信号计资理论模式简析

1信号系统计资理论提出的依据1.1 2001年电务工作会议提出,为适应通信重组,网运分离的要求,要研究一套科学合理的清算办法。由于信号系统按现行换算道岔组清算已完全不适应铁路信息化形势发展需要,必须研发新的清算办法来适应运营管理模式改革发展的需要。

地铁信号计轴系统的故障检修浅述

本文首先分析了地铁信号计轴系统概述,同时阐述了地铁信号计轴系统的故障检修,后总结了全文,仅供参考。

一种用于估计微弱信号之间延时的新方法

在很多检测与估计问题中,接收系统所得到的信号不仅在能量幅度上是微弱的,而且信噪比也是很小的。本文提出了一种在干扰噪声很强的情况下,仍能准确地估计出接收信号间时延的方法。该方法基于自适应噪声抵消器,在其收敛时,用权系数进行内插估计。与传统的用采样函数内插不同,本方法采用五点平滑后的二次内插估计法,既保证了准确度,又较易实现。并得到了实验的验证。

微机计轴道口信号设备

介绍了自行研制的微机计轴道口信号设备的系统构成。

越南宣光水电站机组压水调相系统及其试验浅析

介绍了越南宣光水电站水轮发电机组的压水调相系统的设计,并针对现场的实际情况对其系统及电气流程所做的改进进行了总结和分析。重点说明现场试验所遇的问题,所得到的分析结果和解决处理情况。

Analyzing Undersampled Signals Using High Order Ambiguity Function Algorithm

Aim To find an effective and fast algorithm to analyze undersampled signals. Methods\ The advantage of high order ambiguity function(HAF) algorithm is that it can analyze polynomial phase signals by phase rank reduction. In this paper, it was first used to analyze the parameters of undersampled signals. When some conditions are satisfied, the problem of frequency confusion can be solved. Results and Conclusion\ As an example, we analyze undersampled linear frequency modulated signal. The simulation results verify the effectiveness of HAF algorithm. Compared with time frequency distribution, HAF algorithm reduces computation burden to a great extent, needs weak boundary conditions and doesn't have boundary effect.

An Improved Multi-scale Estimation Method of Signal

In this paper an improved multi_scale estimation method of signal is gaven.The detail signals on each scale are further more decomposed with wavelet transform.The subdetail signals and subsmoothing signals are processed with different threshold respectively. The smoothing signals on the coarsest scale are processed with Kalman fitering and reconstructed with the detail signal on each scale.At last the signal estimate value on the original scale is obtained.

ESPRIT-Based Feature Extraction of Helicopter Acoustic Signal

Aim To extract harmonic frequencies of helicopter acoustic signal as features for hel icopter identification. Methods Estimation of signal parameters via rotational invariance techniques(ESPRIT) was selected to extract harmonic frequencies from really measured helicopter acoustic signal and an algorithm based on the SVD TLS was used. Results ESPRIT correctly extracted harmonic frequencies of helicopter using the data of limited length under the variousflight conditions. Conclusion ESPRIT is an effective method of extracting harmonic frequencies and using harmonic frequencies of helicopter acoustic signal to recognize helicopter is feasible.

A Low-Power-Consumption 9bit 10MS/s Pipeline ADC for CMOS Image Sensors

A low-power-consumption 9bit 10MS/s pipeline ADC,used in a CMOS image sensor,is proposed. In the design, the decrease of power consumption is achieved by applying low-power-consumption and large-output-swing amplifiers with gain boost structure, and biasing all the cells with the same voltage bias source, which requires careful layout design and large capacitors. In addition,capacitor array DAC is also applied to reduce power consumption,and low threshold voltage MOS transistors are used to achieve a large signal processing range. The ADC was implemented in a 0.18μm 4M-1 P CMOS process,and the experimental results indicate that it consumes only 7mW, which is much less than general pipeline ADCs. The ADC was used in a 300000 pixels CMOS image sensor.

Top-Down Design of 260k Color TFT-LCD One-Chip Driver ICs

A top-down design methodology is proposed for the design of TFT-LCD one-chip driver ICs,and a 260k color, 176RGB× 220-dot TFT-LCD one-chip driver IC is successfully developed with silicon verification. This IC is a typical mixed-signal VLSI and is implemented by a 0.18μm HV CMOS process. The static power dissipation is about 5mW for 260k color display mode,and the settling time of the output grayscale voltages within 0.2% error is less than 26μs.

