一种双频激光干涉信号探测器的设计

为了获取高精密双频激光干涉测量中的干涉信号,完成了一种新的光电探测器电路设计。该探测器利用AD645设计了精密低噪声光电转换前置放大器,保证微弱干涉光信号的有效接收;增益可调的主放大器设计保证输出信号足够的动态范围,适应不同类型的干涉信号处理电路,双二次型带通滤波器有效抑制了噪声与温漂。结果表明,研制的光电探测器能完成微弱干涉信号的接收处理,信噪比高、频率稳定、结构简单易实现,可应用于高精密比相计等激光干涉仪信号处理装置。     

Optimal choice of intermediate frequency for zero-crossing detectors

It is illustrated that the intermediate frequency (IF) in an IF zero-crossing detector (ZXD) for Bluetooth basic rate transmission affects the transmission quality. A simple optimisation strategy is presented and it is shown that simple IF ZXD structures benefit more from the optimal choice of the IF than hypothesis detectors     

Fast time-invariant implementations of Gaussian signal detectors

A new implementation is presented for the optimum likelihood ratio detector for stationary Gaussian signals in white Gaussian noise that uses only two causal time-invariant filters. This solution also has the advantage that fast algorithms based on the Levinson and Chandrasekhar equations can he used for the determination of these time-invariant filters. By using a notion of "closeness to stationarity,' there is a natural extension of the above results for nonstationary signal processes.     

Stochastic iterative algorithms for signal set design for Gaussianchannels and optimality of the L2 signal set

We propose a stochastic iteration approach to signal set design. Four practical stochastic iterative algorithms are proposed with respect to equal and average energy constraints and sequential and batch modes. By simulation, a new optimal signal set, the L2 signal set (consisting of a regular simplex set of three signals and some zero signals), is found under the strong simplex conjecture (SSC) condition (equal a priori probability and average energy constraint) at low signal-to-noise ratios (SNR). The optimality of the L1 signal set, the confirmation of the weak simplex conjecture, and two of Dunbridge's (1967) theorems are some of the results obtained by simulations. The influence of SNR and a priori probabilities on the signal sets is also investigated via simulation. As an application to practical communication system design, the signal sets of eight two-dimensional (2-D) signals are studied by simulation under the SSC condition. Two signal sets better than 8-PSK are found. Optimal properties of the L2 signal set are analyzed under the SSC condition at low SNRs. The L2 signal set is proved to be uniquely optimal in 2-D space. The class of signal sets S(M, K) (consisting of a regular simplex set of K signals and M-K zero signals) is analyzed. It is shown that any of the signal sets S(M, K) for 3⩽K⩽M-1 disproves the strong simplex conjecture for M⩾4, and if M⩾7, S(M, 2) (the L1 signal set) also disproves the strong simplex conjecture. It is proved that the L2 signal set is the unique optimal signal set in the class of signal sets S(M, K) for all M⩾4. Several results obtained by Steiner (see ibid., vol.40, no.5, p.721-31, 1994) for all M⩾7 are extended to all M⩾4. Finally, we show that for M⩾7, there exists an integer K'相似文献   

Analysis of the performance and sensitivity ofeigendecomposition-based detectors

A new framework is presented for the analysis of the performance of detection methods, such as AIC and MDL, which are based on the eigenvalues of the sample covariance matrix. It is shown that theoretical analysis of the probabilities of overestimation and underestimation can be much more conveniently carried out via a proposed, particularly simple, sequence of statistics. Also, the breakdown of these detection methods in the presence of model nonidealities is explored by theory, simulations, and experimentation with real array data. For example, theoretical arguments are given to demonstrate the high degree of sensitivity of the detectors to unknown deviations of the noise from whiteness     

Non-asymptotic performance analysis of single-cycle detectors

In this paper, a new formulation of the probabilities of detection and false alarm for a class of cyclic-feature detectors known as single-cycle detectors is derived for additive white Gaussian noise channels. As opposed to previously published papers, the formulation derived here is non-asymptotic, being valid for any signal-to-noise ratio value. Additionally, the proposed formulation is general, allowing for the analysis of the singlecycle detection performance for any modulation scheme and any cycle frequency.     

Simulated performance of analog Viterbi detectors

The reasons for pursuing analog implementations of the Viterbi algorithm for detection are presented. Some of the tradeoffs to be considered in choosing an analog architecture are discussed, and a suitable architecture for investigation is given. Simulation results based on the chosen architecture are presented and clearly show that analog implementations of the maximum likelihood sequence detector are worth pursuing. In addition, the simulation results provide quantitative guidelines for establishing the required specifications of the individual circuit blocks required to construct a Viterbi detector     

A performance study of MIMO detectors

Several approaches have recently been proposed for the efficient optimum or approximate solution of the detection problem in multiple-input multiple-output transmission systems. These are, however, difficult to compare. In the present work we briefly summarize the most popular and promising of these approaches and offer a way to visualize the tradeoff between complexity of the detection and the achievable power efficiency using "complexity-power diagrams". We conclude that the so-called sphere decoder algorithm is very attractive in terms of average complexity, while for low and constant processing delay lattice reduction with subsequent simple linear or nonlinear detection is more favorable.     

