Abstract:Terahertz communication has become a current research hotspot due to its extremely large bandwidth, and further improving the system capacity in terahertz systems has also become a problem worth exploring. This paper optimizes the terahertz system composed of all-electronic components using a hybrid Probability and Geometric Shaping(PGS) scheme. The Pairwise Optimization(PO) algorithm is employed to adjust the Probabilistically Shaped 16-ary Quadrature Amplitude Modulation(PS-16QAM) signal after probabilistic shaping to obtain the desired hybrid PGS-16QAM signal. By testing the optimization effects of PS-16QAM, Geometric Shaping(GS)-16QAM and PGS-16QAM on uniform 16QAM at different net rates, it is verified that the hybrid shaping has the best optimization effect. When the wireless transmission distance is set to 2 meters and the Normalized Generalized Mutual Information(NGMI) experimets have shown that threshold is set to 0.92, PGS-16QAM achieves a net transmission rate increase of 15.6%, 11.8%, and 3.8% compared to traditional 16QAM, PS-16QAM, and GS-16QAM, respectively.

Abstract:The demand for high-capacity, anti-interference, safe and reliable transmission between ships on the sea and between ships and aircraft is becoming urgent. Terahertz band has a high frequency band and large bandwidth, making it an excellent means of high-capacity transmission and anti-interference communication. Based on the characteristics of marine terahertz communication, the influence of water vapor attenuation on terahertz wave on the sea surface in China is analyzed firstly. Then, based on the link budget and propagation reliability calculation, a marine terahertz communication system is designed. After being tested on a 150 m river, the system's feasibility is verified by achieving a speed of 520 Mbps with an bit error rate of 2×10^-8.

Abstract:In order to meet the requirement of increasing transmission rate, the future communication technology will naturally develop to a higher carrier frequency, and terahertz communication technology becomes a possibility. Aiming at the I/Q imbalance problem in terahertz communication system under the background of large bandwidth, an I/Q imbalance damage model is constructed under terahertz zero-intermediate frequency architecture. The algorithm derivation and compensation architecture design are completed in corresponding narrowband and broadband scenarios, and the algorithm performance is improved by improving the cost function for broadband scenarios. The simulation results show that the Mean-Square Error(MSE) of the proposed algorithm is improved by 15 dB compared with that of the statistical algorithm. In the experiment of 220 GHz zero intermediate frequency communication system, the MSE of narrowband algorithm proposed in this paper is improved by 7 dB, and that of the broadband algorithm is improved by 1 dB.

Abstract:Traditional terahertz frequency doublers often utilize hybrid integrated circuits as implementation methods, leading to issues such as large size, high packaging loss, and poor stability. By employing an active device based on indium phosphide(InP) High Electron Mobility Transistors(HEMT) with a gate length of 2×25 μm, a fully monolithic integrated D-band frequency doubler is designed by using a combined simulation analysis method of Advanced Design System(ADS) and electromagnetic(EM) simulation. The frequency doubler is designed in the form of frequency doubling plus amplification, with the first stage being a frequency doubling circuit and the second stage using an amplification circuit. Within the range of 132~154 GHz, when the input power is 4.5 dBm, the output power is greater than 6 dBm, the fundamental wave suppression ratio is better than 31 dBc, the third harmonic suppression ratio is better than 36 dBc, and the maximum output power is 9 dBm@144 GHz, with a corresponding frequency conversion gain of 4.5 dB. The chip area of this frequency doubler is approximately 3.1 mm×1.3 mm. This design provides a new option for fully monolithic integrated terahertz sources and the realization of miniaturized terahertz sources.

Abstract:Terahertz waves occupy a unique position in the electromagnetic spectrum, characterized by high frequency, high bandwidth, and high penetration, which hold broad application prospects in fields such as communication, radar, imaging, sensing, and security inspection. Frequency converters like frequency multipliers and mixers are key components of solid-state terahertz systems. Schottky diodes boast low parasitic parameters, simple fabrication processes, and ease of integration, with their operating frequencies covering the entire terahertz band. Frequency conversion devices based on Schottky diodes, featuring room-temperature operation, broad bandwidth, electronic tunability, low phase noise, and high sensitivity, have become the mainstream devices in terahertz transceiver links. This article reviews the recent developments in Schottky diode technology, including its structure and fabrication methods. Additionally, it introduces the current state of frequency multipliers and mixers based on Schottky diodes and discusses future development trends.

