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Wideband frequency electromagnetic (EM) noise generated during the turn-ON and turn-OFF processes of thyristor valves in converter stations is conducted along the primary circuitry, and may interfere with secondary systems. The EM interference (EMI) problem in a [+ or -]800 kV ultra-HVdc converter station is an important issue that should be studied carefully in the design stage. A method to analyze the conducted EM disturbance (EMD) based on time-domain wideband circuit simulation is proposed here, which is verified through the field test results of a [+ or -]500 kV converter station. Models of major equipment are described. The EMD levels of a [+ or -]800 kV converter station, which is currently being planned and built in China, are calculated, and compared with those of a [+ or -]500 kV converter station. Index Terms--Electromagnetic (EM) conductive interference, generation mechanism, HVdc substation, influence factors, ultra-HV (UHV) transmission.

This paper investigates potential improvement of nonparametric detection performance via addition of noise and evaluates the performance of noise modified nonparametric detectors. Detection performance comparisons are made between the original detectors and noise modified detectors. Conditions for improvability as well as the optimum additive noise distributions of the widely used sign detector, the Wilcoxon detector, and the dead-zone limiter detector are derived. Finally, a simple and fast learning algorithm to find the optimal noise distribution solely based on received data is presented. A near-optimal solution can be found quickly based on a relatively small dataset. Index Terms--Hypothesis testing, noise enhanced detection, nonparametric detection.

In high-density perpendicular magnetic recording channels, nonlinear transition shift (NLTS) is one of the distortions that can degrade the system performance. Write precompensation is a standard method used to combat the negative effect of NLTS. In this paper, we propose a modified pattern-dependent noise predictive (PDNP) detection algorithm for use on channels with electronics noise, transition jitter noise, and NLTS. We show that this detector can offer significant improvement in bit-error-rate (BER) compared to conventional Viterbi and PDNP detectors. Moreover, the system performance can be further improved by combining the new detector with a simple write precompensation scheme. Index Terms--Jitter noise, NLTS, pattern-dependent noise prediction, perpendicular recording.

Low-frequency noise was studied in MgO magnetic tunnel junctions (MTJs). The junctions were analyzed under saturating magnetic fields to minimize the noise of magnetic origin. Low-frequency noise of magnetically saturated MTJs is dominated by two different types of electrical noise: 1/f noise and random telegraph noise (RTN). 1/f noise is always present and represents the ultimate limitation for low-frequency applications. The RT noise component has a higher contribution for lower resistance area (RA) product samples and its magnitude increases with bias voltage. The 1/f noise of different MTJs can be compared using the Hooge parameter ([alpha]). This paper shows a systematic decrease in [alpha] with increasing bias voltage for MTJs with varying RA. All the MTJs studied, for both memory and sensor applications with single and double barrier, exhibit higher [alpha] variations while saturated in the anti-parallel state (AP) and no significative dependence on bias polarity was observed. Variations above one order of magnitude were observed for MTJs with RA > 10 k[ohm] x [micro][m.sup.2] in the AP. For the same bias voltage, the lowest [alpha]'s were always obtained in the parallel state (P). The lowest [alpha](~ 1 [E.sup.-10] [micro][m.sup.-2]) was obtained for the lower RA sample (~500 [ohm] x [micro][m.sup.2]) saturated in P, with an applied bias voltage of 600 mV. Index Terms--1/f noise, double barrier, low-frequency noise, magnetic tunnel junction, MgO, random telegraph noise.

We propose a new decoding algorithm based on a cascade structure for impulsive noise correction in multicarrier systems such as Orthogonal Frequency Division Multiplexing (OFDM) based systems. This new cascade structure based algorithm has the advantage to lead on one hand to a reduced-complexity implementation in an OFDM demodulator and on the other hand to overcome the lacks of other algorithms dedicated for impulsive noise correction. To do so, we start the derivation by investigating closed-form analytical expressions of the a priori probabilities used in hypotheses tests that are necessary for the different steps needed for the execution of the cascade structure based decoding algorithm. Such closed-form expressions for the a priori probabilities, result in efficient setups of the threshold values used for the execution of the decoding algorithm. Furthermore, we show that this cascade structure can be applied to efficiently cancel the impulsive noise in OFDM systems. As the clipping event, present in OFDM systems, can be seen as an additive impulsive noise, we prove that after introducing some minor modifications, we can apply the proposed cascade structure to significantly reduce the Peak to Average Power Ratio (PAPR) level in such systems. Simulation results are given to illustrate the usefulness of the proposed algorithm results in practical OFDM based communication systems such as Hiperlan 2. Index Terms--Impuisive noise, OFDM, PAPR, Hiperlan2, cascade structure.

