伪码均匀性对信号功率测量的影响

在扩频体制导航信号模拟源功率测量中,出现了长周期伪随机码调制信号的功率测量值波动范围明显大于短周期伪随机码调制信号功率测量值的现象。针对这一现象,该文从理论上分析了测量值产生波动的原因,并通过实验进行了验证,得出了伪随机码在测量时段内的码均匀性影响信号功率测量准确度的结论,提出了规避或降低由码均匀性引起测量误差的解决措施。     

基于FPGA的激光脉冲编码研究

对目标指示信号进行编码能够有效的降低敌方的干扰,详细介绍了激光指示信号3种编码样式,即脉冲间隔编码（PCM）、有限位随机周期脉冲序列编码和伪随机码。对3种编码的特点进行了全面的分析,并从原理上说明了激光脉冲编码的生成机理。通过Modelsim软件对2种脉冲编码进行了仿真研究,并对有限位随机周期脉冲序列编码和伪随机码的特点进行了比较,伪随机码具有更好的保密性和抗干扰能力。     

直扩技术分析及其应用

扩频通信技术由于具有抗干扰能力强，信号隐蔽性好，容易实现多址传输等优点而在卫星通信、数据传输、移动通信、无线数据通信等领域的应用日益广泛。其中直扩通信技术是目前使用的最典型扩频工作方式，弄清楚扩频和解扩处理过程的机制，是理解直接扩频通信技术本质的关键所在。首先介绍了直扩通信系统的基本工作原理，其次结合构建的系统模型，对其扩频和解扩的机制进行了详尽分析，提出了采用直扩技术通信的优势。最后给出了直扩技术在国内外的应用现状。     

伪随机码用于靶场武器系统的精密测时

伪随机码具有类似于白噪声的自相关函数及频谱特性,具有扩展频谱的功能,具有较强的抗干扰能力。伪随机码广泛应用于通信及测控领域。介绍了伪随机码的主要特点,简要描述了伪随机码测时的工作原理,对系统的测时精度进行了详细分析、计算并得到了期望的结果。分析及试验表明,系统测时精度满足任务要求。最后得到结论,利用伪随机码技术进行靶场武器系统的精密时间测量是可行的。     

新型光数字信号取样测量与两步分析模型

提出将电吸收调制器(EAM)应用于数字光通信信号监测的频差法测量中，大大简化了传统频差法测量的复杂性。在实验中，对10GHz正弦光信号序列取样，得到100MHz的低频信号波形。分析了EAM的取样窗口宽度与测量系统带宽之间的关系，并提出利用两步模型分析取样宽度对伪随机码信号取样测量的系统带宽的影响，提出采用高斯低通滤波器能够很好的估算EAM取样窗口宽度与取样系统带宽的关系。分析表明，EAM同步取样系统在测量实际数字光通信系统中具有很大的应用潜力。     

基于DSP的声磁EAS系统设计

针对射频EAS系统的低检测灵敏度、高误报率等缺陷,设计了一种基于DSP的声磁EAS系统。阐述了系统检测装置的硬件结构及工作时序,分析了声磁标签信号的特征,提出了一种声磁标签信号的检测方法。经过实验测试,系统的抗干扰性能、检测率、误报率等特性都比射频系统有显著的改善。     

射频EAS系统的抗干扰研究

目前,射频EAS系统的市场应用仍十分广泛,伴随着日益严重的电磁干扰,其抗干扰性能面临着更大的挑战。此文针对一体式射频EAS系统如何提高其抗干扰性能进行研究。根据不同干扰噪声的特点,对稳态干扰和瞬时干扰在系统工作的各个环节上的影响进行分析,有针对性地给出了一系列包括硬件和软件等方面的方法,提出了一种以信噪比为基础提高系统自适应能力的算法,并结合实验仿真进行了验证,结果表明,本方法提升了系统的抗干扰能力和稳定性。     

基于光电扫描的三维坐标测量系统

wMPS测量系统是一种新型的基于光电扫描的坐标测量系统,当系统工作时,激光测站分布在测量空间四周,扫描信号覆盖整个工作空间,位置传感器通过扫描信号测量与多个测站之间的方位角计算三维坐标.与其他测量系统相比,具有能够同时跟踪测量多个目标、抗干扰能力强、自动化程度高、简单易用等特点,适用于现场条件下的大尺寸测量.针对数字化...     

基于FPGA平均值原理相位差计的设计

相位差的测量在研究网络特性中具有重要作用.设计一个测量快速、精确的相位差计已成为生产科研中重要课题.提出了基于平均值原理相位差计的设计方法,采用FPGA芯片实现了平均值相位差计,重点时相位差测量中的超前与滞后判断、输入信号处理、相位差计数器、锁存显示等几个数字环节进行VHDL语言编程,顶层用原理图方式构建了相位差测量系统.该系统电路结构简单,占用逻辑资源少,抗干扰能力强,可靠性高.     

基于P89LPC932单片机与CS5460A芯片的电能测量及显示

随着电网智能化、网络化的发展，传统机械式电能测量已无法满足要求。针对这种状况，提出了一种新型智能电能测量方案，即应用新一代8位单片机LPC932与电能专用芯片CS5460A进行电能测量及显示。由于此方案集成化程度高、抗干扰能力强、功耗低等优点能充分满足电能智能化管理要求。此方案集中讨论影响系统精度、稳定性的软硬件设计，而对一般说明性内容只做简单介绍。     

一种新的跳频脉冲信号的运动补偿方法

随机跳频脉冲信号的运动补偿是雷达信号处理中的难点，本文采用伪随机的方式，即在各脉组间采用同一随机编码序列，来产生随机跳频脉冲信号，从而大大简化了信号的复杂度，并在此基础上设计了一种简单可行的运动补偿方法——前后正负跳频脉组比较法。分析表明，采用伪随机的方式对原始信号的分辨性能没有太大的影响。所提出的方法具有运算量少，处理实时方便的优点。     

Coding digital information with the use of generators with chaotic dynamics

A new method for coding graphic information is proposed. The method is based on the change in the color of each image symbol according to a pseudorandom law. Artificially designed self-oscillatory systems are used for generating a pseudorandom sequence of numbers. Results of studying the employed pseudorandom-signal generators and of encoding/decoding a color image are presented. The effect of damage in an encoded image on the restoration process is considered.     

