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For example, if x(t) represents the magnitude of the electric field component (in volts per meter) of an optical signal propagating through free space, then the dimensions of X(f) would become volt·seconds per meter and () would represent the signal's spectral energy density (in volts 2 ·second 2 per meter 2) as a function of frequency f (in ...
As the description implies, is the signal energy associated with each user data bit; it is equal to the signal power divided by the user bit rate (not the channel symbol rate). If signal power is in watts and bit rate is in bits per second, is in units of joules (watt-seconds).
As a physical example of how one might measure the energy spectral density of a signal, suppose () represents the potential (in volts) of an electrical pulse propagating along a transmission line of impedance, and suppose the line is terminated with a matched resistor (so that all of the pulse energy is delivered to the resistor and none is ...
In human engineering, signals are typically provided by a sensor, and often the original form of a signal is converted to another form of energy using a transducer. For example, a microphone converts an acoustic signal to a voltage waveform, and a speaker does the reverse. [1] Another important property of a signal is its entropy or information ...
Since the energy levels of electrons in atoms are discrete, each element and each molecule emits and absorbs its own characteristic frequencies. Immediate photon emission is called fluorescence, a type of photoluminescence. An example is visible light emitted from fluorescent paints, in response to ultraviolet . Many other fluorescent emissions ...
a signal is transmitted, with a long enough length so that the energy budget is correct; this signal is designed so that after matched filtering, the width of the intercorrelated signals is smaller than the width obtained by the standard sinusoidal pulse, as explained above (hence the name of the technique: pulse compression).
Energy from RF currents in conductors can radiate into space as electromagnetic waves (radio waves). [2] This is the basis of radio technology. RF current does not penetrate deeply into electrical conductors but tends to flow along their surfaces; this is known as the skin effect.
Electrical energy is distributed as alternating current because AC voltage may be increased or decreased with a transformer. This allows the power to be transmitted through power lines efficiently at high voltage, which reduces the energy lost as heat due to resistance of the wire, and transformed to a lower, safer voltage for use. Use of a ...