A technique to predict the 1/f phase modulation (PM) and 1/f amplitude modulation (AM) noise due to up-conversion of 1/f baseband current noise in microwave heterojunction bipolar transistor (HBT) amplifiers is described. The method could be used to optimize amplifier design for low PM and AM noise in which amplifier PM noise could be reduced by 9 dB by adjusting the value of the input coupling capacitor.

A new approach is described and analyzed for signal expansion with respect to hybrid dictionaries that are based on probabilistic modeling. The results have shown the effectiveness of the approach for audio signals and among the different algorithms described, mean-field algorithms are the most efficient, in terms of expected results and computing time.

In thermal light ghost imaging, the transparent mask, located in the object arm of the optical setup, is numerically reconstructed by correlating the speckle patterns acquired by the video camera with the output of a bucket detector placed behind the mask. We show that the visibility of images can be significantly improved by discarding every speckle pattern whose bucket output falls below a certain threshold. We also demonstrate that the efficiency of the conventional method strongly decreases when the speckle statistics deviate from the negative exponential, whereas the threshold method is more robust against changes in the statistical distribution of the speckle intensity. We also provide reasonable statistical explanations for these results. OCIS codes: 100.0100, 030.4280.

The problem of maximum likelihood subspace learning and detection in the presence of Laplacian noise and interference whose subspace might be known or unknown is illustrated. The Laplacian version of the Gaussian-based t-statistic detector is found to be more sensitive while being also robust to false alarms and it has a computationally simple structure.

A mathematical framework is developed for analyzing the stochastic resonance (SR) effect in binary hypothesis testing problems and also a mechanism for SR noise enhanced signal detection. The SR phenomenon can be applied to many signal processing problems such as distributed detection and fusion as well as pattern recognition applications.

A Bayesian wavelet-based denoising procedure for multicomponent images which makes use of Gaussian scale mixtures as prior models that approximate the marginal distribution of the wavelet coefficients is presented.

Two methods for estimation of nonstationary noise based upon models of image structure which locally separate signal from noise that could be used to improve the stability of contrast change and nonstationary noise is demonstrated.

1/f-type of low frequency noise is widely observed in today's state-of-the-art tunneling-magneto-resistive (TMR) and current-perpendicular-to-plane (CPP), and giant-magneto-resistive (GMR) heads. In this paper, the 1/f-type magnetic noise arising from the thermally excited low frequency edge magnetization switch of the free layer is studied by micromagnetic simulation. It is found that although the free layer dimension is in the single domain regime, the edge magnetization random switching related to the thermal excitation and insufficient hard bias field on sensor edge can be a significant low frequency noise contributor in TMR/CPP GMR heads. A strong local hard bias (HB) field at sensor edge that pins the free layer edge magnetization is found to be more critical than a strong averaged HB field across the sensor to avoid magnetic 1/f-type noise. The simulation study shows that a high HB field gradient from sensor edge to center is preferred to maintain a low noise sensor while still achieving high sensitivity. This paper will also discuss the roles of free layer thickness, sensor geometry, current field, temperature, and air-bearing surface physical defect in the behavior of this edge flipping noise. Index Terms--1/f noise, current-perpendicular-to-plane (CPP), hard bias (HB), thermal excitation, tunneling-magneto-resistive (TMR).

The fuzzy filter, consisting of two different subfilters is designed to reduce the additive noise for the digital color images and has proved to be extremely advantageous, as it exhibits the denoising capability and reconstruction capability of the destroyed color component differences.

The shape-adaptive discrete cosine transform (SA-DCT) transform is found to be extremely useful for the denoising and deblocking of grayscale and color images, hence providing clean reconstructed edges without any unpleasant ringing artifacts due to the adaptive support provided by the structural constraints.

In the study of optical testing, the computed tomogaphy technique has been widely adopted to reconstruct three-dimensional distributions of physical parameters of various kinds of fluid fields, such as flame, plasma, etc. In most cases, projection data are often stained by noise due to environmental disturbance, instrumental inaccuracy, and other random interruptions. To improve the reconstruction performance in noisy cases, an algorithm that combines a self-adaptive prefiltering denoising approach (SPDA) with a multicriterion iterative reconstruction (MCIR) is proposed and studied. First, the level of noise is approximately estimated with a frequency domain statistical method. Then the cutoff frequency of a Butterworth low-pass filter was established based on the evaluated noise energy. After the SPDA processing, the MCIR algorithm was adopted for limited-view optical computed tomography reconstruction. Simulated reconstruction of two test phantoms and a flame emission spectral tomography experiment were employed to evaluate the performance of SPDA-MCIR in noisy cases. Comparison with some traditional methods and experiment results showed that the SPDA-MCIR combination had obvious improvement in the case of noisy data reconstructions. OCIS codes: 100.3010, 100.2000, 120.2440.

