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olivia-moreira | 2016-09-09 | General

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Analog and Digital. Analog and Digital Data & Signals. Periodic & Aperiodic Signals. Contents. Information can be voice, image, numeric data, characters or any message that is readable and has meaning to the destination . ID: 463044

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Slide1

SignalsAnalog and DigitalAnalog and Digital Data & SignalsPeriodic & Aperiodic Signals

Contents

Slide2Information can be voice, image, numeric data, characters or any message that is readable and has meaning to the destination Generally, the information is not in a form that can be transmitted over a LinkThe binary digits must be converted into a form that Transmission Medium can acceptThe data stream of 1s and 0s must be turned into Signals

Signals

Slide3ANALOGRefers to something that is ContinuousCONTINUOUS A set of specific points of data and all possible points between them

Analog

Slide4DIGITALRefers to something that is DiscreteDISCRETE A set of specific points of data with no points in between

Digital

Slide5Analog DataHuman VoiceAnalog ClockDigital DataData stored in the memory of a computerDigital Clock

Analog and Digital Data

Slide6It is a continuous waveform that changes smoothly over timeAs the wave moves from value ‘ A’ to value ‘B’, it passes through and includes an infinite number of values along its pathA digital signal is discrete. It can have only a limited number of defined values, often as simple as 1s and 0s The transition of a digital signal from value to value is instantaneous like a light being switched ON and OFF

ANALOG & DIGITAL Signal

Slide7Analog and Digital Signals

Slide8Periodic and Aperiodic Signals

Periodic

Signals

(Analog or Digital)

Aperiodic

Slide9A signal is called Periodic if it completes a pattern within a measurable time frame called a Period and then repeats that pattern over identical subsequent Periods.The completion of one full period is called a cycle.

Periodic Signals

Slide10Periodic Signal Example

Slide11An Aperiodic or Non-Periodic signal is the one that changes constantly without exhibiting a pattern or cycle that repeats over time

Aperiodic Signals

Slide12Aperiodic Signals

Slide13Analog signals can be classified into:Simple Analog Signal (Sine wave)Composite Analog Signal

Analog Signals

Slide14Simple Analog Signal

(Sine Wave)

Slide15Sine waves can be fully described:AmplitudePeriod / FrequencyPhase

Simple Analog Signal

(Sine Wave)

Slide16Amplitude of a signal is the value of the signal at any point on the waveIt is equal to the vertical distance from a given point on the wave form to the horizontal axisThe maximum amplitude of the sine wave is equal to the highest value it reaches on the vertical axisAmplitude measured in Volts, Amperes or Watts

Amplitude

Slide17Amplitude

Slide18Period: Amount of time ( in seconds) a signal need to complete one cycleFrequency: Number of cycles completed in one secondUnit of Period: Period is expressed in seconds

Period & Frequency

Slide19Period and Frequency

T= 1 / f OR f=1 / T

Slide20Seconds____HertzMilliseconds____KilohertzMicroseconds____MegahertzNanoseconds____GigahertzPicoseconds____Terahertz

Units of Period & Frequency

Slide21Example

A Sine wave has a frequency of 6 Hz. What is its period?Solution

Slide22Example

A Sine wave completes one cycle in 4 seconds. What is its frequency?Solution:

Slide23Another Way to Look at Frequency

Measurement of the rate of change

How fast the wave moves from its lowest to its highest point

A 40 Hz signal has half the frequency of a 80 Hz signal, therefore each cycle takes twice as long to complete one cycle

Changes in Short Time: High Frequency

Slide24Two Frequency Extremes

No change at all

Zero frequency

Instantaneous

changes

Infinite

frequency

Change in a short span of time means high frequency.

Change over a long span of time means low frequency.

Slide25Phase

Phase describes the position of the waveform relative to time zero

Phase describes the amount of backward or forward shift of the waveform

Measured in Degrees or Radians

Slide26It indicates the status of the first cyclePhase is measured in Degrees or Radians360 degrees – 2 pi RadiansA phase shift of 360 degrees correspond to a shift of a complete period

Phase

Slide27Phase

Slide28Example 4.7

A sine wave is offset of a cycle with respect to time zero. What is its phase?

Slide29Wavelength binds the period or the frequency of a simple sine wave to the propagation speed of mediumFrequency of signal is independent of the medium, while the wave length depends on both frequency and mediumWavelength is the distance a simple signal can travel in one period Wavelength = propagation speed * Period

Wavelength

Slide30Wavelength

Slide31Control of Signals

Signal can be controlled by three attributes:

Amplitude

Frequency

Phase

Slide32Control of Signals- Amplitude

Slide33Control of Signals- Frequency

Slide34Control of Signals- Phase

Slide35Time Domain plots show changes in signal amplitude w.r.t TimeIt is an Amplitude versus Time PlotPhase and Frequency are not explicitly measured on a Time domain plotTo show the relationship between amplitude and Frequency, we can use what is called a Frequency Domain Plot

Time and Frequency Domain

Slide36Time and Frequency Domain

Slide37Time and Frequency Domain Example

Slide38Second type of Analog Signals, that is composed of multiple sine wavesSo far we have been focused on simple periodic signals or sine wavesMany useful sine waves do not change in a single smooth curve b/w minimum and a maximum amplitude. They jump, slide , wobble and spikeAs long as as any irregularities are consistent, cycle after cycle, a signal is still PeriodicIt can be shown that any periodic signal no matter how complex can be decomposed into a collection of sine waves, each having a measurable amplitude, frequency & phaseWe need FOURIER ANALYSIS to decompose a composite signal into its components

Composite Signals

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