Signals 1 Signals Introduction n Analog and Digital

Signals 1

Signals Introduction n Analog and Digital n 2

Introduction n Information can be in the form of data, voice, picture, etc. Internally (in a computer) it is represented in the form of a stream of 1 s and 0 s When it is transmitted across network links, it is converted into a form that transmission media can accept – Electromagnetic signals 3

Analog and Digital n n Data and Signals can be represented in analog or digital form Analog – Refers to something that is continuous – A set of specific points of data and all possible points between n Digital – Refers to something that is discrete – A set of specific points of data with no other points between 4

Analog and Digital n Analog and Digital Data : examples – Analog data n Human voice n A continuous wave is created n Converted to analog signal – Digital data n 0/1 data stored in a computer n converted into digital signal 5

Analog and Digital n n Analog and Digital Signals Analog signal – A continuous wave form – There are infinite values along a path 6

Analog and Digital n Digital signal – Discrete – It has a limited number of defined values (0/1) 7

Analog and Digital Signals 8

Periodic Signals A periodic signal consists of a continuous repeated pattern n The period of a signal (T) is expressed in seconds n 9

Periodic Signals 10

Aperiodic Signals Signal has no repetitive pattern 11

Analog Signals Simple analog signal : a sign wave form 12

Analog Signals : Sign Wave n 3 characteristics of a sign wave – Amplitude n The height of the signal n The unit : volt, ampere, watt – Period and frequency n The amount of time (in seconds) a signal needs to complete one cycle n Frequency = the number of periods in one second (number of cycles per second( 13

Amplitude at time t 1 Maximum Amplitude t 1 Minimum Amplitude 14

Frequency is a rate of change with respect to time n Change in a short span of time means high frequency n Change in a long span of time means low frequency n If a signal does not change at all, its frequency is zero n 15

Period and Frequency 3 periods in one second Frequency = 3 Hz One second Period = 1/3 second 16

Phase Describes the position of the waveform relative to time zero n Phase is measured in degrees or radius (360 degrees is 2 Pi radians) n 17

Phases 18

Amplitude Change 19

Frequency Change 20

Phase Change 21

Time and Frequency Domains 1 second 12 Frequency = 7 Hz 12 7 22

Time and Frequency Domains n A low frequency signal in the frequency domains corresponds to a signal with a long period in the time domain and vice versa n A signal that changes rapidly in the time domain corresponds to high frequency in the frequency domain 23

Examples 24

Signal with DC Component 25

Complex Waveform 26

Bandwidth 27

Digital Signal 28

Amplitude, Period, and Phase for a Digital Signal 29

Bit Rate and Bit Interval 30

Harmonics of a Digital Signal 31

Exact and Significant Spectrums 32

Bit Rates and Significant Spectrums 33

Bandwidth and Data Rate 34

Example 35

36