1. CHAPTER 1 Signals and Signal Processing
Wang Weilian
School of Information Science and Technology
Yunnan University

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

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

14. 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

15. 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

16. 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