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chap2.pdf - Transmission Fundamentals Chapter 2...

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Transmission Fundamentals Chapter 2
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Electromagnetic Signal Function of time Can also be expressed as a function of frequency Signal consists of components of different frequencies
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Time-Domain Concepts Analog signal - signal intensity varies in a smooth fashion over time No breaks or discontinuities in the signal Digital signal - signal intensity maintains a constant level for some period of time and then changes to another constant level Periodic signal - analog or digital signal pattern that repeats over time s ( t + T ) = s ( t ) - ∞ < t < +∞ where T is the period of the signal
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Time-Domain Concepts Aperiodic signal - analog or digital signal pattern that doesn't repeat over time Peak amplitude ( A ) - maximum value or strength of the signal over time; typically measured in volts Frequency ( f ) Rate, in cycles per second, or Hertz (Hz) at which the signal repeats
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Time-Domain Concepts Period ( T ) - amount of time it takes for one repetition of the signal T = 1/ f Phase ( ) - measure of the relative position in time within a single period of a signal Wavelength ( ) - distance occupied by a single cycle of the signal Or, the distance between two points of corresponding phase of two consecutive cycles = ᴠ . T
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Sine Wave Parameters General sine wave: s ( t ) = A sin(2 f t + ) Figure 2.3 shows the effect of varying each of the three parameters: (a) A = 1, f = 1 Hz, = 0; thus T = 1s (b) Reduced peak amplitude; A =0.5 (c) Increased frequency; f = 2, thus T = 1/2 (d) Phase shift; = /4 radians (45 degrees) note: 2 radians = 360 ° = 1 period
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Sine Wave Parameters
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Time vs. Distance When the horizontal axis is time , as in Figure 2.3, graphs display the value of a signal at a given point in space as a function of time With the horizontal axis in space , graphs display the value of a signal at a given point in time as a function of distance At a particular instant of time, the intensity of the signal varies as a function of distance from the source
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Frequency-Domain Concepts Fundamental frequency - when all frequency components of a signal are integer multiples of one frequency , it’s referred to as the fundamental frequency Spectrum - range of frequencies that a signal contains Absolute bandwidth
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