Transcription
“Book/Definitions”Electrical Engineering Dictionary.Ed. Phillip A. LaplanteBoca Raton: CRC Press LLC, 2000
SpecialSymbolsα-level seta crisp set of elements belonging to a fuzzy set A at least to a degree αAα {x X µA (x) α}See also crisp set, fuzzy set.1fhertz.common symbol for bandwidth, incommon symbol for gallium ar rGaAssenide relative dielectric constant. rGaAs 12.8.common symbol for silicon relative rSidielectric constant. rSi 11.8. 0symbol for permitivity of free space. 0 8.849 10 12 farad/meter.common symbol for relative dielectric rconstant.common symbol for DC to RF conηDCversion efficiency. Expressed as a percentage.common symbol for power added efηaficiency. Expressed as a percentage.common symbol for total or true effiηtciency. Expressed as a percentage.common symbol for source reflec0opttion coefficient for optimum noise performance.c2000 by CRC Press LLCµ0common symbol for permeability offree space constant. µ0 1.257 10 16henrys/meter.common symbol for relative permeµrability.ωcommon symbol for radian frequencyin radians/second. ω 2 · π · frequency.common symbol for positive transitionθ angle in degrees.common symbol for negative transiθ tion angle in degrees.common symbol for conduction anθcondgle in degrees.common symbol for saturation angleθsatin degrees.common symbol for FET channelθCCto-case thermal resistance in C/watt.common symbol for bipolar junctionθJ Cto-case thermal resistance in C/watt.common symbol for Richardson’sA constant. A 8.7 amperes · cm/ KBVGDvoltage.See gate-to-drain breakdownBVGSvoltage.See gate-to-source breakdowndv/dtrate of change of voltage withstand capability without spurious turn-on ofthe device.HciSee intrinsic coercive force.common symbol for excess noise innewatts.ns hwatts.common symbol for shot noise in
ntcommon symbol for thermal noise inwatts.deux indices,” IRIA Rapport Laboria, No.31, Sept. 1973.10base2a type of coaxial cable used toconnect nodes on an Ethernet network. The10 refers to the transfer rate used on standardEthernet, 10 megabits per second. The basemeans that the network uses baseband communication rather than broadband communications, and the 2 stands for the maximumlength of cable segment, 185 meters (almost200). This type of cable is also called “thin”Ethernet, because it is a smaller diameter cable than the 10base5 cables.2-D Fornasini–Marchesini modelmodel described by the equations10base5a type of coaxial cable used toconnect nodes on an Ethernet network. The10 refers to the transfer rate used on standard Ethernet, 10 megabits per second. Thebase means that the network uses basebandcommunication rather than broadband communications, and the 5 stands for the maximum length of cable segment of approximately 500 meters. This type of cable is alsocalled “thick” Ethernet, because it is a largerdiameter cable than the 10base2 cables.10baseTa type of coaxial cable used toconnect nodes on an Ethernet network. The10 refers to the transfer rate used on standardEthernet, 10 megabits per second. The basemeans that the network uses baseband communication rather than broadband communications, and the T stands for twisted (wire)cable.2-D Attasi modelby the equationsa 2-D model describedxi 1,j 1 A1 A2 xi,j A1 xi 1,j A2 xi,j 1 Buijyij Cxij Duiji, j Z (the set of nonnegative integers).Here xij R n is the local state vector,uij R m is the input vector, yij R p isthe output vector, and A1 , A2 , B, C, D arereal matrices. The model was introduced byAttasi in “Systemes lineaires homogenes ac2000 by CRC Press LLCa 2-Dxi 1,j 1 A0 xi,j A1 xi 1,j A2 xi,j 1 Buij (1a)(1b)yij Cxij Duiji, j Z (the set of nonnegative integers)here xij R n is the local state vector,uij R m is the input vector, yij R p isthe output vector Ak (k 0, 1, 2), B, C, Dare real matrices. A 2-D model described bythe equationsxi 1,j 1 A1 xi 1,j A2 xi,j 1 B1 ui 1,j B2 ui,j 1 (2)i, j Z and (1b) is called the second 2-DFornasini–Marchesini model, where xij , uij ,and yij are defined in the same way as for (1),Ak , Bk (k 0, 1, 2) are real matrices. Themodel (1) is a particular case of (2).2-D general modela 2-D model described by the equationsxi 1,j 1 A0 xi,j A1 xi 1,j A2 xi,j 1 B0 uij B1 ui 1,j B2 ui,j 1yij Cxij Duiji, j Z (the set of nonnegative integers)here xij R n is the local state vector, uij R m is the input vector, yij R p is the outputvector and Ak , Bk (k 0, 1, 2), C, D are realmatrices. In particular case for B1 B2 0we obtain the first 2-D Fornasini–Marchesinimodel and for A0 0 and B0 0 we obtainthe second 2-D Fornasini–Marchesini model.2-D polynomial matrix equationequation of the formAX BY Ca 2-D(1)where A R k p [s], B R k q [s], C R k m [s] are given, by a solution to (1) we
