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數位訊號處理概論Introduction to Digital Signal Processing:
Topic 1 Introduction(Textbook Chap 1)
Meng-Lin Li (李夢麟), Ph. D.
Department of Electrical Engineering
National Tsing Hua University
mailto:[email protected]
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What Will You Learn?Take Home Quizzes
l Limitations and drawback of ANAGLOG signal processing (ASP)?
l How DSP affects circuit design or circuit/system structure nowadays?
l Advantage of DSP over ASP?
l Limitations of DSP?
l Why I arrange the topics in the order shown in the syllabus?
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Definition of Digital Signal Processing
l That discipline which has allowed us to replace a circuit previously composed of a capacitor and a resistor with two antialiasing filters, and A-to-D and a D-to-A converter, and a general purpose computer (or array processor) so long as the signal we are interested in does not vary too quickly.
Thomas P. Barnwell, 1974
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What is “Analog signal”? and
What is “Digital/Discrete signal”?
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Analog vs. Discrete-Time and Digital Signals
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Analog vs. Discrete-Time and Digital Signals
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Analog vs. Digital/Discrete Signals
Analog signal
l Signals continuous in time and amplitude
l Electrical signals
n Voltages, currents
l Mechanical signals
n Velocities, forces
l Acoustic signals
n Vibrations, sound waves
l Signals related to physical sciences
n Pressures, temperature
Digital signal
l Signals represented by numbers in a computer (or in a specialized digital hardware)
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How to Obtain Analog Signal and
What is Analog Signal Processing?
l Converted to voltages or currents by sensors or transducers in order to be processed electrically
l Analog signal processing (ASP) involves operations such as amplification, filtering, integration, and differentiation, as well as various forms of nonlinear processing (squaring, rectification)
l ASP of electrical signals is typically based on electronic amplifiers, resistors, capacitors, inductors, and so on
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Limitations and Drawback of ANAGLOG Signal Processing (ASP) of Electrical Signals
l Accuracy limitations
l Limited repeatability
l Sensitivity to electrical noise
l Limited dynamic range of voltage and currents
l Limited processing speeds due to physical delays
l Lack of flexibility to specification changes in the processing functions
l Difficulty in implementing nonlinear and time-varying operations
l High cost and accuracy limitations of storage and retrieval of analog information
Boaz Porat’s DSP book
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Definition of Digital Signal Processing
l That discipline which has allowed us to replace a circuit previously composed of a capacitor and a resistor with two antialiasing filters, and A-to-D and a D-to-A converter, and a general purpose computer (or array processor) so long as the signal we are interested in does not vary too quickly.
Thomas P. Barnwell, 1974
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Digital Signal Processing (DSP)
l Based on representing signals by numbers in a computer and performing various numerical operations in these signals
l Operations include, but are not limited to, additions, multiplications, data transfers, and logical operations
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Art of Aliasing Distortion
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Veebot
http://spectrum.ieee.org/robotics/medical-robots/profile-veebot
https://www.youtube.com/watch?v=s30FPobi9iA#t=21
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Cyborg Cockroach
(Image: Carlos Sanchez, Mechanical Engineering, Texas A&M University)
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Implementation of a General DSP System
l 1. To convert analog signals (from sensors) into digital information, in the form of a sequence of binary numbers (sampling and analog-to-digital conversion (ADC))
l 2. To perform numerical operations on the digital information, either by a computer or special-purpose digital hardware
l 3. To convert the digital information, after being processed, back to an analog signal (digital-to-analog conversion (DAC) and reconstruction)
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Four Basic DSP Schemes
Boaz Porat’s DSP book
Digital recording and playback of music
Touch-tone system of telephone dialing
Text-to-speech system
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Analog, Interface, and Digital Systems
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What Parameter ConnectsReal World and Digital World?
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Interface Systems: ADC
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Interface Systems: DAC
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How DSP Affects Circuit Design or Circuit/System Structure Nowadays?
