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The bandwidth of a transmission medium

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• Acceptable level of power loss

  • Acceptable loss threshold (set by electrocal engineers):

    power(output signal) ----------------------- ≥ ln 2 ~= 0.7 power(input signal)

    This value is known as the half-power point: click here

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• Range of acceptable frequencies of a transmission media

  • Definitions:

    Let f0 = the low end frequency such that: power(output signal) ----------------------- = ln 2 = 0.7 power(input signal) Let f1 = the high end frequency such that: power(output signal) ----------------------- = ln 2 = 0.7 power(input signal)

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  • Graphically: the frequencies f₀ and f₁ are defined as follows:

  • Fact:

    Electrical signals (= alternating current)) that have a frequency between f0 and f1 will pass through the transmission medium with relatively little loss of energy

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• Bandwidth of a communication medium

  • Definition: bandwidth of a communication medium:

    Bandwidth of a communication medium (a.k.a., transmission channel) = f1 − f0 Graphically:

    Fact:

    There is a direct relationship between Bandwidth of a communication channel                   and        Maximum transmission rate of the communication channel (= how fast you can transmit communication channel)

    This relationship is called the Shannon formula and will be discussed next