Abstract:Terahertz communication is one of the important development directions for wireless mobile communication in the 6G era, characterized by large bandwidth and low latency, suitable for various application scenarios such as high-speed wireless backhaul and satellite communication. This paper designs a D-band (110~170 GHz) wireless communication system based on intermediate frequency synthesis, achieving D-band broadband wireless communication with a total bandwidth of (n×2) GHz by synthesizing n intermediate frequencies with a bandwidth of 2 GHz each, thereby achieving a transmission rate of over 100 Gbps. To verify the feasibility of the system, a 1/n scale-down verification was conducted on the designed n-path communication system. The results show that using a 2 GHz D-band channel bandwidth, a maximum of 11.2 Gbps air interface transmission rate and 9.4 Gbps service transmission rate can be achieved with 128-QAM(Quadrature Amplitude Modulation), proving that the n-path intermediate frequency synthesis system architecture using only one set of D-band RF front ends can achieve low-cost D-band broadband high-speed wireless communication.

Abstract:Pulse Current Injection(PCI) is an important means of studying the High-altitude Electromagnetic Pulse(HEMP) effects on electronic equipment. This paper designs a shortwave antenna port contact pulse current injection experimental platform, studies the effects of two different working states (receiving and transmitting) of shortwave equipment, as well as the impact of three different working frequencies (low, medium, and high) on the injected current. It also explores the performance differences of antenna port protectors in both stand-alone and online states, providing a reliable basis for subsequent performance tests of shortwave antenna port resistance to electromagnetic pulse interference.

Abstract:To address the issues of feed perturbation and reflector surface deformation in large radio telescope antennas caused by gravity, wind, and solar radiation, phased array feed technology is employed. By appropriately exciting each unit, the amplitude and phase errors resulting from feed perturbation and reflector surface deformation are compensated for. The performance of Gaussian feeds and phased array feeds under three different conditions is compared, and simulation results indicate that phased array feeds can not only correct the pointing deviation caused by feed perturbation but also compensate for the phase errors caused by reflector deformation, thereby enhancing the performance of the beam. Phased array feeds convert traditional mechanical surface adjustments to electronic surface compensation, which not only improves the performance of the antenna but also reduces resource consumption, making them suitable for large radio telescope antennas.

Abstract:A broadband two-dimensional scanning triangular grid multi-polarization transmission array has been designed, with the array antenna adopting a dual-polarized all-metal Vivaldi structure. The miniaturization of the metal Vivaldi antenna can meet the array conditions of the triangular grid. Based on the theory of polarization formation, the characteristics of its multi-polarization formation are studied to adapt to more diversified applications. The prototype measurement results indicate that the antenna array can achieve high-power multi-polarization formation within the X and Ku frequency bands (operating bandwidth ratio of 3:1); with an active Voltage Standing Wave Ratio(VSWR) less than 3, the azimuth and elevation scanning angles can reach ±30°; the equivalent radiated power (within ±30° scanning angle) can reach 110 kW; the array profile is 17 mm.

Abstract:Electrical Capacitance Tomography(ECT) image reconstruction algorithms utilize the sensitivity matrix as prior knowledge to invert the distribution of media within the pipeline, hence, the sensitivity matrix plays a crucial role in the quality of image reconstruction. Due to the soft-field characteristics of ECT sensors, the sensitivity distribution within the field is not uniform, with significant differences between the central and peripheral areas of the sensor, affecting the quality of the reconstructed images. This paper proposes a sensitivity preprocessing method based on the Sigmoid function. Simulation experimental results show that this method can significantly improve the uniformity of the sensitivity matrix and greatly enhance the quality of the reconstructed images: the Image Spatial Error(ISE) is reduced by 0.3825; the Relative Error(RE) is reduced by 0.386 5; and the Correlation Coefficient(CC) is increased by 0.0608, validating the feasibility of this method in ECT image reconstruction.

Abstract:In response to the need for target highlighting in infrared night vision aiming systems, a method for extracting target contours from infrared images is proposed. This method is based on real-time infrared imaging systems, and after analyzing the characteristics of infrared target images, the shortcomings of the application of Sobel operator in infrared images are improved through operations such as Gaussian filtering pre-processing, contrast enhancement, and dark background edge removal. The simulation has achieved accurate extraction of target edges in infrared images. The application effect of the algorithm in the infrared night vision aiming system is verified on a Field-Programmable Gate Array(FPGA) real-time processing platform. The results show that the method for extracting target contours in the infrared night vision aiming system has good edge extraction effects in the FPGA real-time system and has achieved significant target highlighting performance with less than 2% hardware resource occupation.

