Adaptive digital notch filter design on the unit circle for theremoval of powerline noise from biomedical signals

Investigates adaptive digital notch filters for the elimination of powerline noise from biomedical signals. Since the distribution of the frequency variation of the powerline noise may or may not be centered at 60 Hz. Three different adaptive digital notch filters are considered. For the first case, an adaptive FIR second-order digital notch filter is designed to track the center frequency variation. For the second case, the zeroes of an adaptive IIR second-order digital notch filter are fixed on the unit circle and the poles are adapted to find an optimum bandwidth to eliminate the noise to a pre-defined attenuation level. In the third case, both the poles and zeroes of the adaptive IIR second-order filter are adapted to track the center frequency variation within an optimum bandwidth. The adaptive process is considerably simplified by designing the notch filters by pole-zero placement on the unit circle using some suggested rules. A constrained least mean-squared algorithm is used for the adaptive process. To evaluate their performance, the three adaptive notch filters are applied to a powerline noise sample and to a noisy EEG as an illustration of a biomedical signal     

WTA 2007 - I.3 - Deterministic Adaptive Finite Automata

The investigation of determinism issues in formal adaptive devices is particularly important when designing formal adaptive devices that must exhibit high operation performance. In the special case of adaptive formalisms, there is a serious difficulty related to determinism assurance, since their inherent self-modifying behavior makes it very difficult to assure that determinism is kept throughout the device’s operation. This work formally states the concept of determinism for adaptive finite-state automata, a class of adaptive devices that is particularly important for their relative simplicity. By studying this particular formalism, some generalizations to the adaptive devices were proposed. In addition, a set of requirements that should be satisfied in order to obtain deterministic adaptive finite-state automata were stated and a specific subclass of deterministic adaptive devices was defined.     

WTA 2007 - I.2 - Adaptive Grammars - State of Art of the Applied Research on Adaptive Automata

This article presents a line of research, in adaptive automata, based in results for context-free adaptive grammars with appearance checking. The grammatical results are described and exemplified and a strategy is proposed in order to obtain analogous results for the case of the adaptive automata. This strategy is then applied successfully to deduce a restricted version, for the case of the adaptative automata, of the general result for context-free adaptive grammars with appearance checking.     

Technique of enhancing the noise immunity of broadband communications systems

A technique is considered for enhancing the noise immunity of broadband communications systems with repetition. This technique is based on generating a broadband noise-like signal in the transmitting circuit of the system and adaptive compensation of broadband localized interferences in the receiver. In this case, an adaptive variation of transmitter carriers is conducted in each of the channels. The gain in noise immunity provided by the technique proposed was calculated in comparison with other known techniques.     

Analysis of an over-constrained adaptive array

In antenna arrays, the number of nulls that can be formed independently is equal to or less than the number of array elements minus one. Therefore, if the number of interferences exceeds the number of freedom for pattern synthesis in adaptive arrays, nulls in the radiation pattern can not be steered toward each interference direction. To clarify the behavior of the adaptive array in such an environment, an analysis is made for the case where two interferences are impinging on the two-element directionally constrained adaptive array. As a result, it is proved that the adaptive array acts to reduce the undesired noise power at the array output. However, improvement in output signal-to-noise ratio is insufficient because of the limitation in null formation.     

Analysis of Convergence of a Frequency-Domain LMS Adaptive Filter Implemented as a Multi-Stage Adaptive Filter

We present an analysis of the convergence of the frequency-domain LMS adaptive filter when the DFT is computed using the LMS steepest descent algorithm. In this case, the frequency-domain adaptive filter is implemented with a cascade of two sections, each updated using the LMS algorithm. The structure requires less computations compared to using the FFT and is modular suitable for VLSI implementations. Since the structure contains two adaptive algorithms updating in parallel, an analysis of the overall system convergence needs to consider the effect of the two adaptive algorithms on each other, in addition to their individual convergence. Analysis was based on the expected mean-square coefficient error for each of the two LMS adaptive algorithms, with some simplifying approximations for the second algorithm, to describe the convergence behavior of the overall system. Simulations were used to verify the results.     

