Abstract:Orthogonal Frequency Division Multiplexing(OFDM), Single Carrier with Frequency Domain Equalization(SC/FDE) and Multiple-Input Multiple-Output(MIMO) are the key techniques of next generation wireless communication. In this paper, the principles, research history and key issues of the above techniques are summarized, and OFDM research hotspots are analyzed in detail. Their applications in telemetry are discussed. Finally, it is concluded that OFDM should be widely used for aeronautical telemetry, and MIMO shows an enormous application potential for many telemetry systems, and Single Carrier Frequency Domain Equalization(SC-FDE) will be a new robust scheme for aeronautical and missile telemetry because it is very suitable to the environments of power-limited and severe multipath interference.
Abstract:This paper investigates several joint power allocation and relay selection strategies for wireless cooperative networks with Amplify-and-Forward(AF) protocols. These strategies aim at minimizing the total power consumption subject to some given Quality of Service(QoS)，which can be formulated to convex optimization problems. Using standard convex optimization techniques，closed-form solutions to these problems are obtained. Simulation results show that the proposed strategies can achieve lower power consumption than the traditional random relay selection and equal power allocation strategy.
Abstract:In order to realize reliable end-to-end communication in aeronautical mobile communica- tion between mobile terminal in aircraft and ground user host, this paper proposes some strategies such as higher initial sending rate, fast recovery for congestion, fast recovery for burst error. Comparing this algorithm with TCP Veno by using OPNET, the simulation results show that the proposed algorithm can solve the problem of high latency and burst error loss, and significantly increases the TCP throughput.
Abstract:Channel code is a key technique in satellite communications to improve reliability of lines of communication. The class of Low Density Parity Check(LDPC) codes is recommended by Consultative Committee for Space Data Systems(CCSDS) for application in deep space communication. To meet different requirements of varied space communication channels，a universal encoder that implements all codes in CCSDS is designed. It can save hardware resources and improve intersatellite availability for transplanting. Using VHDL language，the encoder is implemented on FPGA with less resources. The simulation results have verified the correction of the encoder.
Abstract:Effective choice of the solution is essential to achieve a real-time, bi-directional(full- duplex) communication of the smart grid. The Power Line Carrier(PLC) technology provides a low-cost solution, which suits China's own national conditions. In this paper, the advantages of OFDM PLC modulation technology are introduced. A PLC module of system model is established through the analysis of the input impedance under the low-voltage power line channel. The high-speed PLC module based on low-voltage Power Line is also designed according to the studies of power line channel. The results show that the design of the PLC module has featured high receiving sensitivity and anti-noise ability.
Abstract:In order to improve the performance of the Ultra-Wideband(UWB) under the situation of low signal and noise ratio，by using the UWB indoor channel model proposed by IEEE 802.15.3a study group，the performance improvement of the binary pulse position modulation Time Hopping Ultra-Wideband (2PPM-TH UWB) systems is analyzed in the case of employing multiple receive antennas. Under ideal power control, the diversity performance of 2PPM-TH-UWB systems is evaluated for different numbers of antenna elements and selected multipaths. The simulation results indicate that the system property becomes better as the number of antenna elements and Rake fingers increases, and the effects of the spatial diversity upon improving system performance are better than that of the temporal diversity.
Abstract:A Free Space Optical(FSO) cooperative communications technology based on photon counting is proposed. The network-coding relay cooperative mechanism and photon counting technology are used to achieve the enhancement of anti-fading ability under the precondition of good system performance. And Interleaver Division Multiple Access(IDMA) is adopted as multiple access method to reduce the complexity of system. The simulation results show that this system can provide good transmission performance and the relay cooperative mechanism can bring considerable spatial diversity gain in the fading channel.
Abstract:New features and development status of Digital Video Broadcasting(DVB)-S2 are analyzed compared to DVB-S. This paper proposes a novel search program of the DVB-S2 signal reception parameters based on TDQR-C005F, focusing on the search technologies of carrier center frequency and bandwidth parameters about the broadband signals，and three-step search technology and implementation of the algorithm concerning parameters of the signal channel including symbol rate，coding rate and pilot frequency. The algorithms and systems can meet the detection and identification requirements of the DVB-S2 burst signal compared to traditional algorithms. Experiments show that，the system can lock those conventional DVB-S/S2 signals accurately except for DVB signals whose bandwidth is below 2 MHz，reaching the search rate of 97.5%.
Abstract:To meet the software design requirements for Synthetic Aperture Radar(SAR) measurement and control system, the paper presents a method for designing software architecture based on hierarchically control after comparing several traditional design methods. Via this new approach, the measurement and control system software composition is divided into three levels(basic level, executive level and decisive level), and with the three libraries(information library, fault library and control library) management strategy for executive level, the classified management for task is achieved. At the same time, by establishing function matrix for every level, the mathematical model of software architecture is obtained, which provides a reference for coding.
