This paper gives an overview to the fundamental principles, key components, system design and technical advantages of quasi-optical technology, particularly for its applications in the millimeter and terahertz systems in fields of remote sensing, radioastronomy, and imaging. A perspective to the state-of-the-art and future development of quasi-optical technology has been given. Quasi-optical technology is a set of system design and analysis techniques based on Gaussian beam propagation in free space. Systems based on quasi-optical technology bears advantages of high-power handling capability, multi-polarization, low transmission loss, and high compactness. In the future, quasi-optical technology will be seeking more applications in these areas and further development can be highly envisaged.

Detecting and studying the atmospheric wind field is one of the most important means of understanding the structure of the middle and upper atmosphere, among which meteor radar is a very good means of observing the atmospheric wind field. In order to better understand the characteristics of the atmospheric wind field in the mid-latitude Mesosphere and Lower Thermosphere(MLT) region, this paper uses the 2016 Beijing Meteor Radar inverted wind field data for research. Firstly, the change characteristics of the atmospheric mean wind field with time and height are studied, it is concluded that the zonal wind in the MLT area over Beijing from January to March is dominated by west wind, and for the meridional wind, south wind and north wind alternate significantly, but the north wind is still dominant. And then the atmospheric tidal wave at 90 km is studied. The law of atmospheric tide changes with time is obtained through the Lomb-Scargle power spectrum method and harmonic fitting. We found that the influence of tidal waves on the atmospheric horizontal wind field in the mid-latitude is mainly the half-day tide, followed by the day tide.

Non-Orthogonal Multiple Access(NOMA) is introduced into massive Multiple Input Multiple Output(MIMO) system in order to further improve the spectrum efficiency. Nevertheless, when the channel between the base station and the user is poor, it is difficult to guarantee the spectrum efficiency of the user. A massive MIMO-NOMA system based on Intelligent Reflecting Surface(IRS) is discussed to deal with this problem. An IRS-assisted massive MIMO-NOMA system model is considered firstly. Then according to the cluster head selection algorithm, a cluster head is selected for each beam to design analog precoding. Users are grouped according to the correlation of equivalent channels, and the user with the strongest equivalent channel gain in each beam is selected to design digital precoding. Finally, the power allocation of the base station and the phase shift matrix of the IRS are jointly optimized to ensure the fairness of the user’s spectral efficiency, that is, to maximize the minimum spectral efficiency. The simulation results show that compared with the massive MIMO-NOMA system without IRS, the IRS-assisted massive MIMO-NOMA system can significantly improve the spectrum efficiency of the weakest user.

At present, Ku-band satellites are mainly adopted in fire protection in Guangdong province. However, the frequency resources of Ku-band satellite are tight and the link bandwidth is low. Therefore, when the disaster occurs, the information that the rear command and command center can obtain from the front is very limited, and there is no extra bandwidth for other emergency communication equipment on the front line. The problems and requirements of the current firefighting satellite system are analyzed, and the high-throughput Ka-band satellite communication system is proposed to put on use, which can effectively solve the problem of low bandwidth and limited transmission of information resources in the current firefighting satellite system.

The rapid development of Unmanned Aerial Vehicle(UAV) based communication technology and the rapid growth of intelligent vehicle networking application promote the emergence and development of UAV assisted vehicle networking system. In UAV assisted vehicle networking system, how to save energy and maximize system performance is significant for nodes with limited energy. This paper mainly considers how to choose the optimal communication network link to maximize energy efficiency in the process of UAV assisted vehicle network communication. Firstly, a mixed integer programming model is established for link selection in communication networks. Then a network transmission link optimization algorithm in terms of energy efficiency maximization is proposed to obtain the optimal transmission link and the corresponding energy allocation. Finally, the effectiveness of the proposed algorithm is verified by numerical simulation.

A dual-band filtering antenna based on a double-layer structure working in the n77/n78/n79 frequency bands is proposed. The antenna consists of two rectangular radiation patches on the upper substrate, step impedance resonators and two L-shaped branches on the lower substrate. The two dielectric substrates(FR4) are connected by probes. The two rectangular radiation patches on the upper dielectric substrate excite two resonant modes, among which the high-band resonance is employed to form the n79 frequency band, and the low-frequency resonance is employed to form the n77/n78 frequency band. In order to obtain the double bandpass filtering effect, a Step Impedance Resonator(SIR) is introduced into the lower dielectric substrate to form an out-of-band radiation nulls between the two frequency bands. In addition, the L-shaped branches on the lower substrate can introduce additional resonance points to expand the bandwidth of the antenna. The structure is optimized by High Frequency Simulation Software(HFSS). Its simulation results and test results cover the two frequency bands of 3.37~3.53 GHz(n77/n78) and 4.55~4.64 GHz(n79). The proposed antenna can be used for sub-6 GHz 5G wireless communication applications.

