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1.
希尔伯特变换是一种非常有用的数学方法,用来描述一个以实数值载波做调制信号的复数包络,使该调制信号的时域表示简单明了。希尔伯特滤波器则用来实现调制信号的希尔伯特变换。用Weaver法可以很好解决希尔伯特滤波器的实现难题。以单边带调制为例,介绍了Weaver法实现希尔伯特滤波器的基本方法。 相似文献
2.
Advances in GPR-based landmine automatic detection 总被引：1，自引：0，他引：1
As an application of mechatronics, this paper presents the advances in surface-adaptive ground penetrating radar (GPR)-based anti-personnel landmine detection project in Nagoya University. These advances can be summarized in three items: (1) GPR manipulation where a low-pressure-tire vehicle capable of moving inside a mine field, to facilitate machine-based sensing in place of manual sensing, is applied; (2) enhancement of underground landmine suspects’ images through geography adaptive scanning and measurements signal processing of a vector frequency modulated continuous wave (FMCW) GPR; (3) GPR fusion with metal detector (MD) for automatic decision making through experimental-based fuzzy learnt fusion rules. The state-of-art of these advances as well as directions for future research work is to be presented. 相似文献
3.
在通信收发系统中,功率放大器位于发射机末端,其作用是将高频已调波信号进行功率放大,以满足发射机发送功率的要求,然后经过天线将高频功率信号辐射到空间,保证在一定区域内的接收机可以接收到满意的信号电平,并且不干扰相邻信道的通信。本文叙述了功率放大器的特性及发展历程,着重分析了射频功放的非线性及功放线性化的几种常用技术。 相似文献
4.
本文将单片机技术用于实现移频自动闭塞系统的移频信号解调，结果表明该系统不仅能正确地从接收到的信号中提取出低频脉冲调制信号，还能有效地抑制由轨道电路引入的各种干扰，在各种复杂信道条件下都能获得较高的信噪比。 相似文献
5.
一种基于时频分析的超宽带脉冲构造方法 总被引：1，自引：0，他引：1
频谱共存和兼容是超宽带无线通信系统的一个关键问题。为避免该系统与现有无线通信系统之间的相互干扰，同时尽可能地利用频谱资源，有必要对脉冲波形进行合理设计。本文在脉冲信号的时频分析基础上，设计了一种具有升余弦滚降频谱的超宽带脉冲波形，该脉冲波形时域持续时间短，频域上满足FCC的规定；并构造出具有正交特性的时域脉冲波形，使之适用于高阶调制下的超宽带系统。 相似文献
6.
本文首先介绍了星载SAR回波信号仿真相关技术,包括星地空间几何模型、回波信号数学模型和距离频域脉冲相干法。在此基础上给出了一种星载SAR回波信号仿真方案,并详细给出了其仿真算法流程。然后通过对仿真算法流程的并行性分析,以并行编程标准OpenMP为基础对仿真算法进行了并行化。仿真实验结果证明了并行仿真算法的正确性和高效性。 相似文献
7.
冲击信号是一种瞬态信号,对其进行采集和分析需要提供完善的信号触发控制、采样频率自动设置及采样点数自动控制等功能。本文在分析了实现冲击信号采集特点及原理的基础上,研究并设计了基于CPLD(复杂可编程器件)的硬件功能模块。文中在生成系统时钟上采用了基于有限状态机的方法,完全在CPLD芯片中实现分频,取代了常见的使用8254可编程芯片的做法。此外,在模块中设计了采样频率设置、采样点数自动计点等功能,同时还可以用硬件实现多通道信号自动触发的功能,可以实现超前触发、滞后触发、电平触发、沿触发、触发电平自动设置等功能。所有的触发逻辑都使用verilog硬件描述语言在CPLD芯片中实现。通过和A/D电路配合工作,硬件模块可以实现采样的自动化。 相似文献
8.
