Terahertz(THz) Surface Plasmons Polaritons(SPPs) can mimic optical Surface Plasmons (SPs) and obtain similar optical properties with periodic sub-wavelength structures, which typically consist of propagating SPPs and Localized Surface Plasmons(LSPs). In this work, graphene is utilized as the active stimuli to dynamically control the amplitude, frequency, and phase of SPPs and reconfigure the resonant modes of LSPs at various bias voltages. Such design provides new solutions for active control of SPPs and LSPs at THz frequencies.

The scattering and absorption of raindrops will seriously increase the transmission loss of terahertz waves in the earth-space links and reduce the performance of wireless communications. In order to realize the transmission application of terahertz waves in the earth-space links, it is necessary to deeply study the transmission characteristics of terahertz waves in the rainfall environment. In this paper, the original rain attenuation model is further modified, and the influence of rainfall rate on terahertz wave transmission over the earth-space links is analyzed based on Mie theory. The calculation results are compared with that of the original model, and it shows that, in the whole terahertz bands, the rain attenuation loss increases with the increase of rainfall rate, and increases first and then decreases with the increase of frequency. There exists less rain attenuation loss in the high-frequency terahertz bands than in 0.1~1 THz bands. When the frequency exceeds 1 THz, the closer the atmospheric window is to 10 THz, the smaller the loss will be, and it will have more advantages in wireless communication transmission in rainy weather environment. The lower the frequency, the greater the zenith angle, and the difference of the rain attenuation model before and after modification will be more obvious.

The special-shaped surface components are widely used in aviation, aerospace, shipbuilding and other fields, and their bonding quality has become an important factor affecting work safety. With its unique physical characteristics, terahertz technology is almost the only means to detect the bonding quality of Polymethaerylimide(PMI) materials. The curvatures of the upper and lower surfaces of the special-shaped surface components are inconsistent, which makes it impossible to accurately judge the bonding quality of the special-shaped surface components when only the upper surface is used as the reference surface for path planning. To tackle this problem, metal sheets of different shapes on the lower surface are fixed to simulate the defects in the bonding layer. Taking the upper and lower surfaces of the special-shaped curved surface components as the benchmark surfaces respectively, the robotic terahertz time-domain spectrum detection system is employed for detection. The terahertz imaging results of the two detection methods are compared and analyzed. The results show that when the lower surface is used as the benchmark surface for detection, the signal to noise ratios at area II and III are improved by 12.09 dB and 10.39 dB than that when the upper surface is the benchmark surface; the ratios of the actual detection area to the theoretical area of the metal sheet at area II and III are improved by 55.97% and 80.81% than that when the upper surface is used as the benchmark surface for detection. This better meets the detection requirements of special-shaped curved surface components. This work will promote the application of terahertz imaging in practice and provide a basis for further research in related fields.

To address the problem of insufficient precision of existing single-satellite positioning techniques, a direct positioning method of interference source for satellite navigation system based on propagation operator is proposed. Firstly, the received signal of the satellite is modeled and the covariance matrix at each moment is calculated. After blocking the covariance matrix, the propagation operator is obtained to estimate the orthogonal projection subspace of the steering vector. Then the loss function can be established and the position of the interference source can be estimated by searching the loss function. Theoretical analysis and simulation results prove that the localization accuracy of the proposed method is comparable to that of the traditional Multiple Signal Classification(MUSIC) -based direct positioning algorithm, while the calculation complexity is greatly reduced. Meanwhile, the localization accuracy is much higher than that of the existing bearing-only localization techniques, which is valuable for practical engineering applications.

Computational time in indoor Ray Tracing(RT) would rise sharply if more reflections are considered. The upper limit value of reflection number is the key to the efficiency of indoor RT. However, the convergence of reflection in indoor RT has not been clearly discussed yet. A convergence analysis of RT based on statistically studying digital data of indoor scenario is presented aiming to obtain the appropriate upper limit value of reflection number to improve the efficiency of RT without losing accuracy. Convergence study focuses on the distribution of indoor scene, derives the probabilities and the power of different reflection paths, and finally finds out the convergence result of the power of receiver and the upper limit value of reflection number. The comparisons with RT simulation show that the convergence of this model is consistent with that of RT simulation under the same computational accuracy and this study is feasible to improve the efficiency of RT.

Power line carrier communication is a new effective communication method for a wide range of Device to Device(D2D) data exchange and communication applications, which bears the advantages of free deployment and easy direct connection. However, due to the communication congestion or electric power interference, different kinds of failures are often caused in the actual system. An efficient recovery mechanism is necessary to ensure reliable data transmission. By introducing Multi-Protocol Label Switching(MPLS) technology, a novel power line carrier communication distinguishable fault recovery algorithm, Diff-RECV, is proposed. While considering different survivability Quality of Service(QoS) requirements, by combining protection and recovery mechanism with multipath recovery mechanism, differentiated traffic protection and recovery are realized. The proposed Diff-RECV algorithm is verified by experiments. The results show that it can not only recover 100% traffic, but also has higher recovery speed than spread method.

