Ocean internal wave is a common and significant ocean phenomenon that occurs between different density layers in the ocean. In this study, 92 Sentinel-1 images containing internal solitary waves, collected from 2015 to 2019, were used. Through preprocessing and visual interpretation, label data were generated to form a high-quality dataset containing 4 608 pairs of sample images. To address the inadequacy in the research of multi-scale internal solitary wave feature extraction, this paper proposes a multiscale internal solitary wave feature extraction model based on the Swin-Unet network to improve the extraction capability for internal solitary waves at different scales. The performance evaluation results show that, compared to the U-Net method, the proposed Swin-Unet model improved by 2.3% in F1 score, 2.44% in precision, and 12.12% in mean intersection over union (mIoU). The internal solitary wave extraction results at different scales in the Andaman Sea were subsequently analyzed, and the improved model was applied to Sentinel-1 full-track SAR imagery, verifying its applicability and robustness in complex marine regions. Experimental results demonstrate that the proposed model, based on the constructed dataset, can automatically extract ocean internal solitary wave features from SAR images.

With the continuous increase of global greenhouse gas concentrations and the escalating issue of climate warming, lidar based on the differential absorption coherent detection principle has become crucial for vertical profiles of greenhouse gas concentrations. To address the technical challenges in current ground-based CO₂ detection lidar systems of simultaneously achieving high integration, high precision, high range resolution, and long-term stability, this study developed a micro-pulse CO₂ profiling lidar operating at 1.57 μm with an all-fiber-integrated architecture. The system combines an injection-locked fiber laser and an off-axis reflective telescope in a coaxial transceiver design, realizing a compact system architecture(0.93 m × 0.34 m × 0.34 m) and sub-picometer wavelength stability (<0.6 pm under 10°C~40°C thermal variations). Horizontal detection experiments as well as continuous observation experiments were conducted. Experiments for horizontal detection revealed a significant linear relationship (R²=0.998) between the logarithmic ratio of dual-wavelength echo power and the detection range, confirming system precision; and the stability of the lidar system was verified by a continuous observation experiment.

Digital channelization has been widely applied in the field of electronic reconnaissance. The multi-phase structure of digital channelization can reduce data rates, making it easier to implement in FPGA. However, when the number of sub-channels is large, the data rate of each sub-channel will be significantly lower than the processing rate of FPGA, resulting in a waste of FPGA resources. In this paper, we introduce two-dimensional DFT into traditional DFT digital channelization structure and propose a channelization structure that matches the processing rate of FPGA, namely the digital channelization structure based on two-dimensional DFT. This structure is verified through simulation in Matlab(Matrix Laboratory)，and its computational complexity is analyzed and compared with that of traditional DFT-based digital channelization structure. Subsequently, the FPGA implementation block diagram and FPGA resource utilization are presented, and then the structure is tested on a hardware platform. The results show that the digital channelization structure based on two-dimensional DFT can correctly perform channelization of various signals. Compared with the traditional DFT-based digital channelization structure, it reduces computational complexity and significantly improves the efficiency of FPGA resources utilization, facilitating the FPGA implementation of large-scale digital channelization, which has certain engineering significance.

With the increasing number of space debris and the increasing complexity of spacecraft missions as well as the requirements for adaptability to extreme environments, the operational status, damage diagnosis, life prediction and reliable safety as-sessment of spacecraft structure are particularly important. Operating as an effective approach, spacecraft structural health monitoring obtains structural feature information through sensor systems deployed in the structure，analyzes and evaluates the structural status through algorithm processing, thereby ensuring the safe and stable operation of the spacecraft at all stages. This paper focuses on the key technologies of spacecraft structural health monitoring. Firstly, from the sensor end of information acquisition, the technical characteristics, application status, current problems and development directions of optical fiber sensing, acoustic emission sensing and surface acoustic wave sensing are reviewed. Then, the research progress of sensor deployment methods and diagnostic evaluation algorithms for information processing is introduced. Secondly, the development trends and main challenges of spacecraft structural health monitoring are summarized and prospected.

Micro capacitive pressure sensors have important application value in fields such as biomedicine, drone positioning, and wearable devices. This study focuses on MEMS capacitive gauge pressure sensors. A high-precision capacitive pressure sensor is designed and fabricated for implantable biomedical applications. This device is formed by anodic bonding between a glass substrate with fixed electrodes and an SOI wafer with elastic membranes. The elastic membrane will deform when the pressure on both sides changes, resulting in a change in the capacitance of the device. The readout circuit calculates the external pressure by detecting changes in capacitance. This paper improved the nonlinearity of capacitive pressure sensors by designing a structure of a boss on the membrane. The result from ANSYS finite element simulation shows that the nonlinearity was improved from about 17% (flat membrane) to 7% (with boss structure). The structure of the boss was formed by anisotropic etching of silicon with TMAH, and the SOI buried oxide layer serves as the stop layer of etching to achieve high device consistency. Finally, a packaging and testing platform is built for capacitive pressure sensors and calibration. In the measurement range of 0 ~ 40kPa relative to atmospheric pressure, this device achieved a testing accuracy of 0.30%, nonlinearity of 8%, and repeatability error as low as 0.09%.

