Glossary of  Terms (Electronics)

• Absorption: Attenuation of an electromagnetic wave due to dissipation of its energy, as by production of heat. (Penguin Dictionary of Electronics)

• Audio noise: In audio, recording, and broadcast systems audio noise refers to the residual low level sound (usually hiss and hum) that is heard in quiet periods of programme. It can also refer to the unwanted residual electronic noise that gives rise to "hiss".

• Balun: Balancing transformer. Used to couple a balanced impedance (for instance, antenna) to an unbalanced charge (for instance, coaxial cable).

• Barkhausen noise: discovered in 1919 by the German physicist Heinrich Barkhausen. Ferromagnetic materials consist of domains (small magnetic regions resembling individual bar magnets). Each domain is magnetized along a certain crystallographic direction. When the magnetizing flux is steadily increased, the magnetization proceeds as a series of finite jumps, caused by rapid rotation or changes of size of magnetic domains. The amount of Barkhausen noise for a given material is sensitive to changes in microstructure (amount of impurities, crystal dislocations, etc.) and can be a good indication of mechanical properties of the material. Hence, the Barkhausen noise can be used as a method of non-destructive testing of the degradation of mechanical properties in magnetic materials subjected to cyclic mechanical stresses or high radiation doses.

• Carbon Nanotube (CNT): Two definitions are available:

1. A fullerene molecule having a cylindrical or toroidal shape.

2. A carbon molecule that resembles a cylinder made out of chicken wire one to two nanometers in diameter by any number of millimeters in length.

Two categories of carbon nanotubes are fabricated: a) Single-walled nanotubes (SWNTs) use a single sheath of graphite one atom thick, called "graphene." b) Multiwalled nanotubes (MWNTs) are constructed of multiple cylinders, one inside the other. (www.answers.com)

• Colors of noise:

1. White noise It is a signal (or process), named by analogy to white light, with equal energy per cycle (Hertz), ideally extending to infinity. This produces a flat frequency spectrum in linear space. In other words, the signal has equal power in any band of a given bandwidth.

2. Pink noise This kind of noise occurs in many physical, biological and economic systems. Equally called 1/f noise, its power spectral density is linear in logarithmic space, hence each octave carries an equal amount of noise power. The name arises from being intermediate between white noise (1/ƒ⁰) and red noise (1/ƒ²).

3. Brown(ian) noise The term Brown(ian) noise does not refer to the colour “brown”, but to botanist Robert Brown (1773 – 1858) who discovered “Brownian movement” (random walk) of pollen particles in a fluid. Also called "red noise", when relating to the ambient noise of distant underwater objects. It refers to noise having a frequency spectrum with a power density which decreases 6 dB per octave with increasing frequency (density proportional to 1/f ²) over a frequency range which does not include DC. This kind of noise can be generated by an algorithm which simulates Brownian motion or by integrating white noise.

4. Blue noise Its power density increases 3 dB per octave with increasing frequency (density proportional to f ) over a finite frequency range.

5. Violet noise (purple noise) Its power density increases 6 dB per octave with increasing frequency (density proportional to f ²) over a finite frequency range. It is also known as differentiated white noise.

6. Grey noise It is obtained from white noise. Over a given range of audio frequencies the low and high frequencies are pre-amplified, in order to be perceived by the human ear to be equally loud at all frequencies.

7. Green noise It is supposed to be the background noise of the Universe. Its power spectrum is similar to that of the pink noise, with a spike added around 500 Hz. It can be generated by bounding the Brown(ian) noise.

8. Black noise It can be viewed as white noise with opposite signs, i.e. the noise that cancels out white noise (see definition a)). Two definitions are proposed:

   a) Silence, eventually with occasional random spikes.

   b) Noise with a 1/f ^β spectrum, where β > 2. Used to model some environmental processes. It is a characteristic of "natural and unnatural catastrophes like floods, droughts, bear markets, and various outrageous outages, such as those of electrical power." (Manfred Schroeder: Fractals, Chaos, Power Laws: Minutes from an Infinite Paradise. W. H. Freeman, New York, 1992. ISBN 978-0716723578).

9. Orange noise It is a quasi-stationary noise with a finite power spectrum. Its main characteristic is a finite number of small bands of zero energy dispersed throughout a continuous spectrum. Orange noise relates to musical scales.