Concatenated combined modulation and coding of frequency hoppingmultiaccess systems

A spread-spectrum system that does not have a separate state for initial code acquisition is presented. A uniform random variate selects one of several Gold codes for transmission, thus removing the notion of pseudorandom codes from spread-spectrum systems, making the effective code length infinite, and leading to acquisitionless systems. Because coding is critical to the proposed multiaccess frequency-hopping (FH) system, more powerful codes are needed. The performance of the proposed multiaccess system using the combined modulation and coding technique (trellis) concatenated with Reed-Solomon codes in partial-band jamming is investigated. The FH multiaccess performance of noncoherent soft detection of MFSK in association with trellis coding is introduced and the performance compared to that using RS outer/RS inner concatenated codes     

对称型全帧行扰乱电视图像加/解密器

介绍一种电视图像加／解密装置。加密器逐帧将标准电视图像（PAL制或NTSC制）扫描行的有效图像部分按预定的随机次序相互交换，获得无法辨认画面内容的加密电视信号，但信号本身仍符合原制式标准；解密器与加密器同样方法工作，将加密电视信号恢复或原信号；加／解密器的随机次序是对称的，加密器本身可当自己的解密器，即一对加／解密器是一样的。本装置可应用到有特殊需求的闭路电视监视系统中。     

Satellite altimetry using ocean backscatter

A model for the signal received when satellite altimetry pulses are scattered back by the ocean's surface is postulated and analyzed. The second-order statistics of the complex nonstationary random process appearing at the detector input are graphically and analytically displayed as a function of the sea state. The standard deviation of various altitude estimates derived by subsequent operations on the detector output are computed, too. The analysis applies both to ordinary short-pulse altimeters and to systems that employ pulse compression.     

A Software-Optimized Encryption Algorithm

We describe the software-efficient encryption algorithm SEAL 3.0. Computational cost on a modern 32-bit processor is about 4 clock cycles per byte of text. The cipher is a pseudorandom function family: under control of a key (first preprocessed into an internal table) it stretches a 32-bit position index into a long, pseudorandom string. This string can be used as the keystream of a Vernam cipher. Received 3 May 1996 and revised 17 September 1997     

Efficient hardware implementation and analysis of true random‐number generator based on beta source

This paper presents an efficient hardware random‐number generator based on a beta source. The proposed generator counts the values of “0” and “1” and provides a method to distinguish between pseudo‐random and true random numbers by comparing them using simple cumulative operations. The random‐number generator produces labeled data indicating whether the count value is a pseudo‐ or true random number according to its bit value based on the generated labeling data. The proposed method is verified using a system based on Verilog RTL coding and LabVIEW for hardware implementation. The generated random numbers were tested according to the NIST SP 800‐22 and SP 800‐90B standards, and they satisfied the test items specified in the standard. Furthermore, the hardware is efficient and can be used for security, artificial intelligence, and Internet of Things applications in real time.     

Radio wave loss deviation and shadow loss at 900 MHz

Radio wave propagation between base and mobile stations is normally described as being Rayleigh distributed due to multipath radio wave combining. When the number of radio wave paths are limited the variation in received signal amplitude frequently follows a more general case given by a Weibull distribution. A significant portion of the Weibull distribution is defined as the transmission loss deviation. Other definitions have been included with the object of standardizing methods of measuring and reporting propagation data. Data will be presented showing loss deviation between 3 and 30 dB. Shadow loss over hills and around buildings are usually assumed to be knife-edge or rounded knife-edge. Shadow loss based on these assumptions is generally found to be less than the true measured value. Data will be presented comparing calculated shadow loss with measured value.     

A New Hybrid Random PWM Scheme

This paper proposes a new hybrid random pulsewidth modulation (PWM) scheme based on a TMS320LF2407 DSP, in order to disperse the acoustic switching noise spectra of an induction motor drive. The proposed random PWM pulses are produced through the logical comparison of a pseudorandom binary sequence (PRBS) bits with the PWM pulses corresponding to two random triangular carriers. For this reason, the PWM pulses of the proposed scheme possess the hybrid characteristics of the random pulse position PWM and the random carrier frequency PWM. In order to verify the validity of the proposed method, the simulations and experiments were conducted with a 1.5-kW three-phase induction motor under the 2.5-A load condition. The DSP generates the random numbers, the PRBS bits with a lead-lag random bit (8 bit) and the three-phase reference signals. Also, a frequency modulator MAX038 makes the randomized frequency triangular carrier (3 $pm$ 1 kHz). From the results, the proposed scheme shows good randomization effects of the voltage, current, and acoustic noise of the motor as compared with conventional scheme (3 kHz).      

Pseudorandom Poisson-process generator

A method for generating an impulse train or a binary signal (random telegraph waveform) with pseudorandom Poisson statistics is described. It uses the properties of the binomial distribution to approach the Poisson distribution in the limit. A simple digital-hardware implementation, based on this method, is presented, and some test results are given.