A Class of Adaptive Cyclostationary Beamforming Algorithms

One of the main benefits of the cyclostationary beamforming algorithms is their ability to extract signals from co-channel interference with only a knowledge of the cycle frequency. In this paper, we study the popular cyclostationary beamformers, and propose five new algorithms, namely, the adaptive cyclic adaptive beamforming (ACAB), adaptive cross-SCORE (ACS), constrained least-squares (CLS), adaptive phase-SCORE (APS), and maximal constrained autocorrelation (MCA) algorithms. All these algorithms are adaptive and have a computational complexity of O(n ²) complex multiplications, where n is the number of array elements. A comparative study of these algorithms is made based on numerical simulations. Each of these algorithms has specific application scenarios. The ACS and the APS algorithms are particularly suited for very adverse signal environments. The ACAB, MCA and cyclic adaptive beamforming (CAB, from the work of Wu and Wong) algorithms can provide good performance in the case of medium or weak interference, while the CLS algorithm is especially suitable for weak interference. The CAB algorithm is shown to be a special case of the least-square self-coherent restoral (LS-SCORE) algorithm. Some insights as to how one can assign carrier frequency and symbol rate during digital modulation are also suggested. The proposed adaptive algorithms are easy to implement, and thus are very promising for applications in wireless and mobile communications. This work was supported by the NSERC of Canada.     

自适应SAR图像边缘检测算法

边缘检测是图像分析的基础,在对SAR图像进行边缘检测时,由于SAR图像存在很强的相干乘性斑点噪声,几乎没有一种方法既能有效地检测边缘又能排除斑点噪声的影响而不产生较多的虚假边缘,特别是在低视数SAR的情况下,该文指出了在低视数情况下应当如何对Touzi ratio边缘检测方法和最大似然(ML)边缘方法的检测窗口进行改进,在对SAR图像进行边缘检测时,引入了自适应窗口的方法,并将其应用到Touzi ratio边缘检测和最大似然 (ML)两个恒虚警边缘检测算法中,取得了很好的改进效果,引入自适应窗口的方法也适用于其它的SAR图像边缘检测算法。     

Distributed uplink scheduling and rate control in cdma2000 using adaptive antenna arrays

Distributed uplink scheduling and rate control in CDMA networks are considered in the case of adaptive antenna arrays present at the base station. The system model with omnidirectional antennas is generalized to the case where adaptive antenna arrays are deployed. Rate control in a probabilistic manner is investigated. Long-term control by the base station through token bucket constraints is incorporated in the system. Monte Carlo simulation results show considerable improvement when adaptive antenna arrays are used. Optimization of the rate transition probabilities is treated in the special case of on–off scheduling.     

Simultaneous nulling in the sum and difference patterns of a monopulse antenna

Most adaptive array research has not directly addressed the problem of nulling in a monopulse antenna. Placing a null in the sum does not automatically place a null in the difference pattern and vice versa. Nulls may be placed in the two patterns with the use of separate adaptive weights and controls for the sum and difference channels. However, this requires two sets of adaptive hardware for one antenna. A technique for simultaneous hulling in the sum and difference channels of a monopulse phased array using one set of adaptive weights shared by both channels is described. First, the technique is described for amplitude and phase nulling, then for phase only hulling. In each case, the ability to simultaneously null in both channels with one set of variable weights is theoretically demonstrated.     

双基地机载预警雷达空时自适应处理方法

本文在文献[1] 所建杂波模型的基础上,进一步研究空时自适应处理对双基地机载预警雷达杂波的抑制问题.深入分析了双基地机载预警雷达杂波距离多普勒特性,进而提出了一种基于距离多普勒补偿的空时二维自适应处理方法.理论分析与计算机仿真表明,该算法能有效实现工作于低重频时双基地机载预警雷达杂波抑制.     

An energy-based adaptive control design technique for multibody-mechanisms with flexible links

In this article, an adaptive control design technique for multibody mechanisms is proposed and described in detail for the case of a planar four-bar flexible-link mechanism. The controller is obtained by superposing a PD position controller, an adaptive proportional vibration controller, and, when the effects of gravity cannot be neglected, an additional term that compensates the (equivalent) gravity torque. The controlled system simple stability is formally proved by means of a model-independent energy-based approach, whereas asymptotic stability is discussed only for the case when no gravity effect needs to be accounted for. The controller performances are tested in simulation in both cases.     

Supervised learning sequential structure and parameter adaptive pattern recognition: Discrete data case (Corresp.)

In a previous paper [1], Bayes-optimal recursive supervised learning structure and parameter adaptive pattern recognition systems were derived for continuous "lumped" Gaussian processes. In this paper, the discrete data case is considered, and the discrete data version of the partition theorem is derived. Several examples are also presented of the application of the adaptive detectors, and computational results are given indicating their learning capacity and convergence rate.     

