QPSK数字化解调中载波同步技术研究

分析了判决辅助载波同步和非判决辅助载波同步的基本原理,研究了基于信号相位的载波频偏估计算法和基于信号自相关函数载波频偏估计算法,提出了基于恒包络零自相关(CAZAC)序列为前导的载波同步算法,并对基于CAZAC序列的载波恢复算法进行了分析和计算机仿真,结果表明该算法性能优良且实现简单。     

相位凝固技术中干涉信号调制解调误差分析

为了进一步减小基于相位凝固技术的激光反馈干涉系统测量运动物体微位移时的测量误差,采用MATLAB数值仿真及曲线拟合的方法,对移相间隔和外腔反射面振动幅度引起的系统误差进行了理论分析。在系统实验中依据相位凝固原理对物体运动产生的干涉信号进行采样,获取多组光功率曲线,在光功率曲线上实时判向并标记特征点。根据特征点重构被测物体的微位移曲线,对重构得到的微位移台阶曲线进行多项式拟合以提高测量精度。结果表明,在固定移相间隔为/5、激光器波长为1550nm的情况下,测量分辨率优于/20(77.5nm),实际测量的绝对误差最大值为47.98nm,峰峰值误差平均值小于1nm。相位凝固技术调制解调干涉信号为微位移的方向辨识和高精度测量提供了新的解决方案。     

A digital signal processing type frequency locked loop for frequency shift keying demodulation

In this paper, we propose a digital signal processing type frequency locked loop (DSP-FLL) using a frequency difference detector (FDD). Since the DSP-FLL is controlled by the frequency, the pole of the voltage controlled oscillator vanishes in the baseband equivalent circuit. Therefore, the transfer function becomes first order and a ringing does not occur. Furthermore, it can be understood from the detection property of the FDD that a cycle slip does not occur and the DSP-FLL can pull in the frequency step input up to half of the sampling frequency.     

Coherent demodulation of optical multilevel phase-shift-keying signals using homodyne detection and digital signal processing

We demonstrate coherent demodulation of optical multilevel (M-ary) phase-shift-keying (PSK) signals. Since the carrier phase is estimated accurately through digital signal processing after phase-diversity homodyne detection, the system performance is highly tolerant to the carrier phase noise. By off-line bit-error-rate measurements using distributed feedback semiconductor lasers with linewidths of 150 kHz as a transmitter and a local oscillator, it is shown that binary PSK (M=2), quadrature PSK (M=4), and eight-PSK (M=8) signals are successfully demodulated at the symbol rate of 10 Gsymbol/s.     

Optimal detection of a BPSK signal contaminated by interference andnoise

The problem of detecting a desired binary phase-shift keying (BPSK) modulated bit in the presence of a second BPSK modulated interfering signal and additive white Gaussian noise is considered. Given knowledge of the amplitudes and phases of the unmodulated signals received from the two transmitters, the minimum achievable bit error rate is obtained and compared with that for a conventional matched filter detector. It is shown that the performance difference can be quite large when the interfering signal is strong     

Optimal demodulation of PAM signals

Kalman filtering theory is applied to yield an optimal causal demodulator for pulse-amplitude-modulated (PAM) signals in the presence of white Gaussian noise. The discrete-time data (or sampled continuous-time data) are assumed to be either a stationary or non-stationary Gaussian stochastic process, in general nonwhite. Optimal demodulation with delay is also achieved by application of Kalman filtering theory. The resulting demodulators (fixed-lag smoothers) are readily constructed and their performance represents in many cases a significant improvement over that for the optimal demodulator without delay. The fixed-lag smoothing results are in contrast to those for amplitude-modulated signals (AM) where only approximate fixed-lag smoothing is possible, and this with considerable design effort. The performance of the optimal PAM demodulator is shown to be equivalent to that of an optimal discrete filter for the discrete data.     

Error probability for multilevel digital systems in presence ofintersymbol interference and additive noise

Generalization of a recently published technique for the evaluation of error probability in fiber-optic communication systems is described. The crux of the method is a minimax approximation of the cumulative distribution function of the additive noise. The additive noise is not constrained to be Gaussian. Examples and comparisons with previously published techniques are presented     

铁路数字电视与既有无线列调的信号干扰分析

铁路数字电视的发展是和谐社会的需要.基于无线列调对铁路运输安全的重要性,在研究铁路数字电视之初,必须考虑到铁路数字电视系统对既有的无线列调系统不能造成干扰.在对两个系统进行对比分析研究的基础上,排除了铁路数字电视信号对无线列调的信号存在干扰的可能,为铁路数字电视的发展提供了切实有效的基础.     

Optimal combined word-length allocation and architectural synthesis of digital signal processing circuits

In this brief, we address the combined application of word-length allocation and architectural synthesis of linear time-invariant digital signal processing systems. These two design tasks are traditionally performed sequentially, thus lessening the overall design complexity, but ignoring forward and backward dependencies that may lead to cost reductions. Mixed integer linear programming is used to formulate the combined problem and results are compared to the two-step traditional approach.     