Abstract:Jamming effect evaluation is an important method on judging and comparing with jamming methods. Based on analysis of sinusoidal frequency modulation and sawtooth frequency modulation jamming to SAR, it is obtained that the two methods can both produce mantle style and spot noise style jamming, which makes the jamming effect evaluation on the two jamming methods more difficult. Therefore two pertinent methods are adopted to make the evaluation more exact. The quantitative analysis of jamming effect evaluation is executed through the simulation.
Abstract:The carrier aggregation technology used in LTE-Advanced system is introduced in this paper. The challenges it brings to the security of Long Term Evolution-Advanced(LTE-Advanced) system are discussed. Based on the recent standard of carrier aggregation technology by 3GPP, the security requirements are presented and the corresponding solutions are provided according to the security scheme of LTE system.
Abstract:With the use of the even-odd mode analysis theory，a third-order 3 dB directional coupler is analyzed and designed by HFSS. On this basis，a ceramics chip is used as coupling medium，and a high-power third-order 3 dB directional coupler is analyzed and designed with the maximum input power above 17 kW. The adding of the ceramic chip can improve the coupler’s capability of voltage resistance and cut the size of the directional coupler, therefore high-power small-size coupling is achieved. This coupler can be applied to the high-power broadcasting transmitter system.
Abstract:In the design of the Ultra-wideband(UWB) reflector antenna，the most important problem is the matching between the radiation pattern of feeding antenna and the reflector. A rule in designing the reflector antenna in the frequency domain is that the radiation of the feeding antenna on the edge of the reflector is about -11 dB. The radiation patterns of Transmission Electron Microscopy(TEM) horn are simulated in different parameters，then some proper UWB reflector antennas are added and simulated to obtain higher amplitude of the far-field radiation by Computer Simulation Technology(CST) in 0 GHz–1 GHz. In the end，the simulation results are analyzed in the time domain. It is concluded that the radiation pattern of the TEM horn cannot match up with the reflector as the phase center of the TEM horn is uncertain, and when the TEM horn moves along the central axis，the field of the reflector surface changes，which leads to the change of the far-field radiation. At the same time，the effect of the shade of TEM horn should not be neglected.
Abstract:In order to improve the performance of Radio Frequency Identification(RFID) microwave rectifiers with microwave Schottky diodes, a compact microwave rectifier at 915 MHz was designed based on microstrip transmission lines in this study. The measured results show that the rectification efficiency is above 60% over the range of input microwave power from 13 dBm to 22 dBm. In the future, the performance of the rectifier can be further improved with better circuit designs, and it can be applied to microwave wireless power transmission systems and RFID rectennas.
Abstract:The digital Phase Locked Loop(PLL) frequency synthesizer technology is researched and analysed based on phase noise performance. An X-band PLL frequency synthesizer based on dual loop technology is introduced in contrast to conventional single locked loop technique. This design features small frequency step and low spurious characteristics with phase noise below -100 dBc/Hz@1 kHz.
Abstract:This paper proposes a new method to implement change of polarity of cross-coupling in microstrip cross-coupling filter and cavity cross-coupling filter by the use of transmission line. To realize the cross-coupling between the source and a nonadjacent resonator by using a transmission line with an electrical length of 180°in microstrip cross-coupling filter, can make the polarity of cross-coupling change from capacitive to inductive. Using a transmission line with an electrical length about 180°in cavity cross-coupling filter, transmission zero can be shifted from upper stopband to lower stopband. A discussion of the effects of different electrical length transmission line on cross-coupling is presented. The positions of transmission zeros can be controlled by adjusting the lengths of transmission lines to improve the rejection level. With this proposed method, transmission zeros can be positioned arbitrarily using the same coupling structure, which makes the filter design more flexible.
Abstract:As the development of multicarrier communication technology, multi-channel signal generator has become more and more important. Based on the Direct Data Synthesis(DDS) technology, this design uses FPGA to control the AD9910 to implement a kind of multi-channel signal generator. This multi-channel signal generator features high frequency precision, low stray, fast frequency switching, and programmable adjustment of the multi-phase value of the output signal. Measured results show that this method is feasible and effective, and it would be widely applied in the future.
Abstract:The nonsymmetrical scattering matrices of bistatic Synthetic Aperture Radar(SAR) are studied on the basis of the analysis of the monostatic SAR deorientation parameters, and the bistatic deorientation parameters are obtained by using matrix algebra. Deorientation transformation matrix is deduced and the transformation of the target scattering vector is introduced to reduce the influence of randomly fluctuating orientation and make the targets’ generic characteristics prominent. The targets’ generic characteristics of the simulated bistatic SAR images are analyzed through the transformation in order to provide a rudimentary method for bistatic SAR images.
