvements in fitting accuracy for range histories characterized by nonlinear trajectories. The developed AESRM provides a robust foundation for designing imaging algorithms and enables higher resolution and more accurate radar imaging.

Simulated raw data have become an essential tool for testing and assessing system parameters and imaging performance due to the high cost and limited availability of real raw data from spaceborne synthetic aperture radar (SAR). However, with increasing resolution and higher orbit altitudes, existing simulation methods fail to generate SAR simulated raw data that closely resemble real raw data. This is due to approximations such as curved orbits, “stop-and-go” assumption, and Earth’s rotation, among other factors. To overcome these challenges, this paper presents an accurate range model with a “nonstop-and-go” configuration for raw data simulation based on existing time-domain simulation methods. We model the SAR echo signal and establish a precise space geometry for spaceborne SAR. Additionally, we precisely identify the target illumination area based on elliptical beams through space coordinate transformation. Finally, the SAR raw data were accurately simulated using high-precision time-domain simulation methods. The accuracy of the proposed model was validated by comparing it with the traditional hyperbolic model and the curved orbit model with “stop-and-go” assumption through image processing of the generated raw data. Through the analysis of point target quality parameters, the errors of various parameters in our distance model compared with the other two models are within 1%. Furthermore, this simulation method can be adapted to simulate raw data of other modes and satellite orbits by adjusting beam control and satellite orbit parameters, respectively. The proposed simulation method demonstrated high accuracy and versatility, thereby providing a valuable contribution to the development of remote sensing technology.

Trackers based on Siamese networks show great potential in tracking accuracy and speed. However, it is still challenging to adapt offline training model to online tracking. In this paper, a Siamese based tracker (SCRPN-CISA) is proposed, which integrates three attention mechanisms and a novel Cascaded Region Proposal Networks (RPN) architecture, for improving the feature extraction ability, adaptability and discrimination ability in complex scenes. Firstly, the deep network VGG-Net-D is adopted as the backbone network in the Siamese framework to increase the feature extraction capability. Then, a Channel-Interconnection-Spatial Attention module is constructed to enhance the adaptive and discriminative capability of the model. Next, a Deconvolution Adjust Block is built to fusion cross-layer features. Finally, a Three-Layer Cascaded RPN is conceived to acquire the foreground-background classification and bounding box regression by correlation calculation, and moreover, a proposal region screening strategy is presented to obtain more accurate tracking results. Experiments on OTB-2015, UAV123, VOT2016, and VOT2019 benchmarks demonstrate that, the proposed tracker (SCRPN-CISA) achieves competitive performance compared with the state-of-the-art trackers.

In the practical direction of arrival (DOA) estimation applications, it is required that the multichannel signal acquisition equipment can synchronously collect the signals received by the array antenna. In addition, the signal phase relationships between channels are supposed to be stable. However, this kind of equipment is usually complex and expensive to manufacture. Since some SDR devices are reconfigurable and open source, this paper adopts HackRF Ones as the signal sampling devices to design the DOA estimation system. The clocks line is used to synchronize the clock frequencies between HackRF Ones. Besides, an external pulse is introduced to control the sampling devices to start sampling simultaneously. In this case, the stable phase difference between channels can be obtained. The experimental results show that the synchronization error between channels of the system is less than one sampling period. The system can be used to estimate the incident angles of single carrier signals or modulated signals. The RMS errors of the system when estimating one source and two sources are 1.94° and 2.85°, respectively.

With the rapid development of the world’s aerospace technologies, a high-power and high-reliability space high-voltage power supply is significantly required by new generation of applications, including high-power electric propulsion, space welding, deep space exploration, and space solar power stations. However, it is quite difficult for space power supplies to directly achieve high-voltage output from the bus, because of the harshness of the space environment and the performance limitations of existing aerospace-grade electronic components. This paper proposes a high-voltage power supply module design for space welding applications, which outputs 1 kV and 200 W when the input is 100 V. This paper also improves the efficiency of the high-voltage converter with a phase-shifted full-bridge series resonant circuit, then simulates the optimized power module and the electric field distribution of the high-voltage circuit board.

