Electronic Systems. Dr. Kenneth Kin-Yip Wong. ENGG st Semester, Department of Electrical and Electronic Engineering

Transcription

1 Electronic Systems ENGG st Semester, 2011 Dr. Kenneth Kin-Yip Wong Department of Electrical and Electronic Engineering

2 Introduction Today H ENGG1015: Hybrid 1 semester L Recall that ENGG1015 is about a hybrid top- down introduction to EEE time Today: A brief detour to the bottom 1st semester, 2011 ENGG Dr. K. Wong 2

3 Course Topics High Level Today Applications Systems Digital Logic Image & Video Processing Computer & Embedded Systems Computer Network Mobile Network Combinational Logic Boolean Algebra Circuits Basic Circuit Theory Low Level Electrical Signals Voltage, Current Power & Energy 1st semester, 2011 ENGG Dr. K. Wong 3

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5 Electronic Systems Physical World Input Process Output Physical World All electronic/electrical systems must ultimately be dealing with the physical world: Temperature of the air, Time, Light, Sound, Human movement Hierarchy (the use of sub-system), might hide that fact, but the all systems do interact with the physical world 1st semester, 2011 ENGG Dr. K. Wong 5

6 System Components - Input Sound Temperature Light Pressure Physical World Input Voltage (V) Current (I) () Resistance (R) Capacitance, Inductance Convert physical quantities into internal quantities that are easy to manage In EEE, it usually means converting a physical quantity into electrical signals, such as voltage (V), current (I), resistance (R), etc Examples A microphone translates movement of air in the form of air pressure into voltage A light sensor translate light intensity (lumens) into resistance A thermistor translates temperature into resistance 1st semester, 2011 ENGG Dr. K. Wong 6

7 System Components - Output Voltage (V) Current (I) () Resistance (R) Capacitance, Inductance Output Physical World Sound Temperature Light Pressure Convert internal quantities that are easy to manage into physical quantities that interact with the physical world Examples A speaker translates voltage values (V) into movement of air in the form of air pressure that t generate sound A light bulb that turns current values (I) into light A motor that drives a wheel to spin A solenoid that generates a pulling force on a shaft 1st semester, 2011 ENGG Dr. K. Wong 7

8 System Components - Processing Process Performs the intended function of the system. Examples Amplifies the electrical signal from a microphone Control the power of the motor of a fan depending on input voltage Slightly more complex example: Mixes the voltage input from two different microphones, amplifies the signal, and control the voltage that will drive a signal indicator and output speaker 1st semester, 2011 ENGG Dr. K. Wong 8

9 Complex Systems (1) Top-Level System Subsystem A Subsys B Subsys B-1 Subsys B-2 Subsys C Decompose a system into multiple sub-systems Each sub-systemssystems can be decomposed into more sub- systems A top-down approach Compose larger systems by connecting smaller subsystems Each composed system can be used to compose even bigger systems A bottom-up approach The organization of sub-systems form a hierarchy 1st semester, 2011 ENGG Dr. K. Wong 9

10 Complex Systems (2) Top-Level System Subsystem A Subsys B Subsys B-1 Subsys B-2 Subsys C Engineers usually represent each sub-system as a block, forming block diagrams. The boundary of each sub-system is somewhat arbitrary Up to the engineering team But the key is to have a clean and well-defined interface 1st semester, 2011 ENGG Dr. K. Wong 10

11 Quick Summary Quiz (1) Which of these statements is false? Smaller systems are easier to design and develop. Smaller systems are more difficult to debug if problem arises. Each sub-team may be responsible for one specific sub-systems, systems making management easier. Subdividing idi a large system helps to isolate problems at sub-system boundaries. 1st semester, 2011 ENGG Dr. K. Wong 13

12 Quick Summary Quiz (2) Which item is a characteristic of a topdown approach? Driven by system requirement Driven by component integration Construct t system by composing smaller parts Synthesis new ideas from existing components 1st semester, 2011 ENGG Dr. K. Wong 14

13 Analog and Digital In electronic systems, the processing and transfer of a signal can broadly classified as analog or digital in nature. Possible to mix-and-match An analog system processes signals with continuous values e.g. Temperature is now CC A digital system processes signals with discrete values e.g. The time now is 2:32pm, temperature is 24 C 1st semester, 2011 ENGG Dr. K. Wong 15