• Conducted interference: It appears when the system unintentionally produces signals that are conducted away form itself. Generally, conducted interference travels along lines, cables and wires. (Penguin Dictionary of Electronics)

• Contact noise: Occurring in discontinuous conductors (as carbon resistors) which are fabricated by compressed particles. This noise adds to the thermal noise of the resistor and sometimes is called “excess noise”. Also associated to dirty mechanical contacts which ohmic resistance is fluctuating.

• Correlation: The correlation describes a relationship between two fluctuations quantities which have a natural tendency to influence one another (this tendency not just being a chance result). A cross-correlation appears when the considered fluctuations have at least one physical mechanism generating them in common. The auto-correlation function provides an indication of how fast a fluctuation evolve in time.

• Coupling: The interaction between two circuits consisting in the transfer of energy from one to the other.

• Crest factor (peak factor): The ratio of: (a) the peak value of a periodic signal to (b) its root-mean-square (rms) value.

• Crosstalk: Undesired energy (disturbance) appearing in a transmission path by mutual coupling with other transmission paths.

• Cyclostationary noise: Is a noise signal having statistical properties that vary cyclically with time. Circuits with time-varying operation points can generate cyclostationary noise. Cyclostationarity occurs when the time-varying operating point modulates the noise generated by bias-dependent noise sources or when the time-varying circuit modulates the transfer function from a constant noise source to the output. (Joel Phillips and Ken Kundert)

• Deep sub-micron noise: Any phenomenon that causes the voltage at a non switching node to deviate from its nominal value.

• Dithering: The application of a small perturbation or noise to a measurement to reduce the effect of small local non-linearities. (Penguin Dictionary of Electronics)

• Earth: A large conducting body, such as the earth, that is taken to be the arbitrary zero reference potential.

• Electrochemical noise: This noise refers to naturally occurring fluctuations in corrosion potential and corrosion current flow. Electrochemical noise estimation is used as a non-intrusive method for corrosion monitoring.

• Electromagnetic Compatibility (EMC): The capability of electronic systems, equipment or devices to operate in their intended electromagnetic environment without suffering or causing unacceptable degradation of performance as a result of electromagnetic interference.

• Electrostatic discharge (ESD): Is a phenomenon in which a burst of charge accumulated by friction is transferred to the system causing it to fail (typically, due to damage of the semiconductor devices). (Penguin Dictionary of Electronics)

• Electromagnetic immunity: A relative measure of a device or system capability to withstand EMI exposure while maintaining a predefined performance level.

• Electromagnetic Interference (EMI): EMI is the degradation of the performance of a device, circuit or system caused by an unwanted electromagnetic perturbation. This perturbation may be either the result of a process by which disruptive electromagnetic energy is transmitted from one electronic device to another via radiated or conducted paths (or both) or can be externally generated (for instance, sky noise).

• Electromagnetic susceptibility: A relative measure of a device or system inability to perform without degradation of performance in the presence of an electromagnetic perturbation. Lack of electromagnetic immunity.

• Electronic noise: It exists in all circuits and devices as a result of fluctuations in current or voltage caused by the random movement of charge carriers, random generation and recombination of carriers, manufacturing quality and semiconductor defects.

• Excess noise factor: There are multiple definitions and notations. Some of them are given below:

1. A factor, F, indicating the increase in shot noise in an avalanche photodiode (APD) as compared with an ideal (noiseless) multiplier.

2. The noise which results from variations in avalanche gains (is significant in detectors made of semiconductors with similar ionization coefficient values for electrons and holes, such as germanium and III-V compound photodiodes).

3. For amplification of a noisy signal, the excess noise factor is defined as the squared SNR degradation rate, from input to output of the detector:

   

4. In optoelectronics, the excess noise factor (denoted F) is preferred instead of the variance of the gain. Its definition is:

   

   with M being the APD gain and the variance of the avalanche electron gain. For more details see: Teich M.C., Matsuo K., Saleh B.E.A.: Excess Noise Factors for Conventional and Superlattice Avalanche Photodiodes and Photomultiplier Tubes. IEEE J. of Quantum Electronics, Vol. QE-22, no 8, 1986, pp 1186 – 1193. DOI 10.1109/JQE.1986.1073137

• Extrinsic noise: Is the noise generated outside the system of interest, which merely acts as a receiving antenna. For this reason, this kind of noise is also called extraneous signals, spurious signals, interfering signals or perturbations. Extrinsic noise sources can be grouped into two categories:

1. Natural noise sources:

• Atmospheric noise This noise has its origin in natural atmospheric phenomena, mainly lightning discharges and thunderstorms.

