A new noise erosion operator for anisotropic diffusion

A noise erosion operator based on partial differential equation (PDE) is introduced, which has an excellent ability of noise removal and edge preservation for two-dimensional (2D) gradient data. The operator is applied to estimate a new diffusion coefficient. Experimental results demonstrate that anisotropic diffusion based on this new erosion operator can efficiently reduce noise and sharpen object boundaries.     

一种具有自适应特性的SSO噪声抑制输出驱动电路

介绍了SSO噪声产生的原因,简要概述了常用的抑制SSO噪声的方法.在此基础上,提出了一种具有自适应特点的SSO噪声抑制输出驱动电路,并给出了较详细的分析和比较.     

Switching degenerate diffusion PDE filter based on impulselike probability for universal impulse noise removal

In this paper, a switching degenerate diffusion partial differential equation filter (SDDPDE) is developed by introducing the switching operators for reducing all kinds of impulse noise, and especially for images having a mixture of salt-and-pepper impulse noise and random-valued impulse noise which is a shortage for most of the existing filtering models. Our SDDPDE consists of the coarse and fine filtering stages. In the coarse filtering stages, the switching operator depends on a simple noise detector. In the fine filtering stages, we introduce the notion of impulselike probability, and the switching operator depends on both a simple noise detector and impulselike probability. Our SDDPDE will denoise noise pixels detected by the coarse detector while further modify the so-called noise-free pixels according to impulselike probability. The main advantages of our SDDPDE over published approaches are its simplicity and universality. In addition, we demonstrate the performance of our SDDPDE via application to three standard test images, corrupted by salt-and-pepper impulse noise, random-valued impulse noise and mixed impulse noise with high-noise levels, and the comparison with the other well-known filters. Experimental results show that our SDDPDE achieves high peak signal-to-noise ratio and better visual effect.     

Wavelet-based Rician noise removal for magnetic resonance imaging

It is well known that magnetic resonance magnitude image data obey a Rician distribution. Unlike additive Gaussian noise, Rician "noise" is signal-dependent, and separating signal from noise is a difficult task. Rician noise is especially problematic in low signal-to-noise ratio (SNR) regimes where it not only causes random fluctuations, but also introduces a signal-dependent bias to the data that reduces image contrast. This paper studies wavelet-domain filtering methods for Rician noise removal. We present a novel wavelet-domain filter that adapts to variations in both the signal and the noise.     

A new adaptive recursive RLS-based fast-array IIR filter for active noise and vibration control systems

Infinite impulse response filters have not been used extensively in active noise and vibration control applications. The problems are mainly due to the multimodal error surface and instability of adaptive IIR filters used in such applications. Considering these, in this paper a new adaptive recursive RLS-based fast-array IIR filter for active noise and vibration control applications is proposed. At first an RLS-based adaptive IIR filter with computational complexity of order O(n²) is derived, and a sufficient condition for its stability is proposed by applying passivity theorem on the equivalent feedback representation of this adaptive algorithm. In the second step, to reduce the computational complexity of the algorithm to the order of O(n) as well as to improve its numerical stability, a fast array implementation of this adaptive IIR filter is derived. This is accomplished by extending the existing results of fast-array implementation of adaptive FIR filters to adaptive IIR filters. Comparison of the performance of the fast-array algorithm with that of Erikson’s FuLMS and SHARF algorithms confirms that the proposed algorithm has faster convergence rate and ability to reach a lower minimum mean square error which is of great importance in active noise and vibration control applications.     

A soft-constrained recursive-like adaptive noise canceller

The adaptive adjustment algorithm for a prior art recursive-like noise canceller must incorporate a constraint that prevents convergence to the useless trivial solution. This constraint can also prevent convergence to the best attainable solution. An alternative to the prior-art hard-constrained recursive-like canceller, that "softens" the constraint by making it adaptive, is proposed.     

Edge preserving adaptive anisotropic diffusion filter approach for the suppression of impulse noise in images

This paper proposes a new anisotropic diffusion approach to remove the impulse noise and retain the fine details. The proposed approach contains two stages, the first stage detects the impulse noise, and the second stage removes the noisy pixel and retains the fine details of the original image. The Laplacian operator is used to fine-tune the image quality of the restored image in the anisotropic diffusion filter. The proposed approach is tested with PSNR, IEF, correlation factor, and NSER for different test images and the results are compared against existing algorithms. The simulation results show that the proposed approach gives better results than the existing denoising algorithms.     