14 Analog Systems An analog electronic system processes signals with continuous values Usually processes in continuous time as well Some sub-systems work with continuous values in discrete time The exact value of the signal matters No approximation needed 1st semester, 2011 ENGG Dr. K. Wong 16

15 Analog Systems - Pros sound wave Sound wave V Process V Output Most physical quantities are continuous in nature: e.g. temperature, time, humidity, pressure The fundamental electronic quantities are also continuous in nature: Voltage, Current, Resistance Analog processing is the most natural way of processing information from the physical world Fastest way to process any signal 1st semester, 2011 ENGG Dr. K. Wong 17

16 Analog Systems - Cons Since exact value of a signal is needed, any degradation of signal will be reflected at the output. Examples: Interference, sometimes called noise, from outside the system: Radio frequency interference (RFI) Noise within the system: Electric component s behavior changes due to temperature change Thermo noise in circuits Non-ideal electronic components A resistor s true value is never what it is designed Degradation of components over time 1st semester, 2011 ENGG Dr. K. Wong 18

17 Analog Systems Cons (cont d) Very difficult to store any exact value, in continuous time Difficult to process signals based on previous values Echo cancellation Reverb Difficult to transport signals because signals degrades over any medium of transfer, especially in long distances Old TV systems suffer from ghost images Radio station not received well Note: it is difficult, not impossible in above 1st semester, 2011 ENGG Dr. K. Wong 19

18 Digital Systems A digital electronic system processes signals with discrete values in discrete time The exact values of the input signal at discrete point in time are quantized into discrete values e.g. all values are stored as integers only CC 25 CC The process of obtaining data at discrete time or space is called sampling. More on sampling & quantization later The continuous values of the input signals represented by a series of finite number of discrete values. 1st semester, 2011 ENGG Dr. K. Wong 20

19 Digital Processing Systems Analog Systems Physical World Input Process Output Physical World 3, 5, 6, 7 7.2, 6.1, 4.8, 3.14 Digital Systems ADC DAC 1st semester, 2011 ENGG Dr. K. Wong 21

20 Digital Systems Pros Discrete values are easy to store, transport No degradation over time & space Easy to process back-in-time Knowing the past make predicting the future a lot easier Enable very powerful and complicated processing of input e.g. complex logic, encryption, compression, etc Immune to a lot more interferences from inside and outside of the system than an analog system E.g. RFI, circuit noise, non-idealistic circuits and degradation over time Note: you can still interfere a digital system with enough power 1st semester, 2011 ENGG Dr. K. Wong 22

21 Quick Summary Quiz Consider an analog and a digital system, which of them is better in: processing the exact value of a physical phenomenon? processing the exact value of a physical phenomenon 1 day after the phenomenon has happened? producing the exact same result in two different occasions? Which one is better? e 1st semester, 2011 ENGG Dr. K. Wong 24

22 Input Stage: ADC Digital gta Systems Input Process Output Physical World Input Process Output Physical World 3, 5, 6, 7 7.2, 6.1, 4.8, 3.14 ADC DAC 1st semester, 2011 ENGG Dr. K. Wong 30

23 Input Stage: ADC Digital gta Systems Input Process Output Physical World ADC Physical World 3, 5, 6, 7 7.2, 6.1, 4.8, 3.14 ADC DAC 1st semester, 2011 ENGG Dr. K. Wong 31

24 Analog to Digital Conversion The process of converting analog information into digital representation is referred as analog to digital conversion The circuit that performs the conversion is called an analog to digital convertor (ADC). The reverse process is called digital to analog conversion, using a digital to analog convertor (DAC). Today: We ll look at how to build a 1-bit ADC circuit Review of basic circuit design Extremely useful for project 1st semester, 2011 ENGG Dr. K. Wong 32

25 1-bit ADC v in ADC out Recall that an ADC converts (quantizes) an analog signal into digital representation An 1-bit ADC quantizes the analog input into a two possible outcomes hot VS cold analog signal is presented VS not presented input voltage is higher than certain value VS otherwise. Use a single binary bit to represent 2 values In other word, an 1-bit ADC makes a binary decision about the analog input. 1st semester, 2011 ENGG Dr. K. Wong 33