Abstract:There are some problems existing in common radar signal sorting methods, which are easy to generate Pulse Repetition Interval(PRI) harmonics and split the pulse stream belonging to the same radar into several pieces. In view of these problems，this paper presents an improved algorithm for radar signal sorting basing on an intercept of Time of Arrival(TOA) fitting straight line analysis algorithm. The algorithm can solve these two problems to a large extent. In the improved algorithm of radar signal sorting，the two situations mentioned above are judged by analyzing the intercepts of TOA fitting straight lines，and then corresponding pulse sequences are merged to obtain the correct sorting results. The intercept analysis algorithm enhances the robustness of the sorting algorithm to reduce the algorithm dependence on search tolerance，and it shows good engineering application value. The simulations have proved that，the sorting probability of improved algorithm is higher than that of Sequential Difference histogram(SDIF) by 20%.
Abstract:Most of methods for image fusion are based on only one characteristic of image, which is liable to cause some information loss about other characteristics. In order to solve this problem, a new method for image fusion based on Haar wavelet and multi-characteristics is proposed. After Haar wavelet transformation, the low-frequency part is fused by gradient and energy since it contains most energy of the image. And the high-frequency part is fused by variance and transforming coefficient because it reflects the details of image. Finally, the inverse transform is performed to obtain fused image. After multi-group images fusion by this method, the performance of image fusion is evaluated by four criteria including average value, variance , entropy and average gradient. It is indicated that this method can keep the image information very well, and the fusion effect is good.
Abstract:A highly efficient Graphics Processing Unit(GPU) based method for decomposing SAR azimuth signal is presented. SAR azimuth signal is decomposed by the four-parameter Chirplet decomposition method. This method needs excessive computation mainly to construct Chirp atomic dictionary and decompose SAR azimuth signal in the over-complete dictionary. Compared with CPU, GPU is well suited for data parallel computations with high arithmetic intensity. A new method is introduced that takes full advantage of GPU’s computation capability by transferring the key part of the algorithm to GPU.The experimental results shows that this method is more than ten times as fast as traditional CPU based algorithms.
Abstract:In order to repair the broken core image，this paper proposes an inpainting algorithm based on neighborhood pixels and wavelet de-noising. Firstly，the priorities of the pixels which need repairing are calculated in order to determine the filling and inpainting order；then，the pixels are repaired with the neighboring information and the improved weighting function；finally，the de-noising of the restored core image is performed by wavelet de-noising. The algorithm combines image inpainting and wavelet de-noising，and obtains excellent results in repairing experiments.
Abstract:To enhance the operation speed and utilize the resource，according to the idea of hardware parallel method，one traditional implementation of genetic algorithms is improved by separating controlling part into other components and using Field Programmable Gate Array(FPGA) to realize control in pipelining mode. The result of synthesis shows its frequency can reach 137.08 MHz for evolution of a generation needing 64 cycles(namely 0.467 μs). With optimized hardware resources and high efficiency, the realized structure demonstrates the possibility of large-scale and high-speed hardware realization of genetic algorithms.
Abstract:Solid-state pulsed power is a hotspot in the research of pulsed power. A multi-channel trigger control system，which is applied to the solid-state modulator，has been designed and tested. Under the control of Field Programmable Gate Array(FPGA) and Micro Control Unit(MCU)，the trigger signal features a high pulse-repetition rate in burst mode，while the pulse width and frequency of every sub-pulse can be adjusted individually in real time. Between the trigger system and the power system, optoelectronic isolated circuit is adopted to reduce the interference of high power system on the low power system. The generator shows certain distinct advantages as convenient operation，steady run，simultaneous multi-channel output and so on. The generator can output 240 synchronic trigger signals at most，and the maximum of 4 pulses burst. The design of the signal generator and the measured data of performance are presented in this paper.
Abstract:A new Lateral Insulated Gate Bipolar Transistor(LIGBT) on Silicon On Insulator(SOI) substrate with Super Junction(SJ) technology and anode assistant gate structure is proposed and discussed. This device shows low on-state voltage drop due to the SJ structure and high switching speed with the adoption of anode assistant gate structure. Simulations about how the key parameters (doping of Pdrift region, length of anode gate) influence the turn-off time are performed and the results show that switching performance of the proposed device can be improved by 30% compared with traditional LIGBT.
Abstract:According to the lack of efficient analysis tool for Quick Access Recorder(QAR) data, an improved data mining method is proposed in this paper. First, a modified algorithm of k-means based on probability theory is given. Then the cluster number of QAR data set is determined, so that better cluster results can be obtained. In order to identify the atypical data and the class of typical data, a weighted minimum distance classification as well as probability analysis is used. At last, experiments of cluster and classification are given to indicate the feasibility and effectiveness of the new method.
Abstract:According to the characteristics of robot duty，this study designed a monocular vision system. With Complex Programmable Logic Device(CPLD) to form the control timing sequence，a Complementary Metal Oxide Semiconductor(CMOS) image sensor was adopted to build up a hardware platform with a resolution of 0.3 M pixel. Based on the simplified Hue Saturation Intensity(HSI) color model, the object status could be judged with a sampling method. The high-performance Digital Signal Processing(DSP) processor used could provide image processing and motion control functions simultaneously. The algorithm was verified with Matlab and then ported to DSP. Experimental result has shown that the system can implement the status judgment successfully.