Abstract:As electronic technology advances towards higher integration and miniaturization, three-dimensional circuit layouts have become increasingly prevalent, making the effective transmission of millimeter-wave signals between the surface and internal circuits particularly critical. This study presents a novel design for an ultra-wideband, low-loss vertical interconnect structure transitioning from a stripline to a Grounded Coplanar Waveguide(GCPW), aimimg at addressing signal reflection and radiation issues caused by parasitic inductance and capacitance in interconnect structures. Through the analysis of an equivalent circuit model and preliminary parameter design, combined with optimization using three-dimensional field simulation, the final design parameters were determined. The interconnect structure employs a 0.2 mm diameter via for connection and features an isolation ring with a mere 0.8 mm diameter, ensuring the simplicity and ease of fabrication of the structure. Simulation results indicate that the design achieves broadband coverage from DC to 80 GHz, with S₁₁ less than -13 dB and S₂₁ greater than -0.4 dB, demonstrating excellent performance. To interface with the testing system, a test board was designed to convert to a coaxial connector, extending the operating frequency to 40 GHz. Actual test results show that, within the DC to 40 GHz range, return loss is less than 11 dB and insertion loss is less than 0.4 dB, further verifying the effectiveness and practicality of the design.

Abstract:Single-pixel imaging is a novel computational imaging technique that uses only a single-pixel detector to acquire the image of an object with the help of spatial light modulation. In the terahertz band, to overcome the problem of scarcity of array detectors and realize sub-wavelength imaging in near-field modulation, a continuous terahertz single-pixel subwavelength imaging system is presented based on an optically pumped silicon wafer all optical modulator with a spatial resolution of λ/7.62. The imaging results on the resolution test chart show that when the imaging details are not of particular interest, thick silicon wafers can be employed to obtain large modulation depths, and the compressive reconstruction algorithm can be adopted to suppress noise and smooth the output images. To pursue higher imaging spatial resolution, thin silicon wafers are needed to reduce the crosstalk between modulation units, and the correlation reconstruction algorithm is employed to retain more image details. This study provides a concise reference for terahertz subwavelength imaging.

Abstract:Terahertz photothermoelectric detectors are based on the principle of thermogenerated carriers migrating under the influence of a temperature gradient to achieve terahertz wave detection. They have advantages such as fast response, ultra-wideband, self-powered, room temperature operation, and simple structure, which have attracted widespread attention. Currently, the readout of detectors mainly adopts a modulation-demodulation method, realized by cascading a current amplifier with a lock-in amplifier for measurement, which has low integration, high cost, and is difficult to achieve array readout. To meet the application requirements of spectral measurement and imaging perception, this paper studies the readout method of the photothermoelectric array detector unit. Starting from the detector mechanism, the output signal is modeled and analyzed; based on this, a board-level dedicated readout circuit is designed to achieve front-end amplification and lock-in amplification functions. Tests show that this method can achieve high-precision readout of terahertz photothermoelectric detectors in a strong noise background environment, with a gain of 140.7 dB, and the signal-to-noise ratio is improved by 38.3 dB.

Abstract:Metasurfaces are artificial surfaces composed of sub-wavelength unit structures, demonstrating tremendous potential for manipulating electromagnetic waves. Catenary electromagnetics provides new ideas and methods for the design of metasurfaces. This paper proposes a multifunctional dichroic metasurface based on a catenary structure, capable of selectively absorbing electromagnetic waves in different directions. Simulation results show that the device can achieve 92% Linear Dichroism (LD) and 96% Circular Dichroism(CD) in the infrared region. Both functions can be realized simultaneously by merely changing the incident direction of the electromagnetic waves, and both functions have high efficiency within a certain range of incident angles. In addition, the influence of different geometric parameters on the absorption performance is analyzed, as well as the physical mechanisms for selective absorption of different electromagnetic waves. This metasurface has the advantages of simple structure, easy integration, and a wide range of applications, and has potential application prospects in the fields of imaging, sensing, and spectroscopy.

Abstract:Based on a flexible twisted bilayer chiral metasurface sensor, utilizing terahertz time-domain spectroscopy technology, with chiral Lactic Acid(LA) enantiomers as the research subjects, a method for sensing the concentration of chiral substances and enantiomer recognition in the terahertz band is proposed. The results show that the Transmission Circular Dichroism(TCD) of the chiral metasurface sensor shifts with the increase of concentration, and the shift amounts are different for different chiral enantiomers. The highest detection sensitivity for Levorotatory Lactic Acid(L-LA) and Dextrorotatory Lactic Acid(D-LA) are 2.6 GHz/(mg/mL) and 1.9 GHz/(mg/mL), respectively, with a detection limit as low as 0.01 mg/mL. The great potential of the chiral metasurface sensor in LA sensing and chiral recognition provides an efficient, low-cost technical method for the sensitive detection of chiral enantiomers.