Abstract:The multi-level threats attribution in conventional Internet of Things(IoT) environments is mainly achieved through the classification of network data relationships, which overlooks the similarity between conventional data and threat data, leading to a large number of false positives in the attribution results. In response to this, a multi-level threats attribution method for IoT environments based on deep learning and genetic algorithms is proposed. A deep learning neural network is established to identify threat data in the IoT environment, and batch normalization operations are added to separate conventional data from threat data, extracting features of multi-level threats data. Genetic algorithms are applied to obtain the optimal individual, achieving the initial node attribution and positioning of threat data. Experimental results show that the attribution results obtained using the proposed method have fewer false positives and are more accurate, meeting the practical needs for the security maintenance of IoT environments.

Abstract:In response to the current issue of low accuracy in sentiment polarity analysis of short texts in power consulting, this paper proposes an improved Latent Dirichlet Allocation (LDA) algorithm-based classification algorithm for power user consulting texts. Based on the analysis of the relationship between power consulting short texts and sentiment, concepts such as sentiment word co-occurrence bags, topic-specific words, and topic relationship words are defined. To improve the quality of semantic analysis, an execution process for the improved LDA algorithm for classifying power user consulting texts is designed. Experiments show that the proposed model demonstrates excellent performance, with an average precision of 90.91% and an average recall rate of 85.03%. The proposed model can fully leverage the advantages of multi-model integration, effectively enhancing the model performance.

Abstract:To address issues such as congestion, latency, high packet loss, and low throughput in the data transmission of electricity information acquisition terminals, and to improve cache utilization and data transmission efficiency, a dual-queue cache optimization algorithm for electricity information acquisition terminals based on time series is proposed. Preliminary statistics are conducted on the time series information of user electricity consumption, and electricity consumption trends and anomaly detection results are extracted as upload data. A Dual-Buffer Queue Management based on Priority(DBQM-P) dual-cache optimization algorithm is constructed, which divides queues according to the priority of different services and calculates the optimal discard probability. Different packet discard strategies are implemented in the dual-queue cache model to achieve efficient transmission of electricity information acquisition terminal data. Experiments show that this method can collect user time series information, cache data according to the priority of services, and upload it to the electricity information acquisition system background for display, significantly improving the cache utilization of electricity information acquisition terminals, increasing the amount of data transmitted per unit of time, with the highest packet loss rate being only 0.58%, reducing data loss, ensuring the transmission of urgent and important business information, and enhancing the real-time and reliability of data transmission.

Abstract:To investigate the issue of reduced electron multiplication factor in Complementary Metal Oxide Semiconductor(CMOS) image sensors with an aluminum oxide passivation layer structure after being bombarded with high current density electrons, this paper simulates the fabrication process of CMOS image sensors with an aluminum oxide passivation layer. An aluminum oxide passivation layer is prepared on the surface of P-type silicon with a crystal orientation of (100) and a doping concentration of 5×10¹⁸ cm^-3. The conditions for electron beam bombardment of CMOS image sensors are simulated, and the prepared P-type silicon samples are bombarded. A high-frequency C-U testing device is employed to test the high-frequency C-U curves of the samples before and after bombardment. Based on the test data and analysis using the Shockley-Read-Hall(SRH) theory and minority carrier transport equations, it is concluded that the internal positive charge deposition in the passivation layer and the increase in defect state density at the silicon interface caused by electron bombardment are the intrinsic reasons for the reduction in the electron multiplication factor of this type of image sensor.

Abstract:The confusion characteristic of masking technology can increase the difficulty of attackers to analyze the logic value of the circuit, and the combination of masking technology and Dual-Rail Precharge(DRP) technology can further play a role in resisting power analysis attacks. The application of masking technology and dual-rail precharge technology requires corresponding processing of the input signals and output signals. Based on this, this paper proposes a single rail to dual-rail conversion logic circuit, which can realize the conversion of signal. Then a mask logic conversion circuit is proposed, which can realize the conversion of the output value of the circuit according to the mask value. At last, a single-dual rail mask logic structure is proposed to form a circuit design scheme with power attack resistance. The above logic circuits have been verified by Hspice simulation and have correct logic functions, which provides a way for the circuit design against power analysis attacks.