1 Signals

2 Signals Introduction Introduction Analog and Digital Analog and Digital

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

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

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

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

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

8 Analog and Digital Signals

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

10 Periodic Signals

11 Aperiodic Signals Signal has no repetitive pattern

12 Analog Signals Simple analog signal : a sign wave form

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

14 Amplitude Minimum Amplitude Maximum Amplitude t1 Amplitude at time t1

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

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

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

18 Phases

19 Amplitude Change

20 Frequency Change

21 Phase Change

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

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

24 Examples

25 Signal with DC Component

26 Complex Waveform

27 Bandwidth

28 Digital Signal

29 Amplitude, Period, and Phase for a Digital Signal

30 Bit Rate and Bit Interval

31 Harmonics of a Digital Signal

32 Exact and Significant Spectrums

33 Bit Rates and Significant Spectrums

34 Bandwidth and Data Rate

35 Example

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