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“信号与系统”是包括电气工程、电子信息工程、通信工程和自动化等本科专业重要的专业基础课程之一。本教材对应于全国双语示范课程。作者结合多年在国内外的教学经验及心得,针对当前双语教学及全英文教学现状,着眼于学生自学能力的培养和分析问题能力的提高,编写了本书。
本教材教辅资源完整,可到清华大学出版社网站本书页面下载。
侧重培养学生分析问题的能力及注重研究问题方法的学习。与现有同类中英文教材相比:
文字精炼,内容安排上采用模拟-离散双域交替的方式。
在处理常系数线性微分(差分)方程及由其描述的线性时不变系统及与变换的关系上有独到之处。
知识体系完整,系统及逻辑性强,同时也适用于自学。
内容简介
“信号与系统”是电气工程、电子信息工程、通信工程和自动化等本科专业重要的基础课程之一。《信号与系统基础/高等学校电子信息类专业系列教材》对应于“信号与系统”全国双语示范课程。书中凝练了作者多年的教学经验及心得,针对国内双语及全英文教学现状,力求培养学生的自学能力和分析问题的能力。
《信号与系统基础/高等学校电子信息类专业系列教材》特色:
1)文字简练,内容安排上采用模拟-离散双域交替的方式。
2)在处理常系数线性微分(差分)方程及由其描述的线性时不变系统与变换的关系上有独到之处。
3)知识体系完整,系统及逻辑性强,同时也适用于自学。详见书中前言(Preface)部分。
作者简介
李刚,教授,博士生导师,浙江省“钱江学者”特聘教授。1982年1月毕业于北京工业学院(现北京理工大学),1990年11月获比利时新鲁汶大学工学博士。1992年4月至2007年2月在新加坡南洋理工大学任教。长期从事数字信号处理、系统与控制理论等方面的教学与研究。主要研究方向为信号变换与压缩、数字系统结构与参数化理论及优化方法。
常丽萍,博士,副教授,2008年6月毕业于中国科学院上海光学精密机械研究所,目前在浙江工业大学信息工程学院从事教学和科研工作。研究方向为信号稀疏表示模型、压缩感知与信号检测等。
李胜,博士,讲师,2010年12月取得英国约克大学博士学位,曾获约克大学授予的K.M.Stott科研奖,于2011年10月在德国伊尔梅瑙工业大学通信研究实验室结束博士后工作。目前在浙江工业大学任教。主要研究方向包括自适应算法、无线通信系统、通信接收机设计、干扰消除等。