G. A. Ferrier A. N. Hladio D. J. Thomson G. E. Bridges M. Hedayatipoor S. Olson M. R. Freeman 《Biomicrofluidics》2008,2(4)
The mechanical behavior of cells offers insight into many aspects of their properties. We propose an approach to the mechanical analysis of cells that uses a combination of electromanipulation for stimulus and capacitance for sensing. To demonstrate this approach, polystyrene spheres and yeast cells flowing in a 25 μm×100 μm microfluidic channel were detected by a perpendicular pair of gold thin film electrodes in the channel, spaced 25 μm apart. The presence of cells was detected by capacitance changes between the gold electrodes. The capacitance sensor was a resonant coaxial radio frequency cavity (2.3 GHz) coupled to the electrodes. The presence of yeast cells (Saccharomyces cerevisiae) and polystyrene spheres resulted in capacitance changes of approximately 10 and 100 attoFarad (aF), respectively, with an achieved capacitance resolution of less than 2 aF in a 30 Hz bandwidth. The resolution is better than previously reported in the literature, and the capacitance changes are in agreement with values estimated by finite element simulations. Yeast cells were trapped using dielectrophoretic forces by applying a 3 V signal at 1 MHz between the electrodes. After trapping, the cells were displaced using amplitude and frequency modulated voltages to produce modulated dielectrophoretic forces. Repetitive displacement and relaxation of these cells was observed using both capacitance and video microscopy. 相似文献
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11.
T.W. Parks 《Journal of The Franklin Institute》1974,297(4):229-242
An efficient procedure for signal representation, based on known signal properties, is presented. The representation minimizes the maximum of the ratio of the error and the signal norm, the per cent error. Signal classes are specified by normalized quadratic functionals. These results are contrasted with the theory of n-widths of signal classes, and several applications are developed. 相似文献
12.
刘伟 《中国科学院研究生院学报》1996,(2)
声纳阵信号模拟在声纳设计中起非常重要的作用．提出一种阵信号模拟算法．通过寻址一个标准信号表来产生不同频率及延时信号，利用模１加法反馈法产生噪声序列．该算法运行于一个双ＴＭＳ３２０Ｃ２５的并行流水线结构硬件平台上．实验证明设计是正确有效的． 相似文献
13.
Andrew Sobczyk 《Journal of The Franklin Institute》1948,246(1):21-43
In this first part a method of analysis of linear carrier-frequency systems is indicated, and applied in particular to electrical servomechanisms using a two-phase alternating-current control motor. The performance of such a servo, as regards stability and fidelity of the output as a copy of the input, depends on the action of a controller-demodulator unit including the motor. A calculation of the steady-state effect of a linear transfer characteristic on the suppressed-carrier modulated error signal makes possible application of the Nyquist stability criterion.The method does not require symmetry of the characteristics about the carrier frequency; if such symmetry is present the system is similar to an ordinary or d-c. servo. Thus a band-rejection network tuned to the carrier frequency has an approximate proportional plus derivative action on the envelope of the error signal, resulting in an “anti-hunt” or stabilizing effect similar to that due to a translated band-rejection characteristic (center at zero-frequency) in a corresponding d-c. servo.A procedure is given for construction of transformed Nyquist diagrams, or gain-phase margin diagrams. The effect of the correctly tuned band-rejection network, as well as the effects of bandwidth, of the network being tuned off the carrier frequency, of increasing gain or velocity constant kν, and of the use of phase-shifting networks, are clearly shown by a series of such diagrams. 相似文献
14.
信号序列的DFT本身就是信号频谱的采样集,所以DFT可直接用于分析信号的频谱。快速傅立叶变换是一种有效、实用的信号DFT算法。文章通过对DIT-FFT算法的详细分析,提出了一种计算机软件仿真信号频谱分析方案,并给出了关键算法的C语言程序。 相似文献
15.
Load voltage waveforms corresponding to symmetrical phase-angle triggering and integral-cycle triggering in single-phase thyristor circuits, and also the waveform due to half-wave rectification, are all discrete forms of amplitude modulation. In each case the modulated output voltage is obtained from a sinusoidal (supply) carrier signal by use of a rectangular modulating function, dependent on thyristor switching.The use of amplitude modulation (AM) techniques for frequency conversion in high power applications is subject to certain severe restrictions of performance. These restrictions can be largely overcome by the use of phase modulation (PM) methods which involve two channels of AM in each electrical supply line.Appropriate waveforms may be realised by the use of controlled switching of thyristors. These are arranged in combinations of inverse-parallel connected pairs forming subtractor modulators. Certain thyristor commutation problems arise in PM systems at high power levels. These problems can be overcome by producing so-called AM/PM waveforms that combine the separate advantages of AM and PM systems. 相似文献
16.