The model of Logarithmic Periodic Antenna(LPA) is built by the HFSS software. The LPA applied to Ultra High Frequency(UHF) detection of Partial Discharge(PD) signal is designed. In order to obtain the optimal parameters of the LPA, the HFSS simulation software is employed to change the relevant parameters such as antenna material, feed point position and dielectric substrate thickness, so as to obtain the optimal standing-wave ratio. The LPA with the optimal parameters is made of Printed Circuit Board(PCB). By comparing the insulation defect initial discharge voltage and PD signal with that of the Peano fractal antenna, the results show that the LPA has a lower initial discharge voltage, and the sensitivity of detecting electrical signals is higher than that of the Peano fractal antenna. In one discharge cycle, the number of PD detected by the LPA is slightly higher than that by the Peano fractal antenna, which indicates that the performance of the LPA is slightly better than that of the Peano fractal antenna.

A novel end-fire antenna with Split-Ring Resonants(SRRs) is designed. The antenna consists of a reflector, a floor, a radiation monopole and SSRs. By using the reflector structure, the impedance matching of the antenna is realized at low frequency, and the bandwidth of the antenna is improved effectively. The six pairs of SSRs structure are used as the director of the antenna to achieve the high gain of the antenna. The results of simulation and measurement show that the impedance bandwidth of the antenna is 73.7%(2~4.21 GHz), the gain is 4.3~10.3 dB. The radiation pattern of the antenna is stable within the bandwidth of the antenna. Therefore, the designed antenna meets the requirements of S-band wireless communication field.

A rectifier circuit composed of matching branches, rectifier diodes and DC-pass filters is presented, which is characterized by high efficiency, large power capacity and broadband. Two HSMS-282P Schottky diode bridges are utilized to design a single-stage voltage doubling rectifier circuit, which increases the input power capacity without decreasing the efficiency. The π type matching branch is adopted to realize the impedance matching, making circuit bear the characteristics of broadband. The short circuits in parallel can be used as the input filter, achieving miniaturization and improvement of the rectification efficiency. The DC-pass filter is employed to suppress the fundamental frequency and higher harmonics to improve the rectification efficiency. The measured results show that the rectification efficiency is greater than 60% within the bandwidth of 2.05~2.6 GHz. Working in the 2.45 GHz frequency and 35 dBm power input, the rectifier circuit in 330 Ω load wins 70% of the rectifier efficiency. The rectifier circuit has the characteristics of high rectification efficiency, large power capacity and wide frequency band, which can provide design guidance for designing high power microwave rectifier circuit.

An implantable antenna is required with miniaturization and stable frequency performance when working inside human body. A novel implantable antenna is proposed, which has a step shaped symmetrical structure fed by Coplanar Waveguide(CPW). A cube shaped human body model filled with muscle phantom is utilized in simulation with the antenna in the center of body. The antenna still covers Industrial Scientific Medical (ISM) band. The simulation results show that the antenna still covers ISM band when it is planted in different human tissues. The proposed antenna is measured in the human muscle solution and the measured bandwidth is 2.02-2.5 GHz. The size of the proposed antenna is 4 mm×11.9 mm× 0.8 mm with FR-4 as substrate. Compared with the published implantable antenna, the proposed antenna has the advantages of small volume, wide bandwidth, and low production cost, etc. The proposed antenna can be applied in implantable medical equipments such as pacemaker, capsule endoscope, etc.

Polarization purity of antenna is an essential technical indicator in radar or communication system.However, the poor cross-polarization level caused by non-ideal orthogonality of dual-line polarized antenna makes the imperfect performance of system. In response of this problem, the quantitative relationships among the polarization angle of electromagnetic waves synthesized in space, the phase value and the phase error of orthogonal channel are given by theoretical deduction. Finally, the experimental results verifies the correctness of the analysis.

