Wang Shuxun

An adaptive block-based blind watermarking algorithm

In this paper we propose an adaptive block-based blind watermarking algorithm using DWT. By analyzing the characteristic of detail subband coefficients of the image after discrete wavelet transform, we use the mean and variance of the detail subbands to modify the wavelet coefficients adoptively to embed the watermark. This is a blind watermark algorithm to confirm the copyright without the original image and the watermark is a meaningful binary image. The experimental results and attack analysis show that the proposed algorithm is effective and robust to common image processing operations and some geometric attacks, such as JPEG/JPEG2000 lossy compression, additive noise, cropping, pixel-shift, and so on.

Adaptive denoising based on wavelet thresholding method

The paper presents a novel adaptive denoising method based on a wavelet thresholding method. First, it presents a new thresholding function that has a continuous derivative while the derivative of a standard thresholding function is not continuous. The new thresholding function makes it possible to construct an adaptive algorithm based on the wavelet thresholding method. Second, by using the new thresholding function, the paper presents an adaptive method based on SURE (Steins unbiased risk estimate) risk. Finally, several numerical analysis examples are given; the results show that the proposed method is very effective in finding the optimal solution in the mean square error (MSE) sense. It also indicates that this method gives better MSE performance than other wavelet thresholding methods.

Chirp signal analysis based on PWD in fractional Fourier transform domain

A new pseudo Wigner distribution (PWD) in the fractional Fourier transform (FT) domain is proposed to analysis single or multi-component chirp signals. A rotated short-time Fourier transform (STFT) is used to realize the proposed distribution, and the appropriate fractional domain is found from the knowledge of second-order fractional FT moments. By analyzing the signal in the most appropriate fractional domain, the proposed time-frequency distribution preserves the WD auto-terms and cancels the cross-terms when there are several signal components. The proposed method is easy to be performed without the significant additional computational costs. Simulation results confirm a qualitative advantage in the time-frequency representation, when the calculation is done in the optimal fractional domain.

A blind watermarking algorithm based on DWT for color image

The work concerns with the watermarking algorithm that embeds binary image data invisibly into a color image based on discrete wavelet transform (DWT). The original color image is transformed into the YUV color space. Exploiting the excellent properties of the wavelet transform, we use the mean and variance of the detail subbands to modify the wavelet coefficients adaptively to embed the watermark. This is a blind watermark algorithm to confirm the copyright without the original image and the watermark is a meaningful binary image. The experimental results show that the watermarks are invisible and robust against noise and commonly image-processing methods, such as JPEG/JPEG2000 lossy compression, Gaussian noise, salt-pepper noise, cropping, pixel-shift, and so on.

The chaotic characteristics of transistor noise at low frequency

For a long time, people have described the transistor noise at low frequency with the theory of random process. In this paper, based on reconstructing phase space of the transistor EN noise time series, the nonlinear dynamic parameters are studied. The results of our study demonstrated that the transistor EN noise at low frequency has a limited fractional dimension, besides that, the largest Lyapunov exponent of the transistor EN noise is positive, so we can draw the conclusion that the transistor EN noise at low frequency has some chaotic characteristics.

Multipath time delay estimation with unknown spatially correlated noise and multiple access interference using cyclic statistics

Multipath time delay estimation based on cyclic correlation parametric approach is proposed in this paper. Multipath time delays are estimated precisely, and non-stationary multiple access interference and spatially correlated noises can be suppressed effectively by the use of this new approach. This approach has better performance than the time delay estimation based on correlation and the higher-order cumulants approaches. The relative conclusion are given and verified by the simulation experiments.

Double exponential model of ultrasonic signals

The notion of representing discrete-time ultrasonic signals using double exponential model and the method of computing modelpsilas parameters using Prony method are introduced. The rise time tr and full width half maximum tfwhm of double exponential model is discussed and contrasted with the damped exponential model. It is shown that flexibility of double exponent model is superior to damped exponential model. Fitting the measured data and simulation of TOA (Time-Of-Arrived) proved that the double exponent model has better performance than the damped exponential model.

2-D DOA estimation in the presence of Gaussian noise with quaternion

In this paper, quaternion was introduced in estimating azimuth and elevation of two dimensional direction of arrival (2-D DOA). We proposed a new quaternion signal model instead of classical complex signal model. Then, two definitions of multiplicative rules of quaternion were introduced. At last, we drew out azimuth and elevation using two definitions of quaternion and isomorphic complex expression of Hamiltons quaternion. Some simulations illustrated this new idea

An Algorithm for Near Field Source Localization Based on Multistage Wiener Filters

A method for near field source parameter estimation based on multistage Wiener filters is proposed in this paper. The presented method does not require the formation of the covariance matrix and its eigendecomposition or singular value decomposition in the near field source localization, thereby having the advantage in precision and computational complexity. Some simulation examples show the validity of this algorithm

Estimating frequencies of two dimensional harmonics with extended quaternion matrix pencil

In this paper, we proposed a novel algorithm to estimate frequency pairs of two dimensional harmonics, whose frequency pairs might share the common frequency. First, we presented a new math model of two dimensional harmonics signal, which was based on quaternion. Then, we presented operation rules definitions of Hamiltons quaternion and Mas quaternion. After analyzing the properties of two kind of quaternion, we computed correlation function of quaternion data model using Mas operation rules and constructed extended quaternion matrix of correlation function data. At last, we proposed our estimation method using Hamiltons operation rules. Some simulations illustrated our idea.