mean any pair X R p m [s], Y R q m [s]satisfying the equation. The equation (1)has a solution if and only if the matrices[A, B, C] and [A, B, 0] are column equivalent or the greatest common left divisor of Aand B is a left divisor of C. The 2-D equationAX Y B CR k pR q m [s],(2)are equivalent.2-D Roesser modela 2-D model described by the equations# " " h # hxi 1,jxijA1 A2B1 uvA3 A4B2 ijxi,j 1xijvi, j Z (the set of nonnegative integers)," #xhyij C ijv DuijxijHere xijh R n1 and xijv R n2 are the horizontal and vertical local state vectors, respectively, uij R m is the input vector, yij R pis the output vector and A1 , A2 , A3 , A4 , B1 ,B2 , C, D are real matrices. The model wasintroduced by R.P. Roesser in “A discretestate-space model for linear image processing,” IEEE Trans. Autom. Contr., AC-20,No. 1, 1975, pp. 1-10.2-D shuffle algorithm an extension of theLuenberger shuffle algorithm for 1-D case.The 2-D shuffle algorithm can be used forchecking the regularity conditiondet [Ez1 z2 A0 A1 z1 A2 z2 ] 6 0for some (z1 , z2 ) C C of the singular general model ( See singular 2-D general model).2000 by CRC Press LLC2-D Z-transformF (z1 , z2 ) of a discrete 2-D function fij satisfying the condition fij 0 for i 0 or/and j 0 isdefined byF (z1 , z2 ) R k m [s]C A [s], B are given, is called the bilateral 2-D polynomial matrix equation. By a solution to (2) wemean any pair X R p m [s], Y R k q [s]satisfying the equation. The equation has asolution if and only if the matrices A 0ACand0 B0 BcThe algorithm is based on the row compression of suitable matrices. XX jfij z1 i z2i 0 j 0An 2-D discrete fij has the 2-D Z-transformif the sum XX jfij z1 i z2i 0 j 0exists.2DEGFETSee high electron mobilitytransistor(HEMT).2LGSee double phase ground fault.3-dB bandwidthfor a causal low-passor bandpass filter with a frequency functionH (j ω) the frequency at which H (j ω) dBis less than 3 dB down from the peak value H (ωP ) .3-level lasera laser in which the mostimportant transitions involve only three energy states; usually refers to a laser in whichthe lower level of the laser transition is separated from the ground state by much less thanthe thermal energy kT. Contrast with 4-levellaser.3-level systema quantum mechanicalsystem whose interaction with one or moreelectromagnetic fields can be described byconsidering primarily three energy levels.For example, the cascade, vee, and lambdasystems are 3-level systems.4-level lasera laser in which the mostimportant transitions involve only four energy states; usually refers to a laser in whichthe lower level of the laser transition is separated from the ground state by much more
than the thermal energy kT . Contrast with3-level laser.45 Mbs DPCM for NTSC color videoa codec wherein a subjectively pleasing picture is required at the receiver. This doesnot require transparent coding quality typicalof TV signals. The output bit-rate for videomatches the DS3 44.736 Megabits per secondrate. The coding is done by PCM coding theNTSC composite video signal at three timesthe color subcarrier frequency using 8 bit perpixel. Prediction of current pixel is obtainedby averaging the pixel three after current and681 pixels before next to maintain the subcarrier phase. A leak factor is chosen beforecomputing prediction error to main the quali-c2000 by CRC Press LLCty of the image. For example a leak factor of3132 the prediction decay is maintained at thecenter of the dynamic range.XL 128 31 X 128 .32Finally, a clipper at the coder and decoderis employed to prevent quantization errors.90% withstand voltagea measure ofthe practical lightning or switching-surge impulse withstand capability of a piece of powerequipment. This voltage withstand level istwo standard deviations above the BIL of theequipment.
