A NEW METHOD OF BISPECTRAL ESTIMATION FOR TRANSIENT SIGNAL

Estimation of model parameter for transient signal is very important in many aspects. This paper presents a new Markov ARMA model Q-slice estimation algorithm for transient signal based on bispectrum. Simulation results show that this new method has some special features, such as higher estimation precision, lower amount of calculation, higher fitting effect even in lower signal-to-noise ratio (SNR) situation.     

Optimum waveform signal sets with amplitude and energy constraints

It is desirable to choose the waveforms making up a signaling alphabet so that they are maximally separated one from another. This problem is considered, in the space of square-integrable functions, for signals which have finite duration, and are constrained in the ranges of their values as well as in energy. Corresponding to each of the following cases, we establish sharp bounds for the minimum distance and for the average distance between elements of a fixed size signal set, and construct sets of signals that attain both bounds simultaneously. begin{list} item {em Case A (Energy Constraint Only):} The average energy of the waveforms in the signal set is at mostsigma, where0 leq sigma < infty. item {em Case B (Energy and Peak Amplitude Constraints):} The average energy of the waveforms in the signal set isleq sigma (0 leq sigma < 1), and the absolute value of each waveform is at most1. item {em Case C (Energy and Value Constraints):} The average energy of the waveforms in the signal set is at mostb^{2}sigma + a^{2}(1 - sigma), and each waveform takes values in the set[a, b], where0 leq a < b < infty, and0 leq sigma leq 1. end{list} Cases A and B are applicable to signal design for communication in channels with additive noise (say Gaussian), and Case C is applicable to signal design for optical channels, where the signal represents the intensity of a photon stream. The general character of the results is that the minimum distance behaves likegamma sigmain Cases A and B, and likegamma sigma (1 - sigma)in Case C, withgammaa suitable constant.     

Transmission of information masked with an irregular signal via a radio channel

A scheme for transmission of information masked with an irregular signal (chaotic oscillations) is considered. Mathematical models are developed for communications systems in which chaotic oscillations are radiated in two frequency bands separated owing to mixing of regular and chaotic oscillations. Results of numerical analysis and physical experiments are presented. The possibility of confidential transmission of an information signal is demonstrated.     

Quasi-coherent algorithmic demodulator with information signal frequency tuning

The structure is proposed of an algorithmic demodulator for receiving a phase-shift information signal.     

Design of a spread-spectrum modulation signal bearing directional information

In this article, we propose a multiple beams spread-spectrum modulation signal transmitted by a Cassegrain antenna for communication and direction-finding applications. The main idea is that a sum beam and two difference beams are transmitted by the Cassegrain antenna similar to the Monopulse technique. According to the beams’ radiation pattern, a multiple beams spread-spectrum modulation scheme is designed to modulate the beams’ spatial parameters into the transmit signal constellation. In this way, a receiver with a single antenna demodulates the data information and the directional information from the receive signal constellation, simultaneously. Simulation results show that the proposed signal can be applied to the integrated system of communication and direction-finding in a low signal-to-noise ratio environment.     

WDM网状网中考虑传输损伤的动态波带交换算法

针对光信号在传输中受到的自发辐射噪声和偏振模色散两种损伤,提出一种考虑信号质量限制的动态波带交换(DWS-SQC)算法.该算法在保证信号传输质量要求前提下,最小化可选路径端12占用数和减少路径所经总链路数.不同负载动态业务下的仿真研究表明:DWS-SQC既考虑了网络中信号损伤的影响,又有利于网络负载均衡和提高全网端口利用率,可以降低全网阻塞率.     