• Precipitation noise This noise is encountered in rain, snow, hail and dust storms located in the vicinity of the receiving antenna.

• Galactic noise (Sky noise) It is the noise at radio frequencies caused by disturbances that originate outside the Earth or its atmosphere (for instance noise of the Sun, Cassiopeia A, quasars, interstellar space, etc.)

2. Industrial noise sources:

• Electromagnetic noise sources Major sources belonging to this category are: high-power electric motors involved in transport systems (trains, underground, conveyor belts, elevators, etc.), arc welders, automotive ignition systems, high-voltage transmission lines, AC supply lines, fluorescent lamps, transmitters (mobile phones, cordless phones, radio, television, radars, Wi-Fi, etc.), ISM equipments (microwave owens, relay-controlled devices, laser cutter, computers, scanners, medical equipments, etc.) a.s.o.

• Electrostatic noise sources It relates to triboelectric effect (generation of electrical charges by friction of two dissimilar solids) and piezoelectric effect (generation of a potential difference in a crystal when a strain is introduced).

• Noise of non-electrical origin Under this label are grouped non-electric phenomena that generate voltage or current fluctuations, namely: galvanic action, electrochemical contamination (as the fluctuating voltage appearing between two tracks on the PCB separated by a contaminated insulating material), Seebeck effect, poor mechanical contacts, poor solder joints, a.s.o.

• Fixed-pattern (spatial) noise (FPN): It is the spatial variation in pixel output values under uniform illumination due to device and interconnect parameter variations (mismatches) across the sensor. It is fixed for a given sensor, but varies from sensor to sensor.

• Floating: Related to a circuit or device that is not connected to any source of potential.

• Fluctuations (in the field of electronics): The temporal irregular variations in macroscopic quantities (voltage, current, temperature, energy, etc.), usually around a mean-value. Thermal fluctuations are random deviations of a system from its equilibrium and they are an important source of noise. Two basic principles:

1. Whenever fluctuations in a macroscopic quantity are observed, they display the cumulative effect of numerous individual jumps of particle size (N.G. van Kampen).

2. In real life, the frequency of the fluctuation is related to the involved energy. Fast fluctuating processes involve a big amount of energy, while slow fluctuating processes involve little energy.

• Gasket: A flexible joint between two metallic enclosures which enables good electrical contact between them and prevent intrusion of electromagnetic waves.

• Genetic algorithm: An algorithm that imitates biological evolutionary processes intended to solve optimization problems.

• Ground: A conductive system whose potential is taken as reference for all voltages and currents in the circuit. Note that an electronic equipment may have several grounds and some of them may float.

• Heterojunction: A junction between dissimilar semiconductor materials.

• Impulse noise: Noise consisting of random occurrences of energy spikes having random amplitude, random spectral content and short duration.

• Inductive noise: Voltage transients that appear across an inductor when the current in it varies abruptly (as in switching circuits).

• Input noise: A pulse/glitch that appears at the inputs of dynamic gates and discharges the dynamic node.

• Interference:

1. Undesired signals (disturbances) within the useful frequency band produced by other services.

2. In telecommunications, the effect of disturbances which alter, modify, or disrupt a message as it travels along a channel between a source and a receiver. Typically the term refers to the addition of an unwanted signal to the useful signal.

• Intrinsic noise: Noise generated inside the investigated system, device or circuit. According to the involved physical mechanism, several categories of noise exist. The most important ones are:

1. Thermal noise It is caused by the thermal (Brownian) movement of charge carriers (electrons) in a piece of conductive material, under zero bias. Random temporary agglomeration of carriers to one end or the other occurs, hence a fluctuating voltage in time appears. Its mean value must be zero, since no DC voltage is applied.

2. Shot noise Two definitions have been proposed.

   1) The statistical fluctuation that arises in a signal which counts a number of discrete objects per time interval, e.g. electrons at low current intensities or photons in a light beam.

   2) In electronics, shot noise is caused by the random passage of electrons and holes through a potential barrier (without considering collision).

3. Diffusion noise It is due to the charge carrier velocity fluctuations caused by collisions. This is related to diffusion process that results from non-uniform carrier distribution (for instance, excess carriers generated by illuminating one end of a semiconductor).