Power line carrier communication technology utilizes existing power transmission networks for data transmission, which has the characteristics of low construction cost, fast and flexible deployment, and is widely used in local communication in local area networks. However, when the number of nodes is too large or the acquisition frequency is too high, each node will transmit data to the root node alone, which will bring huge amount of data to the entire communication system, and reduce the communication efficiency, affecting the real-time monitoring of the photovoltaic system. For this reason, aiming at the huge amount of data generated in the process of power line carrier communication, a data fusion algorithm of power line carrier communication based on minimum spanning tree transmission path is proposed to reduce the amount of transmission data and save the communication transmission resources, thus enhancing the transmission capacity of power line carrier access network. Finally, the proposed algorithm is proved to be effective by comparing the amount of data brought about by the fusion algorithm and the non-fusion algorithm.

A broadband high-gain low-profile antenna based on gradient size metasurface is proposed. The antenna is composed of a double-layer metasurface and a layer of microstrip slot. The double-layer metasurface is composed of gradient size hexagonal array patches printed on two dielectric plates respectively. There are non-equidistant gaps between these patches. This gradient design of the metasurface unit size can generate multiple adjacent resonance points to broaden the bandwidth. The antenna's bandwidth radiation characteristics are analyzed by changing the size and structure of the metasurface antenna. In order to obtain the best broadband performance, genetic algorithms are employed to optimize the antenna geometric parameters. To verify the simulation results, a sample antenna with a side length of 43.3 mm and a thickness of 4.853 mm is fabricated and tested. The actual measurement results show that the -10 dB impedance bandwidth of the antenna reaches 54% (3.99~6.93 GHz), the highest gain reaches 12.05 dB, and the gain remains above 8 dB in 4~6 GHz range. Therefore, the antenna realizes the characteristics of wide frequency band, high gain and low profile, and can be applied to many fields of wireless communication.

Breast cancer is the first malignant tumor in women worldwide. Studying on breast cancer diagnosis and prediction methods based on neural network models is to combine clinical and machine learning to help medical workers more quickly and accurately determine the disease or not, and solve the problems of over-fitting, missed diagnosis rate and high misdiagnosis rate in existing models, and improve the accuracy of prediction models. The University of California Irvine(UCI) data set contains 669 samples, including 357 benign samples and 212 malignant tumor samples, a total of 10 features to train the prediction model. The 10 neural network models are combined through Adaboost method, that is, multiple weak classifiers are combined by Adaboost algorithm to form a strong classifier. The final output is an integrated prediction model with higher accuracy, stronger self-learning ability, adaptive ability and excellent generalization performance. The conclusion shows that the prediction accuracy of the model is 98.550 7%, and the Accuracy(AUC) is 0.996 6, which indicates that the established model is very stable, and has good discrimination and good verification effects. It provides further technical support and guarantee for clinical application.

Digital terrestrial Television Multimedia Broadcasting-Advanced(DTMB-A), is a new type of illuminator of opportunity for passive radars, which has broad bandwidth and excellent adaptability against multipath effect. In this paper, DTMB-A signal Ambiguity Function(AF) is concluded and the mechanism of intra-frame and inter-frame ambiguity peaks is researched by theoretical derivation and simulation verification. The analysis shows that the period deterministic frame structure(the synchronization channel and guard interval) is the main factor that causes the ambiguity sub-peaks. Therefore, a DTMB-A signal ambiguity functions suppression method is proposed by using non-uniform sampling, which has low computational complexity and is convenient for parallel computing. Simulation results show that this method can suppress DTMB-A signal Ambiguity Functions into almost ideal thumbtack shape effectively, which is the foundation of detecting target on DTMB-A passive radar.

Aiming at the problem of noise reduction of gas leakage acoustic signals, a method combining ensemble Wavelet Packet Analysis(WPA) and Variational Mode Decomposition(VMD) was proposed to de-noise the collected gas leakage acoustic signals. Firstly, the wavelet packet transform is employed to preprocess the noise of the signal. Then, the de-noised signal was decomposed by VMD to obtain all the Intrinsic Mode Function(IMF) components, and the effective IMF was judged according to the correlation coefficient criterion. Finally, the active components were extracted and the signal was reconstructed. The experimental results show that the above method can effectively eliminate all kinds of noises contained in the gas leakage signal. After noise reduction, the SNR is 15.485 1, and the root mean square error is 0.028, which reduces the interference for the subsequent signal analysis. The above method provides a new idea for the feature extraction and analysis of gas leakage acoustic signal.