A novel adaptive network-based fuzzy inference system (ANFIS)-based filter (ABF) is described for the restoration of images corrupted by impulsive noise (IN). The results have indicated that the proposed filter achieves a better performance than the comparison filters in terms of noise suppression and detail preservation, even when the images are highly corrupted by IN.

In this paper, we treat nonlinear active noise control (NANC) with a linear secondary path (LSP) and with a nonlinear secondary path (NSP) in a unified structure by introducing a new virtual secondary path filter concept and using a general function expansion nonlinear filter. We discover that using the filtered-error structure results in greatly reducing the computational complexity of NANC. As a result, we extend the available filtered-error-based algorithms to solve NANC/LSP problems and, furthermore, develop our adjoint filtered-error-based algorithms for NANC/NSP. This family of algorithms is computationally efficient and possesses a simple structure. We also find that the computational complexity of NANC/NSP can be reduced even more using block-oriented nonlinear models, such as the Wiener, Hammerstein, or linear-nonlinear-linear (LNL) models for the NSP. Finally, we use the statistical properties of the virtual secondary path and the robustness of our proposed methods to further reduce the computational complexity and simplify the implementation structure of NANC/NSP when the NSP satisfies certain conditions. Computational complexity and simulation results are given to confirm the efficiency and effectiveness of all of our proposed methods. Index Terms--Active noise control (ANC), adaptive filters, nonlinear filters, nonlinear systems.

An analysis of the quantization noise introduced by a widely-used class of single-quantizer digital delta-sigma ([DELTA] [SIGMA]) modulators with low-level, 1-bit dither is presented. Necessary and sufficient conditions are derived that ensure, in an asymptotic sense, various ensemble statistical properties of the quantization noise such as uniformity and independence from the input and delayed versions of itself. The conditions are also shown to be sufficient for a single realization of the quantization noise sequence to possess these properties in a time-averaged sense. Several of the most commonly-used digital [DELTA] [SIGMA] modulators are shown to satisfy the conditions. Index Terms--Delta-sigma ([DETLA] [SIGMA]) modulation, dither techniques, quantization.

The implementation of OFDM system suffers from the effect of phase noise (PHN) generated by local oscillator (LO), which disturbs the orthogonality among subcarriers and causes intercarrier interference (ICI). In frequency domain, the received signal can be formulated as the circular convolution of the transmitted signal and the ICI weighting function. In this paper, the symmetric conjugate property of the ICI weighting function is investigated. Based on that, the ICI self-cancellation of symmetric data-conjugate method is studied to suppress PHN. A new ICI cancelling demodulation (ICD) scheme with frequency diversity combining is proposed. Under flat fading channel, the carrier-to-interference ratio (CIR) improvement from this proposed method is larger than 22 dB, and can tolerate a phase noise with standard deviation of 7 deg when BER is [10.sup.-3]. In frequency selective fading channel, the proposed method is shown to be able to offer significant diversity gain. Index Terms--frequency diversity, intercarrier interference (ICI), orthogonal frequency division multiplexing (OFDM), Phase noise (PHN).

In this paper, we report a method for nonuniform data-dependent noise prediction (DDNP), in which the noise predictive filters do not have an identical order (number of taps). To accommodate this new architecture, we implemented a partial decision feedback strategy for branch metric computations of the higher order predictive filters. Theoretical analysis and computer simulations show that our proposed DDNP can achieve a better tradeoff between detection performance and computational complexity compared with the previously reported DDNP. Index Terms--Bit-error rate, data-dependent noise prediction, pairwise error event probability, partial decision feedback, perpendicular recording.

Various experiments and studies are conducted to fabricate and systematically characterize the low frequency (f) noise properties of the ZnO nanowire field effect transistors (FETs), which are commonly used in several complementary-metal-oxide-semiconductor (CMOS) electronic applications. The analysis reveals that the presence of an oxygen environment increases the fluctuations on the nanowire surfaces, which makes it useful for numerous other applications.

The experiments demonstrate that the p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated on silicon-on-insulator (SOI) substrates exhibit a lower magnitude of the 1/f noise, which is studied as a function of the back gate voltage. The results show that the 1/f noise is highly affected by the channel positioning of silicon and increases with an increase in the back gate voltage that push the carriers towards the front gate oxide interface.

The measurement, analytical analysis and Monte Carlo simulation of the frequency and bandwidth dependence of MOSFET low-frequency (LF) noise behavior are presented. The analytical formulation is validated through comparison of numerical simulation and experimental results, including the analysis of frequency dependence.

