Kind Of Compensation Method Research Articles

Noise Compensation Methods for Optical Fiber Frequency Sweeping Interferometry: A Review

Noise induced by the fluctuation of laser phase, frequency, intensity, etc., can deteriorate the point spread function (PSF) in distributed optical fiber sensing and testing systems, which is the core concern for measurement performance, such as measurement spatial resolution, length range, accuracy and dynamic range. In this paper, we review the development of noise compensation methods for improving the PSF in optical fiber frequency sweeping interferometry (OFFSI) systems and provide a reference to select appropriate compensation methods in different applications (e.g., fiber optics component characterization, optical fiber network diagnosis). A discussion of noise impacts on PSF is made, including laser source phase noise, laser source intensity noise and ambient noise. The most serious noise is the laser source phase noise involved in frequency tunable lasers, including deterministic frequency tuning nonlinearity and stochastic laser phase noise. Also, a comprehensive and detailed classification of the compensation strategies for different noise is provided according to the dominant noise in the laser source. Recent progress on each kind of compensation method is analyzed based on the principles, performance, advantages and limitations, and a comparison of compensation methods is presented. Finally, an overview of trends and future developments is given.

Capacitor-Less Low-Dropout (LDO) Regulator With 99.99% Current Efficiency Using Active Feedforward and Reverse Nested Miller Compensations

In this paper, an output capacitor-less low-dropout (LDO) regulator with 99.99% current efficiency using active feedforward compensation (AFFC) and reverse nested Miller compensation (RNMC) is implemented. To increase the current efficiency, low quiescent current less than 10 μA is used. The stability problem arising from the low bias current is overcome by applying two kinds of compensation methods. By drawing the pole-zero plot using the open-loop transfer function obtained by the small-signal modeling, the stability of the proposed LDO is guaranteed to be less than 70 mA. By using the proposed compensation methods, two zeros of the right-half plane (RHP) can be placed in the left-half plane (LHP) to prevent lagging and reduce the on-chip compensation capacitor. The current efficiency of the proposed LDO is 99.99% at the load current of 70 mA.

A rapid hybrid wave front correction algorithm for sensor-less adaptive optics in free space optical communication

Abstract In free-space optical communication (FSOC) system, wave front sensor-less adaptive optics (AO) technology is widely used to compensate wave front distortions caused by atmospheric turbulences. There are different kinds of compensation methods with both advantages and disadvantages. The conventional and often considered model-free algorithm, stochastic parallel gradient descent (SPGD) algorithm, requires a lot of iterations to obtain optimal solution, which may lead to a poor real-time performance. The newly developed model based algorithms have certain constraints and difficulties for the construction of the models. Therefore, in order to develop a rapid wave front distortion compensation algorithm with better performance, we present a hybrid method by a suitable combination of SPGD algorithm and a model-based algorithm presented by Martin J. Booth. Simulations under our built experiment platform show that this hybrid method can compensate wave front aberrations fitted by the Zernike polynomials in higher speed than that of SPGD algorithm at higher SR and lower RMS with strong turbulence, which means it can improve communication quality.

Did CEO’s Equity-Based Compensation Benefit Firms at All? – Evidence From the Regime Before Adoption of Statement of Financial Accounting Standards 123(R)

Previous studies documented empirical evidence that stock- and option-based compensation exacerbates the agency problem, which is opposite to the goal of awarding such kind of compensations to executives. If the stock- and option-based compensation is so bad, why did companies previously adopt such kind of compensation method. I use data from 1992-2005, a period before the adoption of FAS 123 (R), to examine whether the stock-based and option-based compensation benefits firms at all. I find that the firms, whose CEOs received higher values of stock- and option- compensations, have higher accruals quality and more predictable reported earnings, as well as enjoy lower implied costs of equity capital.These findings are robust to various sensitivity tests. The results indicate that such compensation method at least provided certain benefits to the firms.

Research on Reactive Power Compensation Optimization of 35kV Three Phase Unbalanced Distribution Network System

In view of the actual situation of three-phase load unbalance in distribution power system, a three-phase load balancing compensation method for three-phase-and-three-wire systems in distribution network is proposed, and load model is established. Then I have deduced the mathematical model of three-phase load compensation in distribution network, and analyzed the energy loss of the two kinds of compensation method about the power supply and the dispersion compensation on the load spot. It is verified that the load end compensation can contribute more to the reduction of energy loss, under the premise of ensuring active load, possess more economical, this method has important significance for the solution in research on reactive power compensation optimization of three phase unbalanced distribution power network.

Study of Symbol Detection Performance of Two Kinds of Compensation Method

Pulse coding/frequency modulation (PCM/FM) system is a rocket system mainly adopts remote sensing system, and MSD (Multi - Symbol Detection) is to overcome the traditional demodulation methods threshold effect. For multiple symbol detection misjudgment rate is higher in the process of problem, put forward two compensation methods: under the premise of without changing the length of the observation, every time by changing the length of sliding between the ruling and ultimately achieve the purpose of reduce misjudgment. The simulation analysis and test results verified the effectiveness and applicability of two kinds of compensation algorithm.

Undersampling Digital Predistortion Compensation Technology Based on Broadband Signals

Nonlinearity of power amplifier always results in spectrum spreading on input signal. When using digital predistortion technology to compensate power amplifier's nonlinearity, the required sampling frenquence for the output signal of amplifier is times of the original signal. The undersampling predistortion method can reduce the sampling frequency requirements. However, for the broadband signal, due to the significant memory effect of the power amplifier, the performance of undersampling digital predistortion is not satisfactory. In order to improve the undesirable predistortion performamce, this paper presents two kinds of undersampling digital predistortion compensation methods. For different sampling frequencies, the predistortion performances of these two kinds of compensation methods are different.

Magnetic Field Improved ULF-NMR Measurement in an Unshielded Laboratory Using a Low-Tc SQUID

Abstract Ultra Low Field Nuclear Magnetic Resonance (ULF-NMR) measurements were performed in an urban laboratory environment using a 2 nd order low- T C SQUID gradiometer. To improve the magnetic environment around the sample, two kinds of compensation methods were developed. Firstly, a spatially correlated active compensation system which includes two separated sets of squared Helmholtz coils, a 3-axis fluxgate and a home-made Proportional Integral Differential (PID) feedback electronics were developed to suppress the low frequency fluctuation. The low frequency disturbance of environmental magnetic field can be suppressed over two orders of amplitude. Secondly, linear gradient compensation in three directions was introduced to improve the homogeneity of the environmental magnetic field. Combining the two methods mentioned above, the relaxation time T 2* of proton was measured to be about 0.45s, and the signal-to-noise ratio of spectrum was improved by a factor of 9 for a 50 times averaged signal.

A Novel Method of Load Compensation Under Unbalanced and Distorted Voltages

In this paper, load compensation techniques under unbalanced and distorted voltages have been discussed. Two kinds of compensation methods are considered. In the first category, synchronous detection and modified equal current strategies are used under the unbalanced but sinusoidal source voltages. In the second method, load compensation based on instantaneous symmetrical component theory with positive sequence extraction is proposed and is shown to work under unbalanced and the non-sinusoidal source voltages. To support the proposed method, a 440 V (L-L) three-phase, four-wire distribution system is considered. The compensator is realized using a three-phase voltage source inverter (VSI) operated in the current control mode. Detailed digital simulation and experimental results are presented to validate the approach