Wojciech Ros?oniec 《Journal of The Franklin Institute》2010,347(8):1452-1467
Radar systems usually had used digital signal processors for signal processing in the past. Such an approach has changed after introduction of a new type of general purpose PowerPC processor with very fast vector units called AltiVec. This new type of processor could realize various tasks performed earlier by several specialized processors. For instance it could be used for digital signal processing, tracking, fusion of data or communication with other functional blocks of radar. Its versatility and speed proved to be a superior solution in modern radar systems. It could also be programmed using C language instead of an assembler, what facilitated software development. Unfortunately the memory subsystem of computers built using this type of processor appeared to be too slow, and consequently slowed down the calculations. Therefore, the signal-processing software written for PowerPC processors with AltiVec vector units had to be accordingly optimized. The paper presents various optimization techniques and their effect on mean processing time of signal-processing software.The computer system built of industrial computers connected by the internal Ethernet is also presented in the paper. Individual computers of this system contain the multi-core PowerPC processors equipped with AltiVec vector units. The experimental model of the system is used for real-time digital processing of the multi-stream radar signals. The presented results of theoretical and experimental investigations show that the system is an effective, universal and cheaper computational platform than the corresponding, traditional multiprocessor platforms using the signal processors. Selected example recipes of writing the optimum and reliable application software are also given. 相似文献
17.
Ram M. Narayanan 《Journal of The Franklin Institute》2008,345(6):659-678
This paper examines the results of our research on the use of ultrawideband noise waveforms for imaging objects behind walls. The advantages of using thermally generated noise as a probing signal are introduced. The technique of heterodyne correlation used to inject coherence in the random noise probing signal and to collapse the wideband reflected signal into a single frequency are presented. Central to successful imaging through building walls is the characterization of the wideband propagation properties of wall materials and these are discussed. The basic concepts of synthetic aperture radar image formation using noise waveforms and the unique problems associated with the random nature of the transmit waveform are analyzed. We also address issues related to locating, detection, and tracking humans behind walls, using new tools for human activity characterization, namely the Hilbert-Huang Transform approach. The results indicate that noise radar technology combined with modern signal processing approaches is indeed a viable technique for covert high-resolution imaging of obscured stationary and moving targets. 相似文献
18.
基于传输函数的信号流图模拟,一种新的具有最少元件 Ｏ Ｔ Ａ电容滤波器结构被提出⒚任何种类任何阶电压传输函数均可由该结构实现,设计公式简单⒚文中设计了各种二阶滤波器,分析了这种实现的电压传输函数的灵敏度,给出了三阶椭圆低通滤波器设计实例及计算机仿真结果⒚ 相似文献
19.
Y.C. Jenq 《Journal of The Franklin Institute》1979,307(5):291-303
Data transmission via optical fiber is a new discipline of communication theory. The principal difference from conventional baseband data transmission, which is characterized by a signal independent additive Gaussian noise, is the existence of a signal dependent shot noise.This paper presents a technique for estimating the error probability performance of digital systems with inter-symbol interference and signal dependent additive noise. For binary antipodal (±1) systems, the approximate upper bound to the error probability is twice the lower bound. Hence either can be taken as a good approximation to the actual error probability. The technique is then applied to a model of some promising optical data communication systems and a good approximation to the error probability is obtained. Some observations about the effect of various system parameters on the error probability and some numerical examples are presented. 相似文献
20.
提出了一种采用声信号时域自相关检测挠性剑杆织机同步运作性状的方法,并应用这种方法,对织机运行产生的声信号进行预处理,测定声信号的时域自相关函数,给出织机同步运作性状的分析结果。实验结果表明,这种方法是有效的,可以作为无损检测该型织机同步运作性状的一种技术手段。 相似文献