An enhanced iterative joint channel estimation and symbol detection algorithm for OFDM systems

For orthogonal frequency division multiplexing (OFDM) wireless communication, the system throughput and data rate are usually limited by pilots, especially in a high mobility environment. In this paper, an enhanced iterative joint channel estimation and symbol detection algorithm is proposed to enhance the system throughput and data rate. With lower pilot power, the proposed scheme increases system throughput firstly, and then the channel estimation and symbol detection proceed iteratively within one OFDM symbol to improve the BER performance. In the proposed algorithm, the original channel estimate of each OFDM symbol is based on the channel estimate of the previous OFDM symbol, thus the variation of the mobile channel is traced efficiently, so the number of pilots in the time domain can be reduced greatly. Besides reducing the system overhead, the proposed algorithm is also shown by simulation to give much better BER performance than the conventional iterative algorithm does.

Geoacoustic inversion for sediments in the South China Sea based on a hybrid inversion scheme

We performed a long range acoustic propagation experiment in the South China Sea(SCS) in November 2004.The environment of the experiment was with an isothermal sound speed profile,where influence of water volume fluctuation was small,meaning that bottom parameters can be well estimated from acoustic signals.We inverted the acoustic parameters of sediment by using a hybrid inversion scheme that combines the matched field processing inversion with Hamilton sediment empirical relationship and transmission loss data.The numerical results show excellent agreement with the experiment data,indicating validity of the inverted parameters.

An innovative detection method of high frequency BPSK signal with low signal-to-noise ratio

Based on chaotic oscillator system, this paper proposes a novel method on high frequency low signal- to-noise ratio BPSK（ Binary Phase Shift Keying） signal detection. Chaotic oscillator system is a typical non-lin- ear system which is sensitive to periodic signals and immune to noise at the same time. Those properties make it possible to detect low signal-to-noise ratio signals. The BPSK signal is a common signal type which is widely used in modern communication. Starting from the analysis of advantages of chaotic, os~.illator system and signal features of the BPSK signal, we put forward a unique method that can detect low signar-to-noise ratio BPSK sig- nals with high frequency. The simulation results show that the novel method can dclct.t low signal-to-noise ratio BPSK signals with frequency in an order of magnitude of l0s Hz, and the input Signal-to-Noise Ratio threshold can be -20 dB.

A NEW THRESHOLD MULTI-PROXY MULTI-SIGNATURE SCHEME

This paper proposes a threshold mult-proxy multi-signature scheme with share verification. In the scheme, a subset of original signers allows a designated group of proxy signers to sign on behalf of the original group. A message m has to be signed by a subset of proxy signers who can represent the proxy group. Then, the proxy signature is sent to the verifier group. A subset of verifiers in the verifier group can also represent the group to authenticate the proxy signature. In other words, some threshold values will be given to indicate the number of persons to represent a group to authorize the signing capability or to sign a message or to verify the proxy signature.

MP-WFRFT and Constellation Scrambling Based Physical Layer Security System

In this paper, a multiple parameters weighted fractional Fourier transform(MPWFRFT) and constellation scrambling(CS) method based physical layer(PHY) security system is proposed. The proposed scheme is executed by two steps. In the first step, MPWFRFT, implemented as the constellation beguiling(CB) method, is applied to change the signal's identity. In the second step the additional pseudo random phase information, regarded as the encryption key, is attached to the original signal to enhance the security. Typically, the pseudo random phase information can be removed effectively by the legitimate receiver. In contrast to the cryptography based encryption algorithms and the conventional PHY secrecy techniques, the main contribution of the proposed scheme is concentrated on the variation in signal's characteristics. Simulation results show that the proposed scheme can prevent the exchanging signal from eavesdroppers' classifi cation or inception. Moreover, the proposed scheme can guarantee the BER performance at a tolerate increasing in computational complexity for the legitimate receivers.