A new method to derive white matter conductivity from diffusion tensor MRI

We propose a new algorithm to derive the anisotropic conductivity of the cerebral white matter (WM) from the diffusion tensor MRI (DT-MRI) data. The transportation processes for both water molecules and electrical charges are described through a common multicompartment model that consists of axons, glia, or the cerebrospinal fluid (CSF). The volume fraction (VF) of each compartment varies from voxel to voxel and is estimated from the measured diffusion tensor. The conductivity tensor at each voxel is then computed from the estimated VF values and the decomposed eigenvectors of the diffusion tensor. The proposed VF algorithm was applied to the DT-MRI data acquired from two healthy human subjects. The extracted anisotropic conductivity distribution was compared with those obtained by using two existing algorithms, which were based upon a linear conductivity-to-diffusivity relationship and a volume constraint, respectively. The present results suggest that the VF algorithm is capable of incorporating the partial volume effects of the CSF and the intravoxel fiber crossing structure, both of which are not addressed altogether by existing algorithms. Therefore, it holds potential to provide a more accurate estimate of the WM anisotropic conductivity, and may have important applications to neuroscience research or clinical applications in neurology and neurophysiology.      

Bit error rate for 4-DPSK in fast Rician fading and Gaussian noise

A closed-form expression for the bit error rate of 4-DPSK in fast Rician fading and white Gaussian noise is presented. This expression is a supplement to an already known formula for the symbol error rate of MDPSK, which can be evaluated only by numerical integration     

A generalized expression for diffusion noise and hot electron noise at arbitrary drift velocities

It is demonstrated that the usual form of Nyquist's theorem, extended to include hot electron effects, is valid for arbitrary drift velocities in nondegenerate semiconductors. The same is true for the expression for diffusion noise if the diffusion constant is properly defined from a “spread in drift” experiment.     

基于自适应滤波与非线性谱相减算法的联合降噪技术研究

讨论了在强噪声环境下将自适应滤波算法与非线性谱相减算法相结合的语音增强方法。仿真结果表明,在大大消除背景噪声的同时,该方法还有效地抑制了“音乐噪声”,运算量小,适用于强噪声环下的有声／无声检测。     

A stable two-stage recursive-like adaptive noise canceller

An approach to the realization of a recursive-like adaptive noise canceller that employs only nonrecursive adaptive filters is presented. This approach is an alternative to prior art that has the advantage of guaranteed stability, but the disadvantage of residual signal distortion.     

A new design for digital adaptive filters

The design and operation of a digital adaptive filter based on a modified Widrow-Hoff algorithm is described. It uses LSI components as main elements. This filter realization converges faster than other realizations reported hitherto because its weight vector is updated at every sampling instant.     

A new structure for adaptive broad-band beamforming

The performance characteristics of adaptive array systems with derivative constraints have been investigated by several authors. As a result of the derivative constraints, the array beamwidth in the look direction could be made as broad as desired; however, this increased beamwidth was achieved at the price of reducing array gain. A structure is proposed for an adaptive broadband beamforming system in a manner that can produce a broader beamwidth in the look direction without any derivative constraints imposed on the adaptive processor. Compared to the conventional Frost beamformer with derivative constraints, the computer simulations illustrate the effectiveness of the proposed structure, which broadens the beamwidth in the look direction with only slight sacrifice of array gain     

一种有效的片上系统串扰估计模型

目前,片上系统(SOC)的制造技术已经进入了深亚米时代,然而片上系统内部信号传输线发生串扰而导致系统功能失效的可能性却大大增加了.在这种情况下,对串扰进行估计就显得十分重要.本文针对已有Devgan串扰模型的不足,提出了一种简单有效的串扰估计模型,并对该模型的估计效果和HSPICE的仿真结果进行了比较.     

Improved tracking adaptive noise canceler for nonstationaryenvironments

The performance of multiple reference adaptive noise cancelers is investigated and a new filter structure is proposed that provides better tracking in the multipath, multisource, nonstationary automobile noise environment studied. The filter uses the least mean square (LMS) algorithm with multiple filtering stages and subbanded sections to improve the overall tracking performance while maintaining filter stability     

Cascade configurations for recursive-like adaptive noise cancellation

Two novel recursive-like two-stage adaptive noise cancellers that circumvent the requirement, in prior art one-stage recursive-like cancellers, of incorporating a constraint on filter coefficients, are presented. These novel two-stage cancellers are based on a cascade configuration, rather than the prior art parallel configuration. For applications in which even a small amount of signal distortion is intolerable, a third novel two-stage noise canceller that guarantees distortion-free performance is presented. Finally, a multistage cascade configuration that has the potential for distortion-free, high-performance noise cancellation is presented.     

Difference-type noise detector for adaptive median filter

Noise detection-based median filters have been widely applied to impulse noise reduction. However, the number of pixels misclassified is obviously increased in high noise density. To overcome such drawback, a difference-type noise detector is proposed. In image filtering, a noise detection-based adaptive median algorithm is presented. Experimental results show that the proposed filter can well remove the impulse noise and preserve more details of original images.     

A new method for on wafer noise measurement

A method for measuring the noise parameters of MESFETs and HEMTs is presented. It is based on the fact that three independent noise parameters are sufficient to fully describe the device noise performance. It is shown that two noise parameters, R_n and |Y_OPT|, can be directly obtained from the frequency variation of the noise figure F₅₀ corresponding to a 50 Ω generator impedance. By using a theoretical relation between the intrinsic noise sources as additional data, the F₅₀ measurement only can provide the four noise parameters. A good agreement with more conventional techniques is obtained