In the field of ultra-high sound pressure noise environment of rocket engines, fiber laser microphones without diaphragm packaging have prominent pressure-resistant advantages. However, the phase noise problem introduced by unbalanced interferometer in engineering applications limits their performance. This paper focuses on the phase noise of the fiber laser microphone array introduced by the unbalanced interferometer in the modulation system. Firstly, the working principle of the modulation system and the source of the phase noise of the unbalanced interferometer are discussed, and a stable laser light source is incident on the unbalanced interferometer shared by the microphone system, to construct fiber laser microphone array system with suppressed optical phase noise. Then, the suppression principle is theoretically analyzed using the differential cross multiplying (DCM) demodulation. The noise information of the optical reference is used to cancel out the system noise introduced by the interferometer, thereby achieving the dynamic noise suppression. Finally, numerical simulation and experimental verification are conducted on the microphone array system. As a result, the phase noise measured in the non-equilibrium interferometer is reduced from approximately ± 0.34 rad to within ± 0.15 rad compared with the system without optical reference under field experimental conditions. The noise peak is sup-pressed by more than 7 dB, and the noise power spectral density is reduced from -25.02 dB/ to below -32.93 dB/. The suppression effect of phase noise is significant.

To meet the application requirements of inertial navigation, autonomous driving, and other fields, and to advance the development of micro-electromechanical systems (MEMS) silicon gyroscopes towards high precision, digitalization, and miniaturization, this paper presents the design and implementation of a MEMS silicon gyroscope interface ASIC with digital output, based on a 0.35 μm BCD process and a monolithic integration approach. A closed-loop drive scheme based on noise self-excitation is adopted, enabling the gyroscope to achieve harmonic vibration in the drive direction. The detection circuit uses a low-noise capacitive-to-voltage (C/V) conversion circuit to efficiently convert the small displacement signal into a voltage signal. Signal processing is performed using switched-capacitor phase-sensitive demodulation technology, combined with low-pass filtering, effectively suppressing noise interference and yielding a low-noise analog angular velocity output signal. To achieve the digital output of the silicon gyroscope's angular velocity, an integrated fourth-order feed-forward Sigma-Delta (ΣΔ) analog-to-digital converter (ADC) is designed to convert the analog angular velocity signal into a digital signal. The chip test results show that the dynamic range of the ΣΔ modulator reaches 110 dB, with a low-frequency noise floor of approximately -120 dB. The overall range of the gyroscope is ±200(°)/s, with a scale factor of 21 310 LSB/((°)/s), a nonlinearity of 178×10^-6, bias instability of 0.259(°)/h, and angle random walk of 0.028 7(°)/√h. The chip area is 4.3 mm×4.3 mm. By using the integrated interface ASIC to replace the traditional PCB-level system, the system's integration is significantly improved, successfully meeting the miniaturization requirements for MEMS silicon gyroscopes and promot-ing their development in high-precision digital applications.

Solid rocket motors are widely used in space launch vehicles, missile weapon propulsion, and spacecraft attitude and orbit control. Its tail flame temperature is a key parameter in evaluating propellant combustion performance and the engine efficiency. Due to the high temperature, high pressure and strong washout characteristics of the solid rocket motor exhaust flame, the test site environment is often accompanied by strong vibration, strong stray radiation, dust pollution and high noise, it's a challenge to temperature measurement techniques. In this paper, the development of contact and contactless temperature measurement techniques for solid rocket motor exhaust flame is summarized, and the advantages and disadvantages of the current techniques are analyzed. It is also pointed out that multispectral radiometric imaging thermometry and its temperature inversion algorithm are the current and future research frontiers.

Polymer Derived Ceramics (PDCs) thin-film thermocouples have the advantages of a simple preparation process and a stable high-temperature performance. They are very suitable for temperature measurement of hot-end components such as aircraft engine turbine blades. However, as the operating temperature of advanced engines increases, the upper limit of their temperature resistance needs to be improved. This article develops a precursor ceramic encapsulated PDCs: ITO/In₂O₃ thin film thermocouple. The encapsulation layer uses SiCN as the precursor solution and nano-Al₂O₃ powder as the filling material, and is prepared by the screen printing process. High-temperature test results show that the prepared sensor can survive at 1 500 °C in the short term and have stable output within 1 400 °C. The calibration test at 1 100 °C shows a linearity better than 0.999, with a multiple-cycle error of less than 1%.

The operating temperature of common acrylic-coated optical fibers is usually -65 °C to 80° C, and the working temperature of common high-temperature polyimide-coated optical fibers is up to 300 °C. At higher temperatures, metal-coated special optical fibers, such as aluminum-coated, copper-coated, and gold-coated fibers, are usually used for signal transmission. In this paper, the transmission loss of gold-coated fibers is tested at different ambient temperatures, and it is found that the transmission loss of gold-coated fibers varies greatly when the ambient temperature changes. For fiber optic temperature sensors based on the blackbody radiation principle, the error introduced by the variation in transmission loss can exceed 60 °C. On this basis, based on the transmission characteristics of light in different bands in gold-coated fibers, a dual-band correction method is proposed, which can correct the transmission loss of optical fibers caused by ambient temperature. After the correction, the error caused by the transmission loss is less than 15 °C.