4. Flicker noise (1/f noise) It is the result of random trapping and release of charge carriers in the bulk or surface of a semiconductor device.

5. Generation-Recombination noise (G-R noise) This noise is related to statistical fluctuations in the population of charge carriers, due to random generation, random recombination, random trapping and release of carriers in the bulk of a semiconductor.

6. Popcorn (burst) noise Equally called Random Telegraph Signal noise (RTS noise). It consists of sudden step-like transitions between two or more discrete voltage or current levels, at random and unpredictable times. The physical origin of this noise is not well understood, but it seems to be associated with shallow, heavily doped emitter junctions and poor quality devices. It is also present in sub-micron bipolar or MOS transistors with lattice structure damage in sensitive areas. The most invoked cause is the random trapping and release of charge carriers at thin film interfaces or at defect sites in bulk semiconductor.

7. Quantum noise The fundamental origin of quantum noise is related to the quantified (discrete) nature of electromagnetic radiation. A quantum noise signal is related to the temporary change in the amount of energy in a point in space, for instance due to fluctuations in the average rate of incidence of quanta on a detector. The basic electromagnetic quantum of noise power is just 1 photon per electromagnetic mode. (R. F. Graf: Modern Dictionary of Electronics)

8. Avalanche noise It refers to stochastic carrier multiplication due to impact ionization in reverse-biased junctions operating near breakdown. Micro-plasma regions appear in the affected area, and they are randomly distributed in space and randomly activated in time.

Remark Thermal and shot noise are unavoidable since due to the laws of nature rather than to the device exhibiting them. The remaining ones depend mostly on manufacturing quality and semiconductor defects.

• Jamming: Is a usually deliberate transmission of powerful signals to saturate a radio / TV receiver or a radar. The purpose is to disrupt communication or battle control.

• Jitter: Jitter is a time variation in the zero-crossing points of a signal, or a time variation in the period of the signal.

• Johnson noise: Thermal noise that occurs in resistors.

• Mesoscopic: It refers to a system or process where the typical length scale is of the order of nanometers and the energy scales comparable to thermal energy.

• Noise (definitions):

1. Unwanted disturbances superposed upon a useful signal that tend to obscure its information content. (IEEE Standard Dictionary of Electrical and Electronics Terms)

2. Irregular fluctuations accompanying a transmitted signal but not relevant to it. (Oxford English Reference Dictionary)

3. In digital circuits: any deviation of a signal from its nominal value in those subintervals of time when it should otherwise be stable.

4. In signal processing or computing: any unwanted data (or data without meaning). It refers to data that is not being used to transmit a signal, but is simply produced as an unwanted by-product of other activities.

• Noise bandwidth: The bandwidth Df of an ideal circuit (with rectangular power-transfer characteristics) such that the total transmitted noise power is equal to that transmitted by the actual circuit.

• Noise equivalent power (NEP): In optical (or thermal) detectors, it is the input signal power (light power) that produces an output electrical signal equal to the noise output present when no input is applied, per unit bandwidth.

• Noise floor (receiver sensitivity): The lower limit of the input signal available power (S_i) required to achieve the maximum output S/N ratio in normal operation.

• Noise immunity: The ability of a device, circuit or system to operate correctly when interference (noise) is present. Noise immunity is rated according to the noise intensity at which the disruption of the equipment’s functions is still within permissible limits. For instance, the immunity of a CMOS logic gate to noise signals is a function of many variables (individual chip differences, fan-in and fan-out, stray inductance and capacitance, supply voltage, location of the noise, shape of the noise signal, temperature, etc.). Moreover, the immunity of a system of gates usually differs from that of any individual gate. (Fairchild Semiconductor, AN-377)

• Noise index: This parameter is used to express the amount of excess noise in a physical resistor. It is defined in one decade of frequency as the ratio of: (a) the rms value (in mV) of the excess noise voltage, to (b) the DC drop across the resistor (in V).

• Noise margin: The maximum voltage amplitude of extraneous signal that can be algebraically added to the noise-free worst-case input level without causing the output voltage to deviate from the allowable logic voltage level. (JEDEC Dictionary). NOTE: the term "input" refers to logic input terminals, power supply terminals, or ground reference terminals.

• Pad: Attenuator.

• Phase noise: It is defined in the frequency domain as the representation of rapid, short-term, random fluctuations in the phase of a waveform, caused by time domain instabilities (jitter).