This brief describes a design technique for multistage preamplifiers of the type commonly used in high-performance comparators. Following the examination of multistage preamplifier responses in both the spectral and time domains, and a consideration 1/f noise attenuation in topologies employing offset storage capacitors, a procedure for optimizing both the number of stages and the offset storage capacitance is presented. As a demonstration vehicle, a comparator with a 13-Msample/s conversion rate and 200-[micro]V minimum input resolution is designed for realization in a 0.4-[micro]m CMOS technology under the constraint of a power dissipation of 250 [micro]W when operating from a 2.5-V supply. In this design, the effective input signal is 33 [micro]V for the minimum input resolution of 200 [micro]V due to signal corruption from circuit noise and residual error from incomplete settling. Index Terms--Analog-digital conversion, circuit noise, circuit optimization, CMOS analog integrated circuits, comparators.

The iterative regularization method and the inverse scale space method, which is developed for total-variation (TV) based image restoration, are generalized for the wavelet-based image restoration. The results have shown that the iterative procedure applied to soft shrinkage has given firm shrinkage and has converged to hard shrinkage.

A spatial denoising method is proposed that is based on an averaging process performed on a set of Markhov Chain Monte-Carlo simulations of region partition maps constrained to be spatially piecewise uniform for each estimated constant-value regions. The results have shown that the method performs competitively and better than the best existing wavelet-based denoising methods in benchmark tests.

A new coding scheme called robust coding, which uses an arbitrary number of coding units to minimize the reconstruction error, can introduce redundancy in the code in order to compensate for channel noise. The numerical solutions of robust coding for high-dimensional image data has shown that the codes are more robust than other linear image coding methods such as principal and independent component analysis (PCA or ICA), and wavelets.

A process for the complete experimental evaluation of the main working parameters for semiconductor lasers applicable to several types of market-available semiconductor lasers is described. The main advantage of the method is that it requires the use of only one setup for all the measurements, thereby making it much faster and easier to automate and could be applied to other types of single-mode semiconductor lasers without further revisions.

A triple-modulus phase-switching prescaler for high-speed operations is presented in this paper. By reversing the switching orders between the eight 45[degrees]-spaced signals generated by the 8:1 frequency divider, the maximum operating frequency of the prescaler is effectively enhanced. With the triple-modulus switching scheme, a wide frequency covering range is achieved. The proposed prescaler is implemented in a 0.18-[micro]m CMOS process, demonstrating a maximum operating frequency of 16 GHz without additional peaking inductors for a compact chip size. Based on the high-speed prescaler, a fully integrated integer-N frequency synthesizer is realized. The synthesizer operates at an output frequency from 13.9 to 15.6 GHz, making it very attractive for wideband applications in K u-band. At an output frequency of 14.4 GHz, the measured sideband power and phase noise at 1-MHz offset are -60 dBc and -103.8 dBc/Hz, respectively. The fabricated circuit occupies a chip area of 1 [mm.sup.2] and consumes a dc power of 70 mW from a 1.8-V supply voltage. Index Terms--Frequency synthesizers, high-speed operations, phase-locked loops (PLLs), phase-switching prescalers, programmable dividers, triple-modulus frequency division.

This paper presents a detailed analysis of the stressing mechanisms for highly rugged low-noise GaN monolithic-microwave integrated-circuit amplifiers operated at extremely high input powers. As an example, a low-noise amplifier (LNA) operating in the 3-7-GHz frequency band is used. A noise figure (NF) below 2.3 dB is measured from 3.5 to 7 GHz with NF < 1.8 dB between 5-7 GHz. This device survived 33 dBm of available RF input power for 16 h without any change in low-noise performance. The stress mechanisms at high input powers are identified by systematic measurements of an LNA and a single high electronmobility transistor in the frequency and time domains. It is shown that the gate dc current, which occurs due to self-biasing, is the most critical factor regarding survivability. A series resistance in the gate dc feed can reduce this gate current by feedback, and may be used to improve LNA ruggedness. Index Terms--Amplifier noise, integrated-circuit noise, microwave field-effect transistor (FET) amplifiers, monolithic-microwave integrated-circuit (MMIC) amplifiers, noise, semiconductor device noise.

A functional link network with higher order statistics is introduced for signal enhancement, which uses the mean-square error (MSE) between higher order statistics of desired signals and filtered output. The results have shown that the performance of functional link network with higher order statistics is less sensitive to the selection of learning rates than the conventional functional link network and adaptive line enhancement. It is demonstrated that it can enhance signal more effectively under different noise levels for stationary and nonstationary Gaussian noises.

A statistical reconstruction framework is considered to characterize the strategies that are mean-squared error (MSE) admissible, meaning that they are not dominated in terms of MSE by any other linear reconstruction. Several classical estimation approaches are adapted to the particular sampling problem, which have suggested concrete admissible reconstruction methods.

A parametric suboptimal detection of a known deterministic signal embedded in [alpha]-stable noise is reported. The performance of the suboptimal receiver is compared with the performance of the optimal receiver and with the performance of several classical suboptimal receivers in the [alpha]-stable context.