26 1-bit ADC: logical design Essentially, an 1-bit ADC is a comparator Compares to a built in threshold Compares to a outside input value An electronic ADC implements this concept using electronic circuits 1st semester, 2011 ENGG Dr. K. Wong 34

27 1-bit ADC (cont d) out = 1 if v in > v t out = 1 if v in > v ref v in out v in v ref out Threshold Comparator In the simplest case, an 1-bit ADC can be thought as a thresholding circuit, If the input voltage is higher than a built-in threshold v t, then the output is 1, otherwise the output is 0. In a slightly more elaborated design, an 1-bit ADC can be implemented as a comparator circuit that compares the value of the ADC input v in to another reference input (v ref ). 1st semester, 2011 ENGG Dr. K. Wong 35

28 Peeling an ADC onion 1 or 0 v in ADC out 1 layer down v in ADC v ref 1 or 0 out Note that what we have done so far was indeed gradually unveiling the inner details of an ADC From the abstract t concept of analog-to-digital it l conversion, we are moving downward to unveil more implementation details with the underlying circuits A thresholding or comparator circuit Next: What are those 1 s and 0 s? 1st semester, 2011 ENGG Dr. K. Wong 36

29 I/O Characteristics of 1-bit ADC out v in v ref time 1st semester, 2011 ENGG Dr. K. Wong 37

30 Implementing Logic Levels The 0 s and 1 s in previous slides are merely symbols to represent two logical states e.g. the value 1/0, high/low, on/off, true/false, hot/cold In actual circuit implementations, these 0 s and 1 s 1s are represented by the voltage (potential) presented at the output. NOTE: There are other circuit implementations that uses current at the output node to represent 0 s and 1 s, but we will focus in voltage here. What voltage should be used to represent 1 and what voltage to represent 0? 1st semester, 2011 ENGG Dr. K. Wong 38

31 Logic Families There are industrial standards on the voltage levels for representing logic levels in discrete components. Sometimes referred as I/O standards. Image source: 1st semester, 2011 ENGG Dr. K. Wong 39

32 Own standard? You can have your own standard when you build your own circuit, e.g.: digital VLSI designs e.g. 3.3V, 2.5V, 1.5V, 1.2V Your class project e.g. 12V Usually uses the maximum allowable voltage as 1, and minimum allowable voltage as 0 Customary to label the max voltage as V cc or V dd Minimum allowable voltage usually is 0 volt (not 0 ). 1st semester, 2011 ENGG Dr. K. Wong 40

33 Realistic Circuit I/O 1-bit ADC out v in v ref 0 time 1st semester, 2011 ENGG Dr. K. Wong 41

34 Real Circuits out v in v ref 0 time 1st semester, 2011 ENGG Dr. K. Wong 42

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36 Tutorials Tutorials have started on Tuesday (Sep 6) and will repeat on Monday (Sep 12) with same content You may attend either class A or class B s tutorial session First tutorial s topic: review on circuits Extremely useful for your project 1st semester, 2011 ENGG Dr. K. Wong 44

37 Pre-Project Project Lab 2-4 pm Monday to LG205 CYC building Starts next week Compulsory Graded Mon-Fri: Fi 32 students t (max) per session READ the safety regulation before the lab#1 1st semester, 2011 ENGG Dr. K. Wong 45

38 Pre-Project Project Lab Signup Need to sign up for the lab session that you intend to join Signup link active starting 2pm Friday, Sep 9 for 24 hours Will be posted on course website Optional group signup If you have already found your partners for project, signup to the SAME session Project group will be formed within the lab session Need login/password from EEE CSG for signup Have already sent to your HKU account on Sep 1 If NOT yet, send to support@eee.hku.hk Or visit Rm 804, CYC building First-come, first-served 1st semester, 2011 ENGG Dr. K. Wong 46

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40 The Marshmallow Challenge 18 minutes Teams of four (4) Tallest freestanding structure (on ground) Marshmallow on top (intact!!) com 1st semester, 2011 ENGG Dr. K. Wong 48

41 In conclusion All electronic/electrical systems can be divided id d into three main sub-systems: input, process, output Analog systems manipulate analog signals throughout Digital systems handles digital data in process stage 1-bit ADC can be implemented using simple comparator Logical values electrical values 1st semester, 2011 ENGG Dr. K. Wong 49