内页插图
目录
Preface
Chapter 1 Introduction
1.1 Overview of signals and systems
1.1.1 What is a signal?
1.1.2 What is a system?
1.2 Description and classification of signals
1.2.1 Continuous-time signals and discrete-time signals
1.2.2 Energy signals and power signals
1.2.3 Periodic signals and non-periodic signals
1.2.4 Deterministic signals and random signals
1.2.5 Elementary signals
1.3 Description of Systems
1.3.1 Elementary systems
1.3.2 System modelling
1.4 Properties of systems
1.4.1 Memoryless and with memory
1.4.2 Causality
1.4.3 Invertibility
1.4.4 Stability
1.4.5 Time-invariance
1.4.6 Linearity
1.5 Summary
1.6 Problems
Chapter 2 Time-domain Analysis of LTI Systems
2.1 Introduction
2.2 The unit impulse response and convolutions
2.2.1 The convolution sum ~
2.2.2 The convolution integral
2.3 Properties of convolutions and equivalent systems
2.4 Causality and stability of LTI systems
2.5 Systems constrained with LCCDEs
2.5.1 Continuous-time systems constrained with LCCDEs
2.5.2 Discrete-time systems characterized by LCCDEs
2.6 Summary
2.7 Problems
Chapter 3 Fourier Analysis of Signals
3.1 Introduction
3.2 Fourier series for continuous-time periodic signals
3.3 Fourier series for discrete-time periodic signals
3.4 Why should a signal be transformed?
3.5 Fourier transform for continuous-time signals
3.5.1 Properties of Fourier transform
3.5.2 Inverse Fourier transform
3.6 The discrete-time Fourier transform
3.6.1 Properties of DTFT
3.6.2 Inverse DTFT
3.7 Fourier series and Fourier transforms
3.8 Summary
3.9 Problems
Chapter 4 Frequency-domain Approach to LTI Systems
4.1 Introduction
4.2 Frequency response of LTI systems
4.3 Bode plots for continuous-time LTI systems
4.4 Frequency response of LTIs described with LCCDEs
4.5 Frequency domain approach to system outputs
4.6 Some typical LTI systems
4.6.1 All-pass systems
4.6.2 Linear phase response systems
4.6.3 Ideal filters
4.6.4 Ideal transmission channels
4.7 Summary
4.8 Problems
Chapter 5 Discrete Processing of Analog Signals
5.1 Introduction
5.2 Sampling of a continuous-time signal
5.3 Spectral relationship and sampling theorem
5.4 Reconstruction of continuous-time signals
5.5 Hybrid systems for discrete processing
5.6 Discrete Fourier transform
5.7 Compressed sensing
5.8 Summary
5.9 Problems
Chapter 6 Transform-domain Approaches
Chapter 7 Structures and State-space Realizations
Chapter 8 Comprehensive Problems
Appendices
Bibliography
前言/序言
The concepts of signals and systems are the corner-stone of a wide variety of areas, ranging from home-oriented consumer electronics and multimedia entertainment products to sophisticated communications, aeronautics and astronautics, and control. The ideas and approaches associated with these concepts have great e.ects on our life in one way or another. Although the signals and systems which arise across those .elds are naturally di.erent in their physical make-up and application, the principles and tools for analyzing signals and systems are the same and hence applicable to all of them. Therefore, an introductory course on signals and systems is fundamental and compulsory for an engineering under-graduate curriculum in any well-established tertiary (education) institutions. Such a course is commonly designed in one of the two forms below:
.
a one-semester subject that intends to provide students with a rich set of concepts and tools for analyzing deterministic signals and an important class of systems known as linear time-invariant systems;
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a two-semester subject that expands on the one-semester course by adding more detailed treatment of signal processing and systems for speci.ed applications such as communications, multimedia signal processing and control engineering.
This book takes the .rst form and assumes that the students have a background in calculus and introductory physics.
Why another “Signals and Systems”?
Given that there are many well-written textbooks on signals and systems available, our readers would be screaming when seeing this textbook: Why another “Signals and Systems”?
The thought of writing such a textbook was stimulated in 2007 when the .rst author conducted a 2nd year course on signals and systems in Zhejiang University of Technology (ZJUT) in Hangzhou, which he just joined from Nanyang Technological University (NTU), Republic of Singapore. The course was designed as “shuang yu ke” spelled in Chinese, meaning that the teaching materials such as the textbooks and slides are all in English and as to the class language, the lecturers can choose either Chinese, English or a mixture of the two—a typical Chinese style! The textbooks adopted were those popularly used in the world but were found very di.cult to most of our students as their English is not good enough to deal with those textbooks of one thousand pages or so in length.1 This motivates him to write a new “Signals and Systems”
1Here, we have those big masters of Signals and Systems to “blame”—why not writing their text-book in Chinese!
with a primary objective of providing a condensed version of “Signals and Systems” in English, while keeping the important technical materials as much as possible.
Most of us agree that for a university study it is more important to teach students how to learn and analyze than what to be learned and analyzed. The .rst author still remembers what was said by Professor Y. Liu who taught him calculus in 1978 in Beijing Institute of Technology (BIT) (now, known as Bei Li Gong) that a good textbook, say of ten chapters, should be written in such a way that after the .rst four chapters taught by the lecturer, the rest can be studied by students themselves easily. What Prof. Liu really meant is that a textbook should be written to facilitate and reinforce self-study. This is another objective that this textbook is intended to achieve. Given the mathematical nature of this subject, rigidity should be sustained as much as possible, which is something very important to engineering students to learn. This is the third objective of this textbook.
How the book is structured ?
One of the reasons for the existing textbooks of signals and systems to have easily over eight hundred pages is due to the continuous-and discrete-time forms of signals and systems. The success of a signals and systems that achieves our primary object lies in how to provide a balanced and integrated treatment of the two forms in a pedagogical way that can help students see the fundamental similarities and di.erences between the two without too much repeating. With all of these in mind, this book is organized as follow.
. Chapter 1 is aimed to provide an overview of signals and systems. Compared with the one in most of the signals and systems, it is condensed with an emphasis on the periodical signals and linear time-invariant (LTI) systems.
