Engineering edcational

1. Chapter One Prologue
1
1.0 Scope and Goals
1.1 Signal Processing
1.2 Illustrative Systems
1.3 Modeling
Contents of this Chapter:

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1.0 Introduction: Scope and Goals
• The scope of electronic circuits
Science，Engineering，Medicine，Maintenance，
Espionage
......
• The goals of this course
1. Introducing the fundaments of circuit's analysis and
synthesis.
2. Introducing the principle of the construction of
electronic system.
3. Introducing the basic applications of electronic circuits.

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1.1 SIGNAL PROCESSING
1.1.1 What is a signal?
• Information
The uncertain quantities for the receivers.
For example, news involves some unknown message, so we
can say that it has information. If someone told you "news"
you had known, the "news" would have not any information
• Signal
Some physical variables carried information.
Such as sound, images, text, voltage, current, etc. In
electronic system, signals are general voltage or current.
Signal can be classified two kinds

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1.1.2 Analog and Digital Signals
• Analog Signal
The signal (voltage or current) varies continuously with
time. For example
• Digital Signal
The signal has only two possible values, 0, 1. And the
signal can only change its value in discrete time points. For
example

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1.1.3 Signal Processing Systems
• The dialog of signal processing system

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• Input signals
1. Analog input signal, come from analog transducers, such as
thermocouples
2. Digital input signal, come from computer or other digital system.
• Signal processing module
1. Analog sub-system processes the analog signals.
2. Digital sub-system processes the digital signals.
• A/D and D/A conversion
1. A/D analog signal To digital signal (Lossless)
2. D/A digital signal To analog signal (Lossless)
• Output signal
1. Analog output signal to analog device for displaying, controlling.
2. Digital output signal to computer or digital device for displaying,
controlling, etc.

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1.2 Illustrative Systems
• A Communications System
An AM broadcast communication system调幅广播通信系统

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Transmitting system is called AM transmitter (调幅发射机）
Receiving system is called AM receiver (调幅接收机）
AM —— Amplitude Modulation（调幅），the amplitude of RF
signal varies according to the magnitude of a lower-frequency
signal (audio, corresponding to audible frequencies).
FM —— Frequency Modulation (调频），the frequency of RF signal
varies according to the magnitude of a lower-frequency signal
(audio, corresponding to audible frequencies).
RF —— Radio frequency (射频），it can be radiated and inducted by
an antenna. Each broadcast station is assigned its own radio
frequency. In our country the RF of AM broadcast is from 530 kilo
Hz to 1600 kilo Hz, and the RF of FM broadcast is from 88 million
Hz to 108 million Hz,

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Transmitter发射机
Control the amplitude of the RF signal using the input signal;
Drive the output device (the antenna) with RF current to
produce electromagnetic waves radiating into space.
Receiver接收机
Amplify the signal obtained from the antenna;
Filter the desired radio frequency signal from the signals of all
other broadcast stations;
Recover or select the audio signal from the amplitude variations
of the radio frequency signal;
Drive a loudspeaker with the recovered audio signal.

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• A Measurement System
The purpose of a measurement system is to acquire information
from suitable transducers(传感器) about the behavior of some
physical system and to display this information to the observer.

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• Transducer—— pair of thermocouple junctions, one attached to
the object whose temperature is to be measured, the other
submerged in an ice bath (to establish a stable reference point 0ºC)
• Input signal—— a voltage generated by the transducer depending
on the temperature difference between the object to be measured
and the reference point.
• Amplifier—— amplify the input analog voltage signal to a
sufficient amplitude.
• Linearizer—— linearize the analog voltage signal so that which is
exactly proportional to the temperature.
• A/D Converter—— convert the linearized analog voltage to digital
form.
• Digital display register数字显示寄存器—— register and display
the digital signal produced by A/D converter. The digital signal in
the register is refreshed periodically.

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1.3 Modeling
• Why modeling
1. Practical components in real electronic system differ in thousands
of ways.
2. The main characteristic of real components can be presented with
some basic functions.
3. The basic laws and theories of electrical networks should have
been universal
• How modeling
1. Define some basic ideal components called component model (the
less the better): such as resistor, capacitor, and inductor.
2. According to the main characteristic of real device, present the real
device by a combination of component models.