Compared with conventional methane reforming technologies, chemical looping reforming (CLR) has the advantages of self-elimination of coke, a suitable syngas ratio for certain down-stream processes, and a pure H2 or CO stream. In the reduction step of CLR, methane combustion has to be inhibited, which could be achieved by designing appropriate oxygen carriers and/or optimizing the operating conditions. To gain a further understanding of the combustion reaction, methane oxidation by perovskite (SrFeO3-δ) at 900 °C and 1 atm in a pulse mode was investigated in this work. The oxygen non-stoichiometry of SrFeO3-δ prepared by a Pechini-type polymerizable complex method is 0.14 at ambient conditions, and it increases to 0.25 and subsequently to 0.5 when heating from 100 to 900 °C in argon that contains 2 ppmv of molecular oxygen. The activation energies of the first and second transitions are 294 and 177 kJ/mol, respectively. The presence of 0.99 vol.% hydrogen in argon significantly reduces the amount CO2 produced. At a pulse interval of 10 min, the amount of CO2 produced in the absence of hydrogen is one order of magnitude greater than that in the presence of hydrogen. In the former case, the amount of CO2 produced dramatically decreases first and then gradually approaches a constant, and the oxygen species involved in methane combustion can be partially replenished by extending the pulse interval, e.g., 82.5% of this type of oxygen species is replenished when the pulse interval is extended to 60 min. The restored species predominantly originate from those that reside in the surface layer or even in the bulk. [ABSTRACT FROM AUTHOR]

We analysed the effects of black geotextile inter-row mulch, grass mulch and clean tillage as a control on the microclimate, anthocyanin components and fruit quality of 'Xinyu' table grape in a semi-arid climate. Black geotextile inter-row mulch increased the air and soil temperatures, while grass mulch decreased these. Six types of anthocyanins were detected in the grapes. Around 50% of the total anthocyanins were malvidin based (38.60%–39.10%) and peonidin based (25.80%–31.10%), with malvidin-3-O-glucoside being the main pigment (38.75%–39.05%), followed by peonidin-3-O-glucoside (23.84%–28.68%). The soluble solid content, reducing sugar content and sugar-acid ratio for the black geotextile treatment group were 12.93%, 10.05% and 25.85% higher, respectively, than the control. By contrast, grapes in the grass mulch treatment group had a significantly lower soluble solid content than the control, with a 7.32% reduction being observed. Neither type of mulch had a large effect on the vitamin C content nor yield. However, both black geotextile inter-row mulch and grass mulch could regulate the orchard microclimate and increased the total anthocyanin content by 36.04% and 5.03%, respectively, compared with the control. These findings suggest that grass mulch is the preferable cultivation method in the Turpan area. [ABSTRACT FROM AUTHOR]

With the advancement of spaceborne synthetic aperture radar (SAR) resolution, the conventional stop-and-go approximation-based motion model is no longer suitable for high-resolution imaging algorithms. This paper conducts a comprehensive analysis of the approximation errors resulting from the stop-and-go approximation and proposes corresponding compensation methods. Firstly, an accurate echo model based on continuous platform motion is derived from the SAR geometry configuration. The impact of these errors on range and azimuth imaging is analysed from a spectral perspective, and the applicable boundary conditions are examined. Subsequently, compensation methods are proposed to eliminate the introduced approximation errors, addressing both"fast time" and"slow time" effects, thus enabling high-resolution imaging through improvements in traditional imaging algorithms. Experimental simulations validate the effectiveness of the error analysis and compensation methods, using X-band low Earth orbit SAR as an illustrative example. The proposed methods are not only compatible with existing mature imaging algorithms, but the analytical approach and compensation methods are also applicable to SAR systems operating on different carrier frequencies, orbits, and platforms. [ABSTRACT FROM AUTHOR]