### 数学代写|傅里叶分析代写Fourier analysis代考|MECH4424

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• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 数学代写|傅里叶分析代写Fourier analysis代考|Exponential Signal

By using sine and cosine functions, signals can be represented. But it involves two basic functions and the two associated constants. It is found that an equivalent representation of signals is obtained using the complex exponential function, in which only one basic function and one associated constant is involved. The compact representation and the ease of manipulating the exponential functions make its use mandatory in the analysis of signals and systems. However, practical devices generate sine and cosine functions. Euler’s formula is the bridge between the theory and the practice. With $b$ any positive real number except 1 ,
$$x(t)=b^{t}$$
is called the exponential function with base $b$. Our primary interest, in this book, is the complex exponential function of the form
$$x(\theta)=A e^{j \theta}$$
The base is $e$, which is approximately $2.71828$. The exponent is a complex number with its real part zero (pure imaginary number). The coefficient of the exponential $A$ is a complex number.

The exponential $e^{j \theta}$, shown in Fig. 1.5, is a unit rotating vector, rotating in the counterclockwise direction. The exponential carries the same information about a sinusoid in an equivalent form, which is advantageous in the analysis of signals and systems. In combination with the exponential $e^{-j \theta}$. which rotates in the clockwise direction, a real sinusoidal waveform can be obtained. Since
$$e^{j \theta}=\cos (\theta)+j \sin (\theta) \text { and } e^{-j \theta}=\cos (\theta)-j \sin (\theta),$$
solving for $\cos (\theta)$ and $\sin (\theta)$ results in
$$\cos (\theta)=\frac{e^{j \theta}+e^{-j \theta}}{2} \text { and } \sin (\theta)=\frac{e^{j \theta}-e^{-j \theta}}{j 2}$$

## 数学代写|傅里叶分析代写Fourier analysis代考|Periodic and Aperiodic Signals

The sinusoidal signals are defined by the values of the coordinates on a circle in Fig. 1.3. In each rotation of a point on the circle, the same set of values are produced indefinitely. This type of signals, such as the sine and cosine functions, is periodic signals. While only one period of a periodic signal contains new information, periodicity is required to represent signals such as power and communication signals. In communication engineering, the message signal is aperiodic and the carrier signal is periodic. Finite duration signals are represented, by the practically most often used version of the Fourier analysis, assuming periodic extension. The finite signal is considered as the values of one period and concatenation of it indefinitely on either side yields a periodic signal. A signal $x(t)$ is said to be periodic, if $x(t)=x(t+T)$, for all values of $t$ from $-\infty$ to $\infty$ and $T>0$ is a positive constant. The minimum value of $T$ that satisfies the constraint is the period. A periodic signal shifted by an integral number of its period remains unchanged. A signal that is not periodic is aperiodic, tial. The period is infinity, so that there is no indefinite repetition. The everlasting definition of a periodic signal is for mathematical convenience. In practice, physical devices are switched on at some time and the response reaches a steady state, after the transient response dies down.

## 数学代写|傅里叶分析代写Fourier analysis代考|Exponential Signal

$$x(t)=b^{t}$$

$$x(\theta)=A e^{j \theta}$$

$$e^{j \theta}=\cos (\theta)+j \sin (\theta) \text { and } e^{-j \theta}=\cos (\theta)-j \sin (\theta),$$

$$\cos (\theta)=\frac{e^{j \theta}+e^{-j \theta}}{2} \text { and } \sin (\theta)=\frac{e^{j \theta}-e^{-j \theta}}{j 2}$$

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。