CHAPTER 1 Signals and Signal Processing Wang Weilian wlwang@ynu.edu.cn School of Information Science and Technology Yunnan University

Outline Characterization and Classification of Signals Typical Signal Processing Operations Examples of Typical Signals Typical Signal Processing Applications Why Digital Signal Processing 云南大学滇池学院课程：数字信号处理

Characterization and Classification of Signals In mathematics: a function of independent variables In physics: anything that carries information Examples: speech, music, picture, and video signals Signal processing: To extract useful information carried by the signal In domain or in the transformed domain 云南大学滇池学院课程：数字信号处理

Characterization and Classification of Signals Signal classification 1-D / M-D signal Scalar — vector Real-valued — complex- valued Continuous-time / discrete-time signals Analog signal — digital signal A sampled-data signal — a quantized boxcar signal Deterministic / random signals 云南大学滇池学院课程：数字信号处理

Typical Signal Processing Operations Elementary Time-Domain Operations Scaling: Integration: Differentiation: Delay operation: Addition: Product of two signals: 云南大学滇池学院课程：数字信号处理

Typical Signal Processing Operations Filtering — convolutional integral To improve the quality of the signal To pass / block certain frequency components in a signal through the filter without any distortion Categories Lowpass filter Highpass filter Bandpass filter Bandstop filter notch filter Multiband filter comb filter 云南大学滇池学院课程：数字信号处理

Typical Signal Processing Operations Generation of Complex Signals A complex signal can be generated from a real signal by employing a Hilbert transformer Method: A real analog signal x(t) is passed through a Hilbert transformer The continuous-time Fourier transform of is The complex signal is 云南大学滇池学院课程：数字信号处理

Typical Signal Processing Operations Modulation Demodulation 低通滤波器 云南大学滇池学院课程：数字信号处理

Typical Signal Processing Operations Multiplexing and De-multiplexing For an efficient utilization of a wideband transmission channel Quadrature Amplitude Modulation Signal Generation Square waves Triangular waves White noise 云南大学滇池学院课程：数字信号处理

Examples of Typical Signals Electrocardiography ( ECG ) Signal Electroencephalogram ( EEG ) Signal Seismic Signals Diesel Engine Signal Speech Signals Musical Sound Signal Time Series Images 云南大学滇池学院课程：数字信号处理

Examples of Typical Signals Images Original Image Complement Image 云南大学滇池学院课程：数字信号处理

Typical Signal Processing Applications Sound Recording Applications Compressors and limiters Expanders and noise gates Equalizers and filters Noise reduction system Delay and reverberation systems Special effects Telephone Dialing Applications Dual-tone multi-frequency ( DTMF ) FM Stereo Applications Electronic Music Synthesis Echo Cancellation in Telephone Networks 云南大学滇池学院课程：数字信号处理

Why Digital Signal Processing DSP everywhere 云南大学滇池学院课程：数字信号处理

Why Digital Signal Processing Advantages: Less sensitive to tolerances of component value Enable to full integration Any desirable accuracy Timesharing Easy adjustment of processor characteristics during processing The impossible with analog implementation — linear phase, multi-rate processing … Cascade without any loading problems Stored almost indefinitely without loss of information 云南大学滇池学院课程：数字信号处理

Why Digital Signal Processing Disadvantages: The increased system complexity The limited range of frequencies available for processing Consume electrical power 云南大学滇池学院课程：数字信号处理

Summary This chapter provides an overview of signals and signal processing methods. The mathematical characterization of the signal is discussed along with a classification of signals. A review of some commonly used signal processing operations is provided and illustrated through examples. Advantages and disadvantages of digital processing of signals are discussed. We hope that you can feel interesting and indulge in DSP. 云南大学滇池学院课程：数字信号处理