Noise and Distortion Lecture Notes

Flashcards about Noise and Distortion in communication systems.

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.

Signal Noise

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

Industrial Noise

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

Atmospheric Noise

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

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.

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.

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.

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.

Semiconductor Noise

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

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.

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.

Noise Figure (NF)

When the noise factor is expressed in decibels.

Distortion

A condition that adds unwanted change in the signal.

Selectivity

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

Sensitivity

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

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.

Minimum Discernible Signal (MDS)

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

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.

ITU Emission Designation

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

BBBB

Defines the bandwidth in the ITU Emission Designation system