CHAPTER 1 Signals and Signal Processing

Wang Weilian [email protected]

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

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Characterization and Classification of Signals

•

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

Signals and Signal Processing 3

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

Signals and Signal Processing 4

Typical Signal Processing Operations

•

Elementary Time-Domain Operations

–

Scaling:

  –

Integration:

–

Differentiation:

–

Delay operation:

–

Addition:

 

t

 

x d

 

dx t



dt t

0

) ( )



( )

 –

Product of two signals:



( ) ( )

2

( )

云南大学滇池学院课程：数字信号处理

Signals and Signal Processing 5

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

Signals and Signal Processing 6

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

    

h HT

(

t



h HT

     1

t

•

h HT

( ) •

H HT

(

j

)

The complex signal is

  

j

,  

j

,   0  0   云南大学滇池学院课程：数字信号处理

Signals and Signal Processing 7

Typical Signal Processing Operations

•

Modulation

    

A

cos(



0

t

)

•

Demodulation

   

A

cos(



0

t

)

低通滤波器 

0

t

)



A

2

云南大学滇池学院课程：数字信号处理

Signals and Signal Processing 8

Typical Signal Processing Operations

• • •

Multiplexing and De-multiplexing

–

For an efficient utilization of a wideband transmission channel Quadrature Amplitude Modulation

 ( )cos( 0

t

)

Signal Generation

( )sin(  0

t

) –

Square waves

–

Triangular waves

–

White noise

云南大学滇池学院课程：数字信号处理

Signals and Signal Processing 9

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

Signals and Signal Processing 10

Examples of Typical Signals

•

Images Original Image

云南大学滇池学院课程：数字信号处理

Complement Image Signals and Signal Processing 11

• • • • •

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

Signals and Signal Processing 12

Why Digital Signal Processing

•

DSP everywhere

云南大学滇池学院课程：数字信号处理

Signals and Signal Processing 13

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

Signals and Signal Processing 14

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

Signals and Signal Processing 15

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

Signals and Signal Processing 16