. Chapter 2 deals with the time-domain approach to the LTI systems. Since the key to the development of this chapter is to exploit the properties of linearity and time-invariance as well as signal decompositions, the concepts of unit impulse re-sponse and convolution are developed in details for the discrete-time case, while the continuous-time counterparts are directly given. One of the remarkable points emphasized in this chapter is the equivalence between the LTI systems and con-volutions, which relates the physical interpretation and mathematical expression. Another important technical point in this chapter is the establishment of a con-clusion which states that any complete solution of a linear constant coe.cient di.erential/di.erence equation (LCCDE) can be characterized by the sum of the output of an LTI system excited by the force signal and a homogeneous solution of the LCCDE. This conclusion yields a very clear picture of the relationship be-tween an LCCDE and the systems that it can characterize. With the help of the
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《现代通信原理与技术》 内容简介 本书旨在系统深入地阐述现代通信系统的基本原理、核心技术及其发展趋势,面向高等院校电子信息类、通信工程等专业的学生及相关领域的科研人员和工程技术人员。本书以清晰的逻辑结构、严谨的学术语言,结合丰富的工程实例,力求为读者构建一个全面而深入的通信知识体系。 第一部分:通信系统基础 本部分将从最基础的概念入手,为后续深入的学习奠定坚实的理论基础。 第一章 信号的分类与基本性质: 深入探讨了信号在通信系统中的重要性,详细介绍了信号的各种分类方法,包括模拟信号与数字信号、周期信号与非周期信号、能量信号与功率信号、确定信号与随机信号等。同时,详细分析了信号的幅度、频率、相位、带宽、频谱等基本性质,并通过大量实例展示了这些性质在信号分析中的应用。例如,讲解了如何通过傅里叶级数和傅里叶变换分析周期信号和非周期信号的频谱特性,从而理解信号的频域表示及其在系统设计中的意义。 第二章 线性时不变系统(LTI)的分析: 聚焦于通信系统中最基本也是最重要的模型——线性时不变系统。详细阐述了LTI系统的定义、基本性质(如叠加性、时移不变性)及其重要性。着重介绍了LTI系统的系统函数(传递函数)的概念,以及如何利用它来描述系统的动态特性。本书将深入讲解卷积运算在LTI系统分析中的核心作用,详细推导并解释卷积积分和卷积和的计算方法,并展示如何通过卷积来预测系统对任意输入信号的响应。此外,还会引入LTI系统的频率响应,分析其与系统函数的关系,以及频率响应如何在信号的传输和处理过程中影响信号的频谱。 第三章 傅里叶变换及其在信号分析中的应用: 傅里叶变换是分析和处理信号不可或缺的工具。本章将系统地介绍傅里叶级数和傅里叶变换的数学理论,包括连续时间傅里叶变换(CTFT)、离散时间傅里叶变换(DTFT)和离散傅里叶变换(DFT)。深入讲解了傅里叶变换的基本性质,如线性性、时移性、频移性、对称性、卷积定理等,并详细阐述了这些性质在信号分析和系统分析中的具体应用。通过丰富的例子,展示如何利用傅里叶变换分析信号的频谱特性,理解信号的带宽限制,以及如何通过频谱分析来设计滤波器、进行信号解调等。 第四章 拉普拉斯变换与Z变换: 介绍了复指数信号的表示及其在系统分析中的优势。拉普拉斯变换是分析连续时间LTI系统的有力工具,本章将详细介绍拉普拉斯变换的定义、性质、收敛域,以及如何利用它来求解LTI系统的零输入响应和零状态响应。Z变换则是分析离散时间LTI系统的关键,本书将系统介绍Z变换的定义、性质、收敛域,并讲解如何利用Z变换来求解离散LTI系统的差分方程,分析系统的稳定性以及传递函数。拉普拉斯变换和Z变换的应用实例将贯穿本章,帮助读者理解它们在电路分析、系统稳定性判断和滤波器设计等方面的作用。 第二部分:信息传输与调制技术 本部分将重点探讨如何将信息有效地加载到载波上进行传输,以及相关的调制与解调技术。 第五章 模拟调制技术: 深入探讨了幅度调制(AM)、频率调制(FM)和相位调制(PM)等经典的模拟调制技术。