A generic applied evolutionary hybrid technique

In this contribution, a generic applied evolutionary hybrid technique that combines the effectiveness of adaptive multimodel partitioning filters and genetic algorithm (GAs) robustness has been designed, developed, and applied in real-world adaptive system modeling and information mining problems. The method can be applied to linear and nonlinear real-world data, is not restricted to the Gaussian case, is computationally efficient, and is applicable to online/adaptive operation. Furthermore, it can be realized in a parallel processing fashion, a fact that makes it amenable to very large scale integration (VLSI) implementation.     

直接序列扩频通信中干扰抑制的进化规划自适应非线性滤波技术

进化规划（ＥｖｏｌｕｔｉｏｎａｒｙＰｒｏｇｒａｍｍｉｎｇ）是模拟生物界自然选择和变异机制的一种随机并行搜索优化算法。本文提出了应用于直接序列扩频通通信中窄带干扰抑制的基于进化规划的自适应非线性滤波技术，并与传统的自适应非线性滤波技术进行了比较，结果表明本文算法更优。不仅实现了自适应非线性滤波的全局寻优和快速收敛，而且提高了系统的稳定性，尤其对于极点靠近单位圆的ＡＲ模型信号干扰，滤波性能有较大的提高。     

基于自适应区域的光斑中心鲁棒性研究

激光光斑中心检测中,为了在保证光斑中心定位精度的前提下提高计算效率,采用改进的模板匹配算法, 进行了理论分析和实验验证。结果表明, 在未曝光的情况下,自适应感兴趣区域(ROI)平均计算时间为897s,而传统的模板匹配算法的平均计算时间为3388s;存在曝光的情况下,自适应ROI的平均计算时间为921s,传统模板匹配算法的平均计算时间为3389s。改进的自适应算法在激光光斑定位的实验测试方面表现优异,表明其可以在保证精度的前提下较好地提高计算效率。     

在不同移动速度下的无线链路自适应的实现分析

首先简单介绍了两种直接链路自适应技术AMC，H-ARQ，讨认弛不同的用户移动速度对信道估计的影响，说明用户移动速度差别很大时应采用不同的链路自适应技术；然后提出了一种在用户高速移动时的间接链路自适应技术并对其进行了分析，分析结果表明这种间接链路自适应技术在用户高速移动时的性能优于现在的通用的直接链路自适应技术。     

On the LTI properties of adaptive feedforward systems with tapdelay-line regressors

It is shown that an adaptive system whose regressor is formed by tap delay-line (TDL) filtering of a multitone sinusoidal signal is representable as a parallel connection of a linear time-invariant (LTI) block and a linear time-varying (LTV) block. A norm-bound (induced 2-norm) is computed explicitly on the LTV block and is shown to decrease as N^-1, where N is the number of taps. Hence, the adaptive system becomes LTI in the limit as the number of taps goes to infinity. In the more realistic case where the number of taps N is finite, the new “LTI plus norm-bounded perturbation” representation renders, for the first time, the adaptive system analyzable by standard robust control methods     

Adaptive vehicle skid control

In this paper, adaptive vehicle skid control, for stability and tracking of a vehicle during slippage of its wheels without braking, is addressed. Two adaptive control algorithms are developed: one for the case when no road condition information is available, and one for the case when certain information is known only about the instant type of road surface on which the vehicle is moving. The vehicle control system with an adaptive control law keeps the speed of the vehicle as desired by applying more power to the drive wheels where the additional driving force at the non-skidding wheel will compensate for the loss of the driving force at the skidding wheel, and also arranges the direction of the vehicle motion by changing the steering angle of the two front steering wheels. Stability analysis proves that the vehicle position and velocity errors are both bounded. With additional road surface information available, the adaptive control system guarantees that the vehicle position error and velocity error converge to zero asymptotically even if the road surface parameters are unknown.     

自适应极化滤波器的理论性能分析

为适应变化的电磁环境,自适应极化滤波器通常先采用极化估计器获得干扰场的极化状态,然后以最佳极化进行极化滤波.因此,自适应极化滤波器可用极化估计器、最佳极化计算器、极化滤波器这三者级联构成的开环模型来表示.在此模型基础上,针对基于正交极化双通道测量的信号极化矢量估计算法,研究了极化估计器的理论性能,证明了极化估计误差近似服从瑞利分布.通过研究极化估计误差在极化滤波器中的传播过程,导出了自适应极化滤波器理论性能的解析公式,清楚地揭示了滤波性能与信噪比等因素的统计关系.