• Pigtail: The piece of electrical wire used to connect two or more wires or to connect the shield of a cable to ground.

• Power spectrum: A plot which shows how the amount of power in a signal is distributed across different frequencies. The power spectrum is calculated using the Fourier transform.

• Quantization noise: Resulting from the inaccurate representation of analogue signals in a digital system of limited resolution. (Penguin Dictionary of Electronics)

• Radiated interference: It appears when the system unintentionally produces signals that are radiated away form itself. Generally, radiated interference travels through the space between aggresor and victim. (Penguin Dictionary of Electronics)

• Salt and pepper noise: Is typically seen on images. It is related to randomly occurring white and black pixels. Salt and pepper noise appears into images in situations where quick transients take place.

• Shield: A conductive barrier separating sources from receptors, to reduce the effects of source electromagnetic fields coupling to receptors.

• Shielding effectiveness: An insertion loss measure of the ability of a shield to exclude or confine electromagnetic waves, usually expressed in the frequency domain as a ratio of the incident to penetrating signal amplitudes, in decibels.

• Signal Integrity (SI): Any signal waveform deviation form its ideal shape. Hence, it  is a measure of the quality of a signal. It relates to various factors that affect both the performance and reliability of high-speed digital systems. For instance: signal reflections, attenuation, ringing, crosstalk, jitter, unwanted ground currents, timing errors, ground bounce, electromagnetic radiation, power-supply noise, etc.

• Signal to noise ratio (SNR): At a specified frequency, it is the ratio of the value of the signal to that of the noise, both being expressed in a consistent way (as for example peak signal to peak noise ratio, rms signal to rms noise ratio, peak-to-peak signal to peak-to-peak noise ratio, etc.). (IEEE Standard Dictionary of Electrical and Electronics Terms)

• Simultaneous switching noise (SSN, equally called Ground Bounce or Delta-I noise): This refers to a voltage spike generated in a digital system by the simultaneous switching of many circuits, due to fast-changing currents across the parasitic inductance of V_DD and ground lines of integrated circuits.

• Speckle noise: This noise has its origin in the interference of many waves of the same frequency, having different phases and amplitudes, which result in a medium containing many sub-resolution scatterers. As a result, a random, deterministic, interference pattern appears and affects a detected image.The speckle effect is observed when radio waves are scattered from rough surfaces such as ground or sea, but it can also be observed in ultrasonic imaging.This kind of noise is present in both RF data and envelope-detected data. For instance, speckle noise is a granular noise that inherently exists in and degrades the quality of the active radar and synthetic aperture radar (SAR) images. In conventional radar, it results from random fluctuations in the return signal from an object that is smaller than a single image-processing element. It increases the mean grey level of a local area. In SAR, speckle noise is a multiplicative noise (causing difficulties for image interpretation). (Wikipedia) See also: http://dukemil.bme.duke.edu/Ultrasound/k-space/node5.html

• Spectral density: Power distribution in the frequency spectrum.

• Static noise: Any deviation from the nominal supply or ground voltages at evaluation nodes which should otherwise represent stable logic “one” or “zero”.

• Substrate noise: In an integrated circuit, a signal can couple from one node to another via the substrate. This phenomenon is referred to as substrate noise coupling or substrate noise.

• Temporal noise: In optoelectronics, it refers to the time-dependent fluctuations that are of fundamental origin, unlike fixed-pattern noise. Comments:

1. Note that in the proposed definition, “time-dependent fluctuations” does not refer to their amplitude (which of course is time dependent!) but rather to the fact that their characteristics are related to the continual modification of MOS transistor quiescent point.

2. Circuit-oriented temporal noise originating from substrate coupling or poor power-supply rejection is not included.

• Video noise: This term refers to the random dot pattern that is superimposed on the picture as a result of electronic noise, the “snow” that is seen with poor (analog) television reception or on VHS tapes. Interference is another form of noise, in the sense that it is unwanted, though not random, and can affect radio and television signals.

• Visual noise: Is the noise present in images. Electronic noise will be present in camera sensors, and the physical size of the grains of film emulsion creates visual noise. This kind of noise is referred to as "grain." Noise is also used in the creation of 2D and 3D images by computer. Sometimes noise is added to images to hide the sudden transitions inherent in digital representation of color, known as "banding". This adding of noise is referred to as "dithering."

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