数字信号处理对电子测量与仪器的影响

随着经济社会的发展,测量工作在社会生产中的应用越来越重要,电子测量仪器作为其中不可或缺的测量设备,如何提高其测量效果已成为当前重要的研究课题,本文就数字信号处理对电子测量与仪器的影响展开了探讨,希望为测量性能的提高提供一定借鉴.     

高效QAM信号解调设备的研制

根据高效QAM信号解调设备的功能指标、技术指标要求,采用ADC、FPGA、数字信号处理、单片机和数字解调等技术,实现对高效QAM信号的有效解调,满足了高质量的军事侦察和控守能力,解决了解调入锁门限高、误码率高、解调速率不能连续可调等解调关键难题。应用表明,高效调制信号控守能力明显增强,控守时间大大延长,情报生产能力进一步提高,推广应用前景广阔。     

Synthesis of quasi-optimal digital phase-locking systems under the action of additive noises

Quasi-optimal synthesis of digital phase-locking systems (PLSs) is discussed to evaluate the information parameters of a frequency-modulated signal. An adaptive Kalman filter capable of functioning without a priori data on the statistical characteristics of input and test noises is employed. The model of the process under study is identified using the linear trend modified by the self-organization algorithm. Procedures and the results of numerical calculations are presented for the digital system of phase synchronization.     

2FSK信号的相关解码算法

给出了一种基于短时循环自相关特性的2FSK信号快速解码算法。该算法具有抗干扰性能好、编程简单、计算量少、信号动态范围大、便于用DSP芯片实现等优点。用此算法设计的系统实时解调8路2FSK信号，实地入网运行效果良好。文中对相关解码算法运用中的有关问题进行了讨论。     

Optimal power allocation for cognitive radio under interference outage constraint

Cognitive radio is able to share the spectrum with primary licensed user, which greatly improves the spectrum efficiency. We study the optimal power allocation for cognitive radio to maximize its ergodic capacity under interference outage constraint. An optimal power allocation scheme for the secondary user with complete channel state information is proposed and its approximation is presented in closed form in Rayleigh fading channels. When the complete channel state information is not available, a more practical transmitter-side joint access ratio and transmit power constraint is proposed. The new constraint guarantees the same impact on interference outage probability at primary user receiver. Both the optimal power allocation and transmit rate under the new constraint are presented in closed form. Simulation results evaluate the performance of proposed power allocation schemes and verify our analysis.     

数字信号处理及DSP芯片的发展前景

简要介绍了DSP的设计流程及其实现方法,着重介绍了DSPs芯片结构特点、运算速度、应用与市场,并展望了DSPs芯片的发展前景。     

Micro-vibration parameters fast demodulation algorithm and experiment of self-mixing interference

Self-mixing interference （SMI） technique can be used for measuring vibration, displacement, velocity and absolute distance. In this paper, a simple demodulation algorithm for fast measuring frequency and amplitude of a simple harmonic vibration target is proposed based on the basic theoretical model of self-mixing interference effects. The simulative results show that the error between the vibration parameters which are demodulated by this algorithm and initial settings merely results from the sample rate. Further, the experimental system of self-mixing vibration measurement is built. The experimental results have a good agreement with simulation analyses. The maximum error of frequency demodulation is less than 1 Hz in our experiment.     

一种三维调制信号快速解调新方法

根据三维调制信号的特性,提出了一种新的三维调制信号的快速解调方法。该方法基于MUSIC算法,首先利用单次快拍来建立阵列数据的协方差矩阵,然后根据调制信号的先验信息对所得信号空间谱进行判决,来估计其极化辅角与极化相位角等信息,从而恢复出基带信号。分析与仿真结果表明,所提方法不仅可以避免谱搜索,大大降低MUSIC方法的运算量,而且适用于瞬时信号和快速运动信号的解调。     

相位敏感OTDR系统的信号解调方法

提出了一种改进的关于相位敏感光时域反射计(OTDR)系统的信号解调方法.从理论上阐述了该方法的原理,分析了该方法中关键参数(平均次数、滑动窗口和相减间隔)的取值对相位敏感OTDR系统信号处理结果的影响,并且总结了它们取值的指导依据。与常规的数字平均方法对比,利用该方法进行数据处理,有效地解调出扰动信号,进一步说明该方法的可行性.结果表明,该方法根据信号的波动特征将原始数据进行分组,提高了各组数据的相关性,从而明显改善了系统的信噪比,对长距离相位敏感OTDR系统性能的优化有一定的指导意义.     

一种新的FBG传感信号解调技术研究

在基于当前FBG传感信号解调技术的基础上,提出了基于可调谐法布里一珀罗(F-P)滤波法和非平衡马赫一曾德尔(M-z)滤波法的FBG解调方法,并进行了系统仿真模型的设计,对其仿真结果与单独的可调谐F-P滤波法和非平衡M-z滤波法的仿真结果进行了比较.结果表明这种方法的性能得到了明显的提高,适用于FBG传感信号的静态和动态解调.