Abstract:A pixel-level digital focal plane readout circuit was designed to overcome the charge capacity limitations of traditional analog readout circuit technology, enabling a larger dynamic range and lower noise digital image readout. Additionally, digital image processing is performed internally at the pixel level, enabling functions such as Non-Uniformity Correction(NUC), dead pixel compensation, digital Time-Delay Integration(TDI), and spatial filtering for image preprocessing. The circuit was fabricated using a 40 nm CMOS process with an array specification of 640×512, a pixel pitch of 30 μm, and the overall chip size is approximately 22 mm×19 mm. Test results indicate that the circuit can significantly reduce(by approximately 90% and 63%, respectively) the spatial noise in the output image through TDI and spatial filtering functions, thereby enhancing the image quality.

Abstract:High-performance wide-spectrum upconversion imaging devices play an important role in fields such as medical care, food safety, non-destructive testing, and national security. However, existing semiconductor upconversion devices are limited by their narrow detection range and low upconversion efficiency. In order to achieve a wider spectrum and efficient upconversion, this study significantly improves the performance of the ratchet upconversion device by optimizing the LED structure. The improved LED's electroluminescence efficiency has been increased by two orders of magnitude. It can turn on light at a driving current of μA level, and its electroluminescence spectrum is closer to the theoretical regular Lorentz line. The overall surface luminescence uniformity of the device is also significantly improved. The research clarifies the performance optimization principles and provides a reference for future improvements in upconversion devices.

Abstract:Based on the fundamental principles of quasi-optical and Gaussian beams, research has been conducted on quasi-optical reflectors and lenses, leading to the design of a quasi-optical feed system for millimeter-wave and submillimeter-wave antennas. This system is capable of simultaneously receiving electromagnetic radiation signals in the 89~115 GHz and 176~183 GHz frequency bands through two optical paths. Elliptical reflectors and lenses are utilized to focus the beams and control the system's structural envelope. Polarization grid networks are employed to separate channels, and calculations and preliminary analysis of dual-channel performance are conducted. The system operates in a low-temperature environment, and in response to practical requirements and cold optical analysis, constraints are proposed and optimized for the spatial position and beam radius of quasi-optical components. Theoretical calculations and simulation results indicate that the system meets the design requirements for cold optics and quasi-optics.

Abstract:In response to the current intelligent anti-jamming technology's poor performance against rapidly changing interference, a new type of intelligent anti-jamming technology combined with priori knowledge networks is proposed. Firstly, a priori knowledge network is constructed to predict the interference information of the next moment based on historical interference information, enabling the system to better cope with rapidly changing interference; then, reinforcement learning algorithms are employed to achieve online learning of new interference patterns, allowing the algorithm to be applicable to scenarios where the dynamic changes of interference exceed the adaptation range of offline learning models. The simulation comparison between the proposed algorithm and the reinforcement learning algorithm without prior knowledge shows that the proposed algorithm has higher decision accuracy and faster convergence speed when facing rapidly changing interference, and has better adaptability to the environment, which can effectively carry out intelligent anti-jamming.

Abstract:Aiming at the problem of jamming suppression in distributed radars, a joint polarization-spatial-temporal domain processing method is proposed for compound jamming in distributed radars. Firstly, a distributed polarization array radar system model of single-transmitter multiple-receiver is established. Secondly, the received signal is reconstructed into a third-order tensor according to its polarization-spatial-temporal characteristics. Furthermore, tensor decomposition is employed to separate the target echo from jamming signals, so as to realize the suppression of blanket jamming and smart jamming. Then, by using the uniqueness of the position and velocity information of the real target, the deception jamming is suppressed by joint positioning of multiple sites, while the position coordinates and velocity vectors of the target are estimated in the meantime. Finally, the effectiveness of the proposed algorithm is verified by numerical simulation experiments.

Abstract:Under the influence of earth curvature, the localization error of traditional positioning model based on rectangular plane coordinate system will increase significantly with the detection range increasing, and it seriously affects the positioning and tracking accuracy of long-range targets. This paper proposes a positioning method with single moving platform based on spherical models. It transforms the plane rectangular function equation into the spherical trigonometric function equation to reduce the influence of the earth curvature error. It utilizes the Unscented Kalman Filter(UKF) algorithm to solve the complicated nonlinear observation equation iteratively and realizes high-precision position estimation of long-range targets. Simulation results demonstrate that the proposed method based on spherical models has a higher position accuracy which is increased by 0.3%R~0.6%R.

Abstract:For the application of the Multiple Signal Classification (MUSIC) algorithm with super-resolution capabilities in the direction finding of passive radar seeker heads based on conformal polarization-sensitive arrays, the definition of spectral function angular resolution and the discrimination angle threshold are proposed. By approximating the expected value under the asymptotically biased condition using the definition of the MUSIC algorithm's zero spectrum, the corresponding angular resolution expressions for vector array and scalar array models are derived respectively. Taking the uniform circular array as an example, the influence of various parameters on angular resolution is quantitatively analyzed based on the computer simulation model, and the statistical values of the discrimination angle threshold for scalar and vector arrays are compared. Simulation results show that under the same array and signal source parameter settings, the discrimination angle value of the scalar uniform circular array is generally higher than that of the vector uniform circular array.