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DSP Flow Nowadays
Real time?
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Block Diagram of A Digital Cell Phone
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Limitations and Drawback of ANAGLOG Signal Processing (ASP) of Electrical Signals
l Accuracy limitations
l Limited repeatability
l Sensitivity to electrical noise
l Limited dynamic range of voltage and currents
l Limited processing speeds due to physical delays
l Lack of flexibility to specification changes in the processing functions
l Difficulty in implementing nonlinear and time-varying operations
l High cost and accuracy limitations of storage and retrieval of analog information
Boaz Porat’s DSP book
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Advantages of DSP over ASP
l Accurate to any desired degree (at least theoretically), by choosing a suitable word length
l Perfectly repeatable
l Sensitivity to electrical noise is extremely low (but not nil)
l Use of floating point makes it possible, by choosing the word length, to have a practically infinite dynamic range
l Speed is a limiting factor in computers as well as in analog devices, but advances in technology push the limit forward
l Changes in processing functions can be made through programming
Boaz Porat’s DSP book
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Advantage of DSP over ASP
l Implementing nonlinear and time-varying processing (e.g., adaptive filtering) is conceptually easy (via programming)
l Digital storage is cheap and flexible
l Digital information can be encrypted for security, coded against errors, and compressed to reduce storage and transmission costs
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Limitations of DSP
l Sampling inevitably leads to loss of information, which can be minimized by careful sampling but cannot be completely avoided
l A/D and D/A conversion hardware may be expensive especially if great accuracy and speed are required, and it is never free of noise and distortion
l Software not necessarily becomes cheaper and more sophisticated every year (more and more often to be the main bottleneck in developing DSP applications)
l In certain applications, notably processing of RF signals, digital processing still cannot meet speed requirements
Boaz Porat’s DSP book
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Applications of DSP
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Why I Arrange the Topics in the Order Shown in the Syllabus?
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Syllabus
l Topic 0 Tutorial on MATLAB
l Topic 1 Introduction of DSP
l Topic 2 Review of frequency-domain analysis
n Discrete-time (DT) signals and systems
n Fourier representation of signals
l Topic 3 Sampling and reconstruction (1D & 2D, Practical issue)
n Aliasing
n DT processing of continuous-time (CT) signals
n Sampling rate conversion
l Topic 4 Discrete Fourier transform (DFT) and practical spectral analysis
n DFT
n Linear convolution using DFT
n Practical spectral analysis
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Syllabus
l Topic 5 Miscellaneous - More about Convolution, Filter Design, FT View of Diffraction, and Matrix-based FFT
l Topic 6 Revisit of z-Transform
n Structures for discrete-time systems
n From analysis to system design (revisit of linear phase system, and how poles and zeros affect the frequency response)
l Topic 7 Design of FIR and IIR filters
n Filter design and implementation with linear phase
n FIR filter design
n IIR filter design (if we have time)
l Selected advanced topics (if we have time/seminar talks):
n Spectral analysis of random signals
n Adaptive filtering
n Biomedical imaging
n Compressive sensing
n Machine learning
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DSP Flow Nowadays
Real time?
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Have You Learned?
l Limitations and drawback of ANAGLOG signal processing (ASP)?
l How DSP affects circuit design or circuit structure nowadays?
l Advantage of DSP over ASP?
l Limitations of DSP?
l Why I arrange the topics in the order shown in the syllabus?
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Take Home Quizzes
l Think about how to write a program to perform continuous time Fourier transform (CTFT)
n Generate a cosine signal (as a function of time) with a designated frequency
n Test your CTFT codes with the cosine signal
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數位訊號處理概論Introduction to Digital Signal Processing:
Topic 1 Introduction(Textbook Chap 1)
Meng-Lin Li (李夢麟), Ph. D.
Department of Electrical Engineering
National Tsing Hua University
mailto:[email protected]