Noise and Distortion Lecture Notes

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Flashcards about Noise and Distortion in communication systems.

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20 Terms

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Noise

An electronic signal made up of many random frequencies at many amplitudes added to a radio or information signal, showing up as random AC voltage.

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Signal Noise

Unwanted interference that degrades a communication signal and affects both analog and digital signals.

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Industrial Noise

Produced by manufacturing equipment, automotive ignition systems, generators, and electric motors, causing high voltages or currents to be switched, creating transients.

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Atmospheric Noise

Electrical disturbances that happen naturally in the Earth's atmosphere, often from lightning, impacting signals with frequencies below 30 MHz.

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Extraterrestrial Noise

Noise that comes from the sun, which radiates a wide range of signals in a broad noise spectrum with an 11-year cycle, or from stars outside the solar system, disrupting the 10 MHz to 1.5 GHz range.

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Internal Noise

Noise that comes from electronic components in a receiver, such as resistors, diodes, and transistors; often low-level but can interfere with weak signals.

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Thermal Noise

Caused by thermal agitation, the random motion of free electrons in a conductor caused by heat, leading to a small voltage production across conductor components.

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White Noise

Thermal agitation, random motion of free electrons in a conductor caused by heat. Believed to contain all frequencies randomly happening at random amplitudes.

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Semiconductor Noise

Noise that comes from components such as diodes and transistors, including shot noise, transit-time noise, and flicker noise.

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Intermodulation Distortion

Comes from generating new signals and harmonics caused by circuit nonlinearities, occurring when two or more signals are used in a non-linear circuit.

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Noise Factor (NR)

Expressed as noise figure and noise factor, it is the ratio between S/N power at the input and S/N power at the output.

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Noise Figure (NF)

When the noise factor is expressed in decibels.

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Distortion

A condition that adds unwanted change in the signal.

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Selectivity

Communication receiver's ability to identify and select a desired signal from others present in the frequency spectrum.

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Sensitivity

Lets communication receivers pick up weak signals and provide sufficient amplification to recover the modulating signal.

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Shape Factor

Expressed as the ratio of the 60-dB down bandwidth to the 6-dB down bandwidth or the bandwidths of the receivers at two levels of attenuation.

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Minimum Discernible Signal (MDS)

The input signal level that is almost equal to the average noise floor of the receiver, expressed in dBm.

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Radio Emission Code Designations

Assigned to many types of signals and are comprised of a capital letter, a number, and lowercase subscript letters, defining the modulation type, transmitted information type, and specifics, respectively.

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ITU Emission Designation

Used to describe a signal with more variations and is used by the International Telecommunication Union (ITU).

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BBBB

Defines the bandwidth in the ITU Emission Designation system