Microphone Array Speech Enhancement Based on Tensor Filtering Methods

This paper proposes a novel microphone array speech denoising scheme based on tensor filtering methods including truncated HOSVD(High-Order Singular Value Decomposition), low rank tensor approximation and multi-mode Wiener filtering. Microphone array speech signal is represented in three-order tensor space with channel, time, and spectrum modes and then tensor filtering model can be designed to process the multiway array data. As to the first method, noise can be reduced through the truncated HOSVD which is a simple scheme in tensor processing. It is more accurate to find the lower-rank approximation of the three-order tensor with Tucker model. Then MDL(Minimum Description Length) criterion is used to estimate the optimal tensor rank in the second method. Further, multimode Wiener filtering approach upon tensor analysis can be considered as the spanning of one-mode wiener filtering. How to take advantages of tensor model to obtain a set of filters is the heart of the novel scheme. The performances of the proposed three approaches are evaluated with objective indexes and listening quality test. The experimental results indicate that the proposed tenor filtering methods have potential ability of retrieving the target signal from noisy microphone array signal and the multi-mode Wiener filtering method provides the best denoising results among the three ones.

RLS channel estimation with adaptive forgetting factor in space-time coded MIMO-OFDM systems

Considering that channel estimation plays a crucial role in coherent detection, this paper addresses a method of Recursive-least-squares (RLS) channel estimation with adaptive forgetting factor in wireless space-time coded multiple-input and multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. Because there are three different forgetting factor scenarios including adaptive, two-step and conventional ones applied to RLS channel estimation, this paper describes the principle of RLS channel estimation and analyzes the impact of different forgetting factor scenarios on the performances of RLS channel estimation. Simulation results proved that the RLS algorithm with adaptive forgetting factor (RLS-A) outperformed that with two-step forgetting factor (RLS-T) or with conventional forgetting factor (RLS-C) in both estimation accuracy and robustness over the multiple-input multiple-output (MIMO) channel, i.e., a wide-sense stationary uncorrelated scattering (WSSUS) and frequency-selective slowly fading channel. Hence, we can employ the RLS-A method by adjusting forgetting factor adaptively to track and estimate channel state parameters successfully in space-time coded MIMO-OFDM systems.

COMBINED TRANSMIT ANTENNA SELECTION AND DETECTION OVER SPATIAL CORRELATED MIMO SYSTEMS

In this paper a method that combines transmit antenna selection and reduced-constellation detection in spatially correlated Multi-Input Multi-Output （MIMO） fading channels is presented. To mitigate the performance degradation caused by the use of antenna selection that is based on correlation among columns, an iterative receiver scheme that uses only a subset of the constellation points close to the expected symbol vahle estimated in the previous iteration is proposed. The size of the subset can adapt to the maximum correlation of the sub-matrix after the simple antenna selection. Furthermore, the error rate performance of the scheme under linear Miniinutn Mean Square Error （MMSE） or Ordered Successive Interference Cancellation （OSIC） for the first run detection and different interleaver lengths is investigated while the transnlit antenna selection is considered. The simulation results show a significant advantage both for implementation complexity and for error rate performance under a fixed data rate.

HIGHLY PRECISE AND FAST COMPUTATION OF THE CONTINUOUS SIGNAL PAR IN OFDM AND DMT SYSTEMS

Two procedures are developed here to compute the Peak-to-Average envelope power Ratio (PAR) of the continuous signal with N subcarriers in the Orthogonal Frequency Division Multiplexing (OFDM) and Discrete MultiTone (DMT) systems. The first one is an accurate computation method for small N, in which the peak of the Instantaneous Envelope Power Function (IEPF) is obtained by solving the roots of a polynomial, a linear sum of a set of Chebyshev polynomials of the first kind and the second kind. The second procedure, called Stepwise Refinement Algorithm (SRA), is a highly precise and fast computation method for arbitrary N by using Inverse Fast Fourier Transform (IFFT), the Chirp Z-Transform (CZT) and a newly introduced relationship between the IEPF peak and its most adjacent oversampled sample.

Study on Design of Interplex Method for GNSS Signal

In order to satisfy sending multi-channel navigation signals in one frequency for modern GNSS（Global Navigation Satellite System）, the principle of Interplex multiplexing were introduced. And the three-way multiplexing structure and the four-way multiplexing method were also optimized. The Galileo E1 signal, as the example of Interplex reuse, was analyzed in detail. The power configuration of the multiplexing efficiency and the minimum of the multiplexing efficiency were obtained.