Asymptotic performance analysis of cyclic detectors

The paper deals with the analytical evaluation of the asymptotic detection and false-alarm probabilities of multicycle and single-cycle detectors operating in additive white Gaussian noise with unknown and nonrandom spectral level, which are based on the cyclostationarity properties of the signal to be intercepted. The receiver operating characteristics are derived by using the asymptotic complex normality and the covariance expression of the sample average estimator of the cyclic covariance in an observed discrete-time series. A numerical example for interception of a binary phase-shift keying signal is considered     

A performance study of some transient detectors

We present a simulation study of several different statistics applied to the detection of unknown transient signals in white Gaussian noise. The results suggest that relatively unsophisticated tests based on temporal localization of power, such as the Page (1954) test and a test based on a new statistic due to Nuttall (see NUWC-NPT Tech. Rep. 11123, 1996, and NUWC-NPT Tech. Rep. 10822, 1997), give reliable results     

Improved operation of m-interval detectors by optimum signal selection

The theory of them-interval partition detector is extended to include the analysis and design of nonconstant signals. Using the derived locally most powerful scores, the performance of this detector is investigated. A discrete formulation is used to select the signal and correlation function of the detector to optimize a performance index that reflects the system constraints. Though the detector appears to be similar to a conventional correlation detector, it retains the robustness properties of them-interval detector. In addition, a method is presented whereby dependent samples may be used while still retaining nonparametric operation of the detector.     

On the performance of digital detectors with dependent samples

The asymptotic performances of three digital detectors operating with dependent samples are examined. Analytic expressions for the performances when the number of dependent samples M is large are obtained. Examples are also given which indicate how the performances vary with M. It is shown that the performances of hard-limiting detectors may be improved by processing more dependent samples. The amount of the hard-limiting loss that is recoverable depends upon the detector prefilter. A simple expression is derived which gives the irretrievable hard-limiting loss as a function of the noise autocorrelation,     

激光导引头四象限探测器偏差信号特性研究

为了分析四象限探测器偏差信号对激光导引头探测定位精度的影响,在激光导引头四象限探测器探测定位原理的基础上,采用计算机建模仿真的方法,研究了入射光斑大小、分划线宽度和背景光强度对四象限探测器偏差信号的影响。结果表明,入射光斑变大,四象限探测器的灵敏度会变低,动态跟踪范围变大;分划线宽度在探测器串扰允许的范围内越窄越好;背景光降低了四象限探测器的灵敏度。该研究结果有助于提高激光导引头四象限探测器探测定位精度。     

Objective measure of performance of voice activity detectors

A method for objectively measuring the subjective quality of speech clipped by voice activity detectors (VADs) is presented. This system is evaluated by comparing the output of a VAD to that obtained from subjective tests. The method is shown to produce an accurate prediction of the mean opinion score (MOS) determined by listening tests     

Microwave signal-to-noise performance of CdSe bulk photoconductive detectors

The microwave signal and noise response of CdSe bulk photoconductive detectors have been measured and compared with that of a high-speed junction photodiode. The signal measurements were made with CW intensity modulated light at 3000 Mc. Excellent quantitative agreement was obtained between the simple photoconductivity theory of direct light demodulation and experiment. At low optical intensities, the observed noise can be accounted for within the framework of existing theories of generation-recombination (GR) noise when the effects of electron retrapping are accounted for. At high optical intensities, nonlinear deviations are observed which can be accounted for only qualitatively. The results demonstrate clearly that such a photoconductor, when used as a simple quantum counter, will always be thermal rather than GR noise limited. Measurements show that the photoconductor as it is usually used in a nonoptimum configuration is some 50 db less sensitive than a good photodiode.     

p-GaAs同质结太赫兹探测器的优化与性能

从提高p-GaAs同质结太赫兹探测器量子效率出发,在考虑温度和偏压等参数的影响后,优化了谐振腔增强的p-GaAs同质结太赫兹探测器的材料及结构参数,使探测器的量子效率提高到了17%.并计算了探测器的响应率、探测率和偏压、温度、光谱频率的关系,得到了最佳工作偏压(10~40 m V)、最佳工作温度(8 K)和最大探测率(4.1×1010cm Hz1/2/W).而通过施加一对匹配的反射镜来构造谐振腔的设计,所能获得的极限量子效率为26%,极限探测率和响应率分别为5.7×1010cm Hz1/2/W、25.9 A/W.     

采用PWM输出提升传感信号调理器性能

目前,大多数硅压阻传感器（PRT）用于压力测量,它们通过应用广泛的微型加工技术进行组装,通常采用4个电阻桥臂构成典型的惠斯通电桥,安装在单芯片。与集成电路类似,由于单个晶片中包含成百上千个传感元件,传感器价格便宜。到目前为止,大多数集成传感器主要用于低精度或中等精度要求的场合,比如汽车、消费电子产品和部分工业应用。     

基于数字信号处理方式读出二元并行CdZnTe探测器输出信号

本文中介绍了二元并行CdZnTe探测器的读出电子线路,特别是用于信号处理的数字电路。结果显示用模拟电路方法测得二元并行探测器的探测效率分别是单元探测器的1.8和2.倍,但能量分辨率被限制了。然而对于能量分辨率的测试结果,数字方法得到的结果比模拟方法得到的好很多,提高了26.67%,同时探测效率却没有见效。导致这一区别的原因文中也做了相应的讨论。