In view of the problem of low computational efficiency in multi-mode Synthetic Aperture Radar(SAR) imaging processing, a parallel acceleration method is proposed for multi-mode SAR imaging based on Graphic Processing Unit(GPU). In order to make full use of GPU's memory resources and improve the efficiency of the algorithm, in the parallel computing part of the algorithm, the large-scale data parallel is carried out in the matrix transposition and matrix multiplication by using shared memory. The experimental results show that the algorithm greatly improves the efficiency of multi-mode SAR imaging, and the maximum acceleration ratio reaches 55.62, which solves the problem of low utilization of GPU.

There is an urgent need for an online monitoring system that is of trace-level measurement, fast response, precise positioning and being easy to install, because it is difficult to measure small leaks in irregular, complex and narrow spaces. An online monitoring system is designed in this paper. The total node uses XC6SLX16-3CSG324I as the main control chip, and the child nodes use STM32F103C8T6 as the main control chip in the hardware circuit. Microelectro Mechanical Systems (MEMS) metal oxide sensors Ccs811, Bmp180, and Si7021 constitute the data acquisition circuit which adopts flexible circuits technology to adapt to small space placement and easy monitoring. The tested leaking working fluid can be pure gas or liquid working fluid containing some volatile substances. Experimental results show that the system can achieve non-contact measurement, fast sensing, and precise positioning. And the gas concentration of Volatile Organic Compounds(VOC) can be measured below 100 ppb, realizing the trace level measurement.

Considering the limited storage, computing, and communication resources of smart terminals of the power Internet of Things, most of the existing operation management algorithms focus on reducing power consumption of nodes, which limits the security and anti-capture performance of terminals. For ensuring the performance of terminal nodes in the power Internet of Things, while improving the ability to resist physical capture attack, a lightweight key management scheme is proposed. Firstly, the central control area is increased through the deployment of concentrator nodes, forming a new two-tier grid deployment model. Then based on the new structure, a two-stage key information distribution algorithm is proposed. In each stage, the security threshold of the Blom matrix space is set according to the number of nodes in each sub-area, and greatly improves the connectivity and anti-capture performance of the cyber network. The simulation proves that when the proportion of captured terminals is 5.5%, the failure probability of communication link in the proposed scheme can be reduced by 63% and 68%, respectively, compared with those of the t-UKP scheme and the SPECC scheme.

Based on the 0.25 μm SiC substrate GaN High Electron Mobility Transistor(HEMT) process, the final power device size is selected and its optimal impedance is determined by the Gmax and the unit output power density of the active device. The tertiary amplifier is adopted, and its gate width ratio is 1:4:16 to achieve high power gain and high efficiency. By using the equal-Q-matching technique, and integraing the bias circuit into the matching circuit, an impedance transformation is realized with simple, low loss and broadband. With the help of the extraction of parasitic parameters in electromagnetic fields, the compact chip is realized. The chip size of the Monolithic Microwave Integrated Circuit(MMIC) amplifier is 2.8 mm×2.0 mm. The test results show that in the 2~6 GHz frequency range, and under the conditions of the drain voltage of 28 V, the gate voltage -2.2 V, and continuous wave, the large signal gain of the MMIC amplifier is greater than 24 dB, the saturation output power is greater than 43 dBm, and the Power Additional Efficiency(PAE) is greater than 45%. The proposed paver amplifier can be widely used in electronic countermeasures and electronic fence.

The Digital Low Drop-Out(DLDO) regulators are widely used because it can operate at low supply voltage. In the DLDO regulators, the Analog-Digital-Converter and shift register are employed to regulate the voltage. However, when the load has a transient voltage change, it will be stabilized for a long time. In addition, in the PI control system, the circuit with a large integral coefficient has a short setup time, but overshoot will occur before the output is stable. Although the output of the model with a small integration coefficient can be directly stabilized, the setup time is too long. A high-speed adjustable circuit model is proposed, using a voltage sensor and a Time Digital Converter(TDC), and adding two kinds of integrators with different integral coefficients into the circuit. Firstly, the voltage sensor and Time Digital Conversion Technology(TDCT) are utilized to realize the analog-to-digital conversion to obtain the digital signal. When judging the error of digital signal compared with the reference voltage to be large, the control circuit chooses large integral coefficient to output to PI control. When the error is small, the control circuit chooses small integral coefficient, so that the circuit can combine the advantages of the circuits with different integral coefficients to shorten the circuit setup time and the stabilization time at the same time.耿嘉荣(1997-), 女, 硕士, 工程师, 主要研究方向为超大规模模拟集成电路设计.张洪达(1997-), 男, 硕士, 工程师, 主要研究方向为超大规模模拟集成电路设计.陈志杰(1986-), 男, 博士, 副教授, 主要研究方向为超大规模模拟集成电路设计.