In order to enhance the contrast of short.wave infrared image and improve the recognition ratio of target, a method of grayscale stretching algorithm based on Field Programmable Gate Array(FPGA) is proposed in this paper. According to the similar grayscale distribution between two consecutive frames, the parameters needed for image stretching are obtained by calculating the grayscale distribution of the previous frame, so as to process current frame, and real.time processing is achieved. In the grayscale statistics module, the design of non.frequency.multiplied pipelined logic is applied using the Block RAM resources on the FPGA chip. The proposed method avoids clock domain crossing in the grayscale distribution calculation process, reduces the complexity of the state machine, and improves the maximum operating frequency of the system. A domestic 320×256 InGaAs detector and an experimental platform based on Xilinx Artix-7 series FPGA are utilized to carry out the experiment. The results show that this method can effectively improve the contrast of the short.wave infrared image, which has the advantages of less resource utilization, fast computing speed, low cost, high portability, etc. and meets the design requirements of the real.time grayscale stretching of the short.wave infrared camera.

Aiming at the research and application needs in the field of meteorological observation, a thunder database for meteorological observations is designed and constructed, including stunned thunder, sputum and interference sounds, with 28, 33 and 61 samples, respectively, a total of 122 samples. Firstly, samples are collected, naming rules are formulated and labeled, and then the samples of the database are evaluated by using Support Vector Machine(SVM) and Group Sparse Least Squares Regression(GSLSR) model as a benchmark. The experimental results show that the establishment of the thunder database provides an important application basis and premise for the research of the meteorological field.

In order to improve the robustness of the Hashing algorithm for the content modification such as rotation, a robust image Hashing algorithm based on radial Tchebichef moment and Color Vector Angle(CVA) is designed in this paper. The 2D Discrete Wavelet Transform(DWT) is introduced to decompose the color vector angle of image for obtaining four sub-bands, and the low frequency coefficients are taken as structural features. The Tchebichef moments of pre-processing image are calculated based on radial Tchebichef moments to extract global features. And an intermediate Hash sequence is got by combining the two features. The encryption function is designed to encrypt the intermediate Hash for obtaining the target Hash sequence. Finally, the l2 norm distance between the initial target and the Hash sequence of the recognized image is calculated, and the authenticity discrimination of the image content is finished by comparing it with the preset threshold. The test data shows that this proposed Hashing algorithm is more robust than the existing Hashing algorithm, which can accurately identify the modifications of rotation, color and scaling.

An essential feature of energy internet is the two-way interaction between energy supply and consumption through advanced communication network. Therefore, the optimal configuration of highly reliable communication network based on optical fiber communication to meet Quality of Service(QoS) requirements of multiple services has become a key problem to be solved urgently. Starting with the reliability of power fiber transmission network and considering the multi-QoS transmission demand of power communication service, a circuit configuration optimization method based on compound measurement is designed. The new method is different from the traditional shortest path configuration algorithm. In one configuration process, m feasible configuration schemes are planned at the same time. In addition, the reliability of the entire optical path and different measurements of the path set, such as bandwidth, delay, packet loss rate, attenuation and cost, are analyzed. Finally, the optical path configuration scheme that meets the requirements of reliability and transmission QoS is finally obtained, and the priority selection sequence is given. The optimized configuration of multi-circuit will effectively improve the reliability of power communication and also provide a guarantee of circuit configuration for future multi-channel flow allocation. In the simulation of 35~500 kV power communication station network in an urban area, the new configuration method can obtain four transmission circuits that meet the demand of multi .QoS at the same time to realize the protection of main and standby circuits, which is of great theoretical significance to planning and operation optimization of the power optical transmission network and to the improvement of the resource allocation ability and reliability of the power communication network.

In order to improve the power system's ability to accept renewable energy output, reduce the equivalent load volatility of the regional power grid, maintain system security and enhance the response enthusiasm of the owners of Electric Vehicle(EV), taking the minimum load fluctuation in the grid power system, and the optimal economic benefits of the EV owners as the optimization goals, a collaborative scheduling model of large-scale EVs and renewable energy is established to reasonably arrange the charging and discharging behaviors of EVs. The maximum fuzzy satisfaction method is adopted to turn the multi-objective problem into a single objective problem. At the same time, an Improved Firework Algorithm(IFWA) is proposed. The algorithm performance is improved by optimizing the initial population distribution and a double elite-tournament selection strategy. Finally, by comparing the results of the calculation examples, it is verified that the coordinated scheduling of large-scale EVs and renewable energy can effectively suppress the fluctuation of equivalent load and create benefits for EV users. The improved algorithm reduces the computational overhead with a higher accuracy.