On optimal signal sets for digital communications with finiteprecision and amplitude constraints

The maximum data rate that can be reliably communicated given a linear, time-invariant, dispersive channel, a receiver that samples the channel output to within an accuracy of ±d where d >0, and a transmitter with an output amplitude constraint is evaluated. For any dispersive channel the maximum rate depends on d and is finite. The transmitted waveforms must be designed so that two channel outputs associated with two distinct transmitted signals are separated in amplitude at a particular time by d. It is shown that given any channel impulse response with rational Laplace transform, there exists an optimal sets of inputs that are ±A everywhere where A is the maximum allowable amplitude. Furthermore, in any finite time interval, each input changes sign a finite number of times. If the channel impulse response is a single decaying exponential, it is shown that simple binary signaling, in which A or -A, depending on the current message bit, is transmitted during each symbol interval, maximizes the data rate     

Zero-crossing information for signal reconstruction

The letter attempts to find the number of derivatives whose zero-crossing information would be necessary for a satisfactory signal reconstruction. A method is obtained which shows that the number of terms considered of the Maclaurin-series expansion of the autocorrelation function is equal to half the number of derivatives used for the zero-crossing information.     

On the use of a priori information for sparse signal approximations

Recent results have underlined the importance of incoherence in redundant dictionaries for a good behavior of decomposition algorithms like matching and basis pursuit. However, appropriate dictionaries for a given application may not be able to meet the incoherence condition. In such a case, decomposition algorithms may completely fail in the retrieval of the sparsest approximation. This paper studies the effect of introducing a priori knowledge when recovering sparse approximations over redundant dictionaries. Theoretical results show how the use of reliable a priori information (which in this paper appears under the form of weights) can improve the performances of standard approaches such as greedy algorithms and relaxation methods. Our results reduce to the classical case when no prior information is available. Examples validate and illustrate our theoretical statements. EDICS: 2-NLSP.     

Capacity and reliability function for small peak signal constraints

The capacity and the reliability function as the peak constraint tends to zero are considered for a discrete-time memoryless channel with peak constrained inputs. Prelov and van der Meulen (1993) showed that under mild conditions the ratio of the capacity to the squared peak constraint converges to one-half the maximum eigenvalue of the Fisher information matrix and if the Fisher information matrix is nonzero, the asymptotically optimal input distribution is symmetric antipodal signaling. Under similar conditions, it is shown in the first part of the paper that the reliability function has the same asymptotic shape as the reliability function for the power-constrained infinite bandwidth white Gaussian noise channel. The second part of the paper deals with Rayleigh-fading channels. For such channels, the Fisher information matrix is zero, indicating the difficulty of transmission over such channels with small peak constrained signals. Asymptotics for the Rayleigh channel are derived and applied to obtain the asymptotics of the capacity of the Marzetta and Hochwald (1999) fading channel model for small peak constraints, and to obtain a result of the type of Medard and Gallager for wide-band fading channels     

Entropy-like distance driven fuzzy clustering with local information constraints for image segmentation

To improve the anti-noise ability of fuzzy local information C-means clustering, a robust entropy-like distance driven fuzzy clustering with local information is proposed. This paper firstly uses Jensen-Shannon divergence to induce a symmetric entropy-like divergence. Then the root of entropy-like divergence is proved to be a distance measure, and it is applied to existing fuzzy C-means (FCM) clustering to obtain a new entropy-like divergence driven fuzzy clustering, meanwhile its convergence is strictly proved by Zangwill theorem. In the end, a robust fuzzy clustering by combing local information with entropy-like distance is constructed to segment image with noise. Experimental results show that the proposed algorithm has better segmentation accuracy and robustness against noise than existing state-of-the-art fuzzy clustering-related segmentation algorithm in the presence of noise.     

The information content of MR images

The theoretical information content, defined by C.E. Shannon (1948), is proposed as an objective measure of MR (magnetic resonance) image quality. This measure takes into account the contrast-to-noise ratio (CNR), scan resolution, and field of view. It is used to derive an optimum in the tradeoff problem between image resolution and CNR, and as a criterion to assess the usefulness of high-resolution (512(2)) MR images. The result tells that for a given total acquisition time, an optimum value of the resolution can be found. This optimum is very broad. To apply Shannon's theory on information constant to MR images, a model for the spatial spectral power density of these images is required. Such a model has been derived from experimental observations of ordinary MR images, as well as from theoretical considerations.     