Aa posteriori probabilitystatistics.a priori probabilitySee posteriorSee prior statistics.A-mode displayreturned ultrasoundechoes displayed as amplitude versus depthinto the body.A-sitein a ferroelectric material with thechemical formula ABO3 , the crystalline location of the A atom.A/DSee analog-to-digital converter.AALSee ATM adaptation layer.ABCSee absorbing boundary condition.ABCDpropagation of an optical raythrough a system can be described by a simple 2 2 matrix. In ray optics, the characteristic of a system is given by the corresponding ray matrix relating the ray’s position fromthe axis and slope at the input to those at theoutput.ABCD formalismanalytic method usingtwo-by-two ABCD matrices for propagatingGaussian beams and light rays in a wide variety of optical systems.ABCD lawanalytic formula for transforming a Gaussian beam parameter fromone reference plane to another in paraxial optics, sometimes called the Kogelnik transformation. ABCD refers to the ABCD matrix.ABCD matrixthe matrix containingABCD parameters. See ABCD parameters.ABCD parametersa convenient mathematical form that can be used to characterizec2000 by CRC Press LLCtwo-port networks. Sometimes referred toas chain parameters. ABCD parameters arewidely used to model cascaded connectionsof two-port microwave networks, in whichcase the ABCD matrix is defined for eachtwo-port network. ABCD parameters canalso be used in analytic formalisms for propagating Gaussian beams and light rays. Raymatrices and beam matrices are similar butare often regarded as distinct.ABC parameters have a particularly useful property in circuit analysis where thecomposite ABCD parameters of two cascaded networks are the matrix products ofthe ABCD parameters of the two individualcircuits. ABCD parameters are defined as ABv2v1 i1i2CDwhere v1 and v2 are the voltages on ports oneand two, and i1 and i2 are the branch currentsinto ports one and two.aberrationan imperfection of an opticalsystem that leads to a blurred or a distortedimage.abnormal event any external or programgenerated event that makes further normalprogram execution impossible or undesirable, resulting in a system interrupt. Examples of abnormal events include system detection of power failure; attempt to divide by0; attempt to execute privileged instructionwithout privileged status; memory parity error.abort(1) in computer systems, to terminate the attempt to complete the transaction,usually because there is a deadlock or because completing the transaction would result in a system state that is not compatible with “correct” behavior, as defined by aconsistency model, such as sequential consistency.(2) in an accelerator, terminating the acceleration process prematurely, either by inhibiting the injection mechanism or by removing circulating beam to some sort of
dump. This is generally done to prevent injury to some personnel or damage to accelerator components.ABRSee available bit rate.absolute addressan address within aninstruction that directly indicates a location inthe program’s address space. Compare withrelative addressing.absolute addressingan addressing modewhere the address of the instruction operandin memory is a part of the instruction so thatno calculation of an effective address by theCPU is necessary.For example, in the Motorola M68000 architecture instruction ADD 5000,D1, a 16-bitword operand, stored in memory at the wordaddress 5000, is added to the lower word inregister D1. The address “5000” is an example of using the absolute addressing mode.See also addressing mode.absolute encoderan optical devicemounted to the shaft of a motor consistingof a disc with a pattern and light sources anddetectors. The combination of light detectorsreceiving light depends on the position of therotor and the pattern employed (typically theGray code). Thus, absolute position information is obtained. The higher the resolutionrequired, the larger the number of detectorsneeded. See also encoder.absolute moment The pth order absolutemoment µp of a random variable X is theexpectation of the absolute value of X raisedto the pth power:µp E[ X ]p .See also central moment, central absolutemoment. See also expectation.absolute pressureunits to measure