详细讲解了各种调制方式的基本原理、产生方法和解调方法,并分析了它们各自的优缺点,如带宽占用、抗噪声能力、系统复杂度等。通过对AM、FM、PM信号的时域波形和频域频谱的详细分析,帮助读者理解调制过程对信号频谱的影响。同时,还将介绍一些特殊的模拟调制技术,如单边带(SSB)和双边带(DSB)调制,以及它们的应用场景。 第六章 数字调制技术: 随着数字通信的飞速发展,数字调制技术成为现代通信的核心。本章将系统介绍移幅键控(ASK)、移频键控(FSK)、相移键控(PSK)以及正交幅度调制(QAM)等主流数字调制技术。详细阐述了每种调制方式的原理、星座图、功率谱密度,并分析了它们在误码率、频谱效率和实现复杂度等方面的性能。本书还将讨论多进制调制技术,如M进制ASK、M进制FSK、M进制PSK等,以及它们如何进一步提高频谱利用率。 第七章 脉冲编码调制(PCM)与量化: 聚焦于将模拟信号转换为数字信号的关键过程。详细阐述了采样定理,讲解了理想采样、理想保持和实际采样之间的区别与联系。深入分析了量化过程,包括均匀量化和非均匀量化,并详细介绍了量化误差的产生及其对信号质量的影响。本书将重点介绍PCM编码的基本流程,包括采样、量化和编码,并分析其在语音、音频等领域的广泛应用。 第八章 匹配滤波器与最佳接收: 匹配滤波器是实现最佳接收、最大化信噪比的关键。本章将深入推导匹配滤波器的原理,阐述其如何最大化输出信噪比,并讲解匹配滤波器的结构和实现方法。同时,将介绍最佳接收机的概念,以及在 AWGN(加性高斯白噪声)信道下,采用匹配滤波器进行数字信号的判决过程。本书还将讨论非匹配滤波器及其在特定应用中的作用。 第三部分:通信系统中的噪声与干扰 噪声和干扰是影响通信系统性能的关键因素,本部分将深入分析这些因素并探讨抑制方法。 第九章 随机过程与噪声: 随机过程是描述噪声和随机信号的数学工具。本章将介绍随机过程的基本概念,如自相关函数、互相关函数、功率谱密度等,并重点介绍常见的随机过程模型,如平稳随机过程、马尔可夫过程和高斯过程。深入分析了热噪声、散粒噪声、闪烁噪声等各种噪声的产生机理及其统计特性。本书还将详细阐述高斯白噪声(AWGN)模型,并分析其在通信系统分析中的重要性。 第十章 噪声对模拟和数字通信系统的影响: 详细分析了噪声对模拟调制系统(AM、FM)和数字调制系统(ASK、FSK、PSK、QAM)的性能影响。通过对不同调制方式在噪声信道下的误码率(BER)和信噪比(SNR)进行数学推导和仿真分析,帮助读者直观理解噪声对通信质量的恶化作用。本书还将介绍一些衡量通信系统抗噪声能力的指标,并讨论提高系统抗噪声能力的方法,如增加发送功率、使用更鲁棒的调制方式等。 第十一章 干扰及其抑制: 除了噪声,其他信号或杂波也可能对通信系统造成干扰。本章将分类介绍各种常见的干扰类型,如同频干扰、邻频干扰、互调干扰、冲激噪声等。深入分析这些干扰的来源、传播途径及其对通信系统的影响。本书将重点探讨各种抑制干扰的技术,包括滤波器设计、扩频技术、编码技术等,并分析不同抑制方法的优缺点和适用场景。 第四部分:现代通信系统关键技术 本部分将聚焦于现代通信系统中不可或缺的关键技术,以及它们如何推动通信系统的进步。 第十二章 编码与纠错技术: 编码是提高通信系统可靠性的重要手段。本章将系统介绍信源编码(如霍夫曼编码、算术编码)和信道编码(如汉明码、卷积码、BCH码、LDPC码、Turbo码)的基本原理和编码方法。深入讲解了纠错码的原理,包括监督码、纠错码的编码和译码过程,以及它们如何在接收端检测和纠正传输过程中产生的错误。本书将分析不同编码方案的性能,以及它们在提高通信可靠性方面的作用。 第十三章 多路复用技术: 多路复用技术是提高通信线路利用率的关键。本章将详细介绍时分复用(TDM)、频分复用(FDM)和码分复用(CDM)等经典多路复用技术。深入分析各种复用技术的原理、实现方式和应用场景。本书还将介绍正交频分复用(OFDM)技术,并阐述其在高数据速率传输中的优势,以及在Wi-Fi、4G/5G等现代通信系统中的广泛应用。 第十四章 展频通信: 展频通信是一种抗干扰、抗侦测能力强的通信技术。本章将详细介绍直接序列扩频(DSSS)和跳频扩频(FHSS)等展频技术的基本原理。深入分析展频信号的产生和接收过程,并阐述展频通信在安全性、抗干扰性等方面的优势。本书还将探讨展频通信在军事通信、GPS等领域的应用。 第十五章 现代通信系统概览: 本章将对本书所学的知识进行总结和升华,并对现代通信系统进行概览。将介绍卫星通信、光纤通信、移动通信(包括4G、5G技术)、无线局域网(WLAN)等现代通信系统的基本架构、关键技术和发展趋势。通过对这些系统的分析,帮助读者将理论知识与实际工程应用联系起来,理解通信技术是如何不断发展的。 本书的特色 体系完整,逻辑清晰: 本书从信号与系统的基础概念出发,逐步深入到现代通信系统的核心技术,结构严谨,逻辑清晰,适合作为教材或参考书。 理论深入,联系实际: 强调理论与实际工程应用的结合,通过大量的工程实例和案例分析,帮助读者更好地理解抽象的理论概念,并掌握实际应用中的关键技术。 图文并茂,易于理解: 大量使用图表、波形和示意图,直观地展示信号、系统和通信过程,使复杂的概念更易于理解。 面向未来,突出前沿: 关注现代通信技术的发展趋势,例如OFDM、LDPC、Turbo码等,为读者提供前瞻性的知识。 通过学习本书,读者将能够深入理解通信系统的基本原理,掌握分析和设计通信系统的关键技术,为未来在通信领域的研究和工程实践打下坚实的基础。