Hidden information transmission with the use of the delay effect for formation of a masking signal and separation of transmitted oscillations from this signal

A mathematical model illustrating the method for masking regular oscillations in a transmitter is considered. The method is based on mixing these oscillations with chaotic motions formed from pulse chaotic oscillations with the use of the delay effect. Separation of the transmitted signal in a subtractor is also based on the delay effect. Results of numerical analysis are presented. It is shown that the proposed method of transmission and separation of the useful signal provides for the application of developed chaotic oscillations for masking. Transmission of a masked regular signal is experimentally demonstrated in the decimeter wavelength range. Transistor-coupled oscillators with chaotic dynamics are used for generation of noise-like oscillations. Results of experimental studies on formation of continuous noise-like oscillations from pulse noise on the basis of the delay effect are presented for the case when one of the two series of pulses contains the transmitted regular signal. Oscillation filtering is used along with the delay effect for separation of useful oscillations.     

激光制导信号编码信息识别技术

有源干扰作为一种积极有效的干扰手段,使制导武器在攻击阶段收到大量的干扰激光信号而失去正确的目标信息,达到保护重点目标的目的。如何准确地对来袭激光武器激光信号编码信息实时分析与识别,已成为激光对抗的首要任务。在分析现有激光编码和波门设置特点的基础上,结合激光制导信号的时间相关特征,提出了一种基于自相关的激光制导信号脉冲编码信息识别技术,通过仿真、实验对该技术进行了研究,结果表明:该方法有效地解决了在尽可能短的时间内精确复制敌方激光编码的难题,为对抗的实施赢得了宝贵的时间,具有一定的理论和军事应用价值。     

A robust STAP approach for airborne FDA radar with multiple possible prior information constraints

In frequency diverse array (FDA) space–time adaptive processing (STAP) system, the spectrum of fast-moving target is non-well focused in the spatial–temporal plane, which causes a large mismatch between the actual and presumed target steering vector and dramatically degrades the performance of FDA-STAP system. In this paper, we propose a robust FDA-STAP approach based on multiple possible prior information constraints to resolve this issue and improve the performance of FDA-STAP system. In the proposed approach, multiple possible prior information, i.e., multiple large uncertainty regions, where the actual target possibly locate in spatial–temporal domains, are utilized to cover and constraint the estimated steering vector. The multiple uncertainty regions constraints make it possible to accurately estimate the fast-moving target steering vector. Moreover, to mitigate the influence of non-focused spatial–temporal spectrum of fast-moving target, a non-focused constraints is developed using the squared norm of space–time steering vector to avoid the estimated steering vector converge to the non-focused region of fast-moving target. Finally, the proposed robust FDA-STAP is converted into a non-convex quadratically constrained quadratic programming problem, and the semidefinite relaxation technique is employed to obtain the estimated target steering vector. Numerical results indicate that the proposed method has superior performance than other methods, including well-maintained main beam direction and significant performance improvement.

     

A content addressable distributed logic memory with applications to information retrieval

This paper describes a content addressable memory system in which logic is distributed throughout the system. The memory is made up of cells. Each cell is a small finite-state machine which can communicate with its neighbors. These cells are controlled through a set of programming commands. The application of this memory to several problems related to information retrieval is discussed.     

A method of obtaining signal components and their power content ofa residual carrier signal

A novel algorithm for obtaining all signal components of a residual carrier signal with any number of channels is presented. The phase modulation type may be NRZ-L or split phase (Manchester). The algorithm also provides an easy way of obtaining the power contents of the signal components. Steps for recognizing the signal components that influence the carrier tracking loop and the data tracking loop at the receiver are given