gaspressure in a vacuum chamber with zero being a perfect vacuum. Normally referred toas psia (pounds per square inch absolute).c2000 by CRC Press LLCabsolute sensitivitydenoted S(y, x), issimply the partial derivative of y with respectto x, i.e., S(y, x) y/ x, and is used toestablish the relationships between absolutechanges. See sensitivity, sensitivity measure,relative sensitivity, semi-relative sensitivity.absolute stabilityoccurs when the network function H (s) has only left half-planepoles.absorbergeneric term used to describematerial used to absorb electromagnetic energy.Generally made of polyurethanefoam and impregnated with carbon (and fireretardant salts), it is most frequently used toline the walls, floors and ceilings of anechoicchambers to reduce or eliminate reflectionsfrom these surfaces.absorbing boundary condition (ABC)afictitious boundary introduced in differentialequation methods to truncate the computational space at a finite distance without, inprinciple, creating any reflections.absorption(1) process that dissipates energy and causes a decrease in the amplitudeand intensity of a propagating wave betweenan input and output reference plane.(2) reduction in the number of photons of aspecific wavelength or energy incident upona material. Energy transferred to the materialmay result in a change in the electronic structure, or in the relative movement of atoms inthe material (vibration or rotation).(3) process by which atoms or moleculesstick to a surface. If a bond is formed, it istermed chemisorption, while the normal caseis physisorption. The absorption process proceeds due to, and is supported by, the fact thatthis is a lower energy state.absorption coefficient (1) in a passive device, the negative ratio of the power absorbed(pabsorbed pin pout ) ratioed to the power in(pin pincident preflected ) per unit length (l),usually expressed in units of 1/wavelength or1/meter.
(2) factor describing the fractional attenuation of light with distance traversed in amedium, generally expressed as an exponential factor, such as k in the function e kx ,with units of (length)-1. Also called attenuation coefficient.absorption cross sectionenergy absorbed by the scattering medium, normalized to the wavenumber. It has dimensionsof area.absorption edgethe optical wavelengthor photon energy corresponding to the separation of valence and conduction bands insolids; at shorter wavelengths, or higher photon energies than the absorption edge, the absorption increases strongly.absorption grating(1) a diffractiongrating where alternate grating periods areopaque.(2) an optical grating characterized byspatially periodic variation in the absorptionof light. Absorption gratings are generallyless efficient than phase gratings.absorption optical fiberthe amount ofoptical power in an optical fiber capturedby defect and impurity centers in the energybandgap of the fiber material and lost in theform of longwave infrared radiation.ACSee alternating current.AC bridgeone of a wide group ofbridge circuits used for measurements of resistances, inductances, and capacitances, andto provide AC signal in the bridge transducersincluding resistors, inductors, and capacitors.The Wheatstone bridge can be used witha sinusoidal power supply, and with an ACdetector (headphones, oscilloscope), one canuse essentially the same procedure for measurement of resistors as in DC applications.Only a small number of other AC bridges areused in modern electric and electronic equipment. A strong selection factor was the factthat in a standard capacitor the electrical pa-c2000 by CRC Press LLCrameter are closest to the parameters of anideal capacitor. Hence, not only a capacitance is measured in terms of capacitance (inresistive ratio arms bridges), but the inductance as well is measured in terms of capacitance (Hay and Owen bridges).The AC bridges with ratio arms that aretightly coupled inductances allow measurement of a very small difference between currents in these inductances, and this fact isused in very sensitive capacitance transducers.AC circuit electrical network in which thevoltage polarity and directions of current flowchange continuously, and often periodically.Thus, such