Abstract:In recent years, thanks to the enhancement of computing power of computers and the vast amount of data generated by the internet, Deep Learning(DL) technology has achieved rapid development. Among them, the most notable Convolutional Neural Networks(CNN) have successfully been commercialized in fields such as image recognition,object detection, and natural language processing. However, as the network layers become deeper, the demand for computing power and memory has risen sharply. How to accelerate convolutional neural networks and deploy them on hardware accelerators has gradually become a hot topic in academic research. Starting from the advantages of developing neural networks with Field-Programmable Gate Arrays(FPGA), various development methods of FPGA are introduced, various optimization strategies for deploying and accelerating convolutional neural networks are discussed in detail, and the performance of FPGA convolutional neural network accelerators using different optimization strategies is presented. Finally, the future development direction of FPGA convolutional neural network accelerators is expected.

Abstract:In view of the problems of long data migration, high maximum occupancy rate of storage space, high error rate of transfer learning and low online probability of visited data, the historical data migration technology of domestic database based on domestic Central Processing Unit(CPU) environment is studied. Firstly, the system software and hardware are clustered and deployed in the domestic CPU environment to improve the migration rate of historical data between domestic databases. Secondly, an isolation forest model is established, and the historical data is input into the isolation forest model for trend prediction, thereby eliminating the abnormal data in the domestic database, and reducing the amount of data to be migrated. Finally, a data migration model is constructed, and an alternating optimization strategy is adopted to find the optimal solution of the model, thus completing the migration of historical data in domestic databases. The experimental results show that the data migration time of this method is 18 minutes, and the maximum occupancy rate of storage space is between 10% and 25%, the ALC(Area under the Learning Curve) index value is 0.78~0.95, and the online probability of the accessed data can always be maintained at more than 97%, proving that this method has a short data migration time, a low maximum occupancy rate of storage space, a low error rate of migration learning, and high access efficiency, demonstrating good application effects.

Abstract:A low-g-value magnetic self-locking Micro-Electro-Mechanical Systems(MEMS) inertial switch with a threshold of 5g, featuring adjustable threshold and self-recovery capabilities, has been designed. The inertia sensitive unit of this inertial switch consists of a square mass block, a square chessboard-shaped magnet fixed beneath the mass block, and four square Archimedean spiral beams supporting it. The magnet, along with four ferromagnetic fixed electrodes located beneath the moving electrodes and a double-layer planar coil, jointly achieve the functions of magnetic self-locking and threshold adjustment. Simulation analysis is conducted using the finite element simulation software ANSYS. The prototype is manufactured by using laser processing and PCB technology, and the performance of the sample is tested by using a centrifuge. The test results show that the fabricated MEMS inertial switch has a threshold acceleration of 5.27g in the vertical sensitive direction. By applying a current in the range of -0.5 to 0.5 A, the threshold adjustment range is from 6g to 3.75g. The results indicate that this structure can achieve the locking function while enabling self-recovery without external force and allowing threshold adjustment within a certain range.

Abstract:To obtain the high-voltage high-repetition-rate pulse output with a half-width of about 10 ns required for plasma research, two sets of high-voltage switch modules composed of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) switches in series are used. By combining traditional capacitor energy storage pulse generation circuits with pulse tail cutting circuits, narrow pulses are generated. Based on the actual working requirements of the switches, adaptive design and simulation optimization of the narrow pulse generation circuit are carried out; according to the optimization results, an experimental device for narrow pulse generation circuit is built. After testing, a pulse output with a peak voltage about 10 kV, a half-width about 10 ns, and a front edge about 6 ns is obtained on a load of 500 Ω.

Abstract:Variations in space environment temperatures can have distinct effects on the level of charging on dielectric materials surfaces of spacecraft. To address this, a numerical model has been established in this paper based on the current balance equation to study the impact of temperature on the surface charging of polyimide. Subsequently, utilizing a spacecraft material surface charging simulation experiment system, the influence of temperature changes on the surface charging characteristics of polyimide under electron irradiation is investigated. The simulation results indicate that when the temperature is fixed, the surface charging equilibrium potential of polyimide increases as the beam current density increases at levels of 0.5 nA/cm², 1 nA/cm², and 2 nA/cm². Conversely, when the beam current density is held constant, the surface charging equilibrium potential of polyimide decreases with the rise in temperature within the range of 243 K to 363 K. The larger the beam current density, the less significant the effect of temperature changes on the equilibrium potential. This research finding can serve as a reference for the charging protection of dielectric materials on spacecraft in response to temperature variations.