networks contain alternating currents as opposed to direct currents, therebygiving rise to the term.AC couplinga method of connecting twocircuits that allows displacement current toflow while preventing conductive currents.Reactive impedance devices (e.g., capacitorsand inductive transformers) are used to provide continuity of alternating current flowbetween two circuits while simultaneouslyblocking the flow of direct current.AC motoran electromechanical system that converts alternating current electrical power into mechanical power.AC plasma displaya display that employs an internal capacitive dielectric layerto limit the gas discharge current.AC steady-state powerthe averagepower delivered by a sinusoidal source to anetwork, expressed asP V · I cos(θ ) where 2· V and 2· I are the peakvalues, respectively, of the AC steady-statevoltage and current at the terminals. θ represents the phase angle by which the voltageleads the current.
AC/AC convertera power electronicsdevice in which an AC input voltage of somemagnitude, frequency, and number of phasesis changed to an AC output with changes toany of the previously mentioned parameters.AC/AC converters usually rectify the inputsource to a DC voltage and then invert theDC voltage to the desired AC voltage.ation error to a constraint on the gain of theopen loop system. The relevant equationsare ea K1a and Ka lims inf ty s 2 q(s),where q(s) is the transfer function modelof the open loop system, including the controller and the process in cascade, and s isthe Laplace variable. See also position errorconstant, velocity error constant.AC/DC converteraccelerator(1) a positive electrode in avacuum tube to accelerate emitted electronsfrom its cathode by coulomb force in a desired direction.(2) a machine used to impart large kineticenergies to charged particles such as electrons, protons, and atomic nuclei. The accelerated particles are used to probe nuclearor subnuclear phenomena in industrial andmedical applications.See rectifier.AC-DC integrated systema power system containing both AC and DC transmissionlines.ACARSaircraft communications addressing and reporting. A digital communications link using the VHF spectrum fortwo-way transmission of data between an aircraft and ground. It is used primarily in civilaviation applications.ACCSee automatic chroma control.accelerated testingtests conducted athigher stress levels than normal operation butin a shorter period of time for the specificpurpose to induce failure faster.accelerating powerthe excess electricpower at a synchronous machine unit whichcannot be transmitted to the load because ofa short circuit near its terminals. This energygives rise to increasing rotor angle.acceleration errorthe final steady difference between a parabolic setpoint and theprocess output in a unity feedback controlsystem. Thus it is the asymptotic error in position that arises in a closed loop system thatis commanded to move with constant acceleration. See also position error, velocity error.acceleration error constanta gain Kafrom which acceleration error ea is readily determined. The acceleration error constant is a concept that is useful in the designof unity feedback control systems, since ittransforms a constraint on the final acceler-c2000 by CRC Press LLCacceptable delaythe voice signal delay that results in inconvenience in the voicecommunication. A typically quoted value is300 ms.acceptancein an accelerator, it defineshow "large" a beam will fit without scraping into the limiting aperture of a transportline. The acceptance is the phase-space volume within which the beam must lie to betransmitted through an optical system without losses. From an experimenters pointof view acceptance is the phase-space volume intercepted by an experimenter’s detector system.acceptor(1) an impurity in a semiconductor that donates a free hole to the valenceband.(2) a dopant species that traps electrons,especially with regard to semiconductors.access channela channel in a communications network that is typically allocated forthe purpose of setting up calls or communication sessions. Typically the users share theaccess channel using some multiple accessalgorithm such as ALOHA or CSMA.
access controla means of allowing access to an object based on the type of access sought, the accessor’s privileges, and theowner’s policy.access control lista list of items associated with a file or other object; the list contains the identities of users that are permittedaccess to the associated file. There is information (usually in the form of a set of bits)about the types of access (such as read, write,or delete) permitted to the user.access control matrixa tabular representation of the modes of access permittedfrom active entities (programs or processes)to passive entities (objects, files, or devices).A typical format associates a row with an active entity or subject and a column with anobject; the modes of access permitted fromthat active entity to the associated passive entity are listed in the table entry.access linea communication line thatconnects a user’s terminal equipment to aswitching node.access mechanisma circuit board or anintegrated chip that allows a given part of acomputer system to access another part. Thisis typically performed by using a specific access protocol.access protocola set of rules that establishes communication among different parts.These can involve both hardware and software specifications.access rightpermission to perform anoperation on an object, usually specified asthe type of operation that is permitted, suchas read, write, or delete. Access rights canbe included in access control lists, capabilitylists, or in an overall access control matrix.access timethe total time needed to retrieve data from memory. For a disk drivethis is the sum of the time to position theread/write head over the desired track and thec2000 by CRC Press LLCtime until the desired data rotates under thehead. (LW)accidental ratethe rate of false coincidences in the electronic counter experimentproduced by products of the reactions of morethan one beam particle within the time resolution of the apparatus.accumulation(1) an increase in the majority carrier concentration of a region ofsemiconductor due to an externally appliedelectric field.accumulator(1) a register in the CPU(processor) that stores one of the operandsprior to the execution of an operation, andinto which the result of the operation isstored. An accumulator serves as an implicitsource and destination of many of the processor instructions. For example, register Aof the Intel 8085 is an accumulator. See alsoCPU .(2) the storage ring in which successivepulses of particles are collected to create aparticle beam of reasonable intensity for colliding beams.achievable rate regionfor a multipleterminal communications system, a set ofrate-vectors for which there exist codes suchthat the probability of making a decoding error can be made arbitrarily small. See alsocapacity region, multiple access channel.achromatic the quality of a transport lineor optical system where particle momentumhas no effect on its trajectory through the system. In an achromatic device or system, theoutput beam displacement or divergence (orboth) is independent of the input beam’s momentum. If a system of lenses is achromatic,all particles of the same momentum will haveequal path lengths through the system.ACISee adjacent channel interference.
acknowledge(1) a signal which indicatesthat some operation, such as a data transfer,has successfully been completed.(2) to detect the successful completion ofan operation and produce a signal indicatingthe success.acoustic attenuationthe degree of amplitude suppression suffered by the acoustic wave traveling along the acousto-opticmedium.acoustic lasera laser (or maser) in whichthe amplified field consists of soundwaves orphonons rather than electromagnetic waves;phonon laser or phaser.acoustic memorya form of circulatingmemory in which information is encoded inacoustic waves, typically propagated througha trough of mercury. Now obsolete.acoustic velocitythe velocity of theacoustic signal traveling along the acoustooptic medium.acoustic wavea propagating periodicpressure wave with amplitude representingeither longitudinal or shear particle displacement within the wave medium; shear wavesare prohibited in gaseous and liquid media.acousto-optic cella device consisting ofa photo-elastic medium in which a propagating acoustic wave causes refractive-indexchanges, proportional to acoustic wave amplitude, that act as a phase grating for diffraction of light. See also Bragg cell.acousto-optic channelized radiometerSee acousto-optic instantaneous spectrumanalyzer in Bragg mode.acousto-optic correlatoran optical system that consists of at least one acoustooptic cell, imaging optics between cells andfixed masks, and photodetectors whose outputs correspond to the correlation function ofthe acoustic wave signal within one cell withc2000 by CRC Press LLCanother signal in a second cell, or with fixedsignals on a mask.acousto-optic deflector devicedevicewhere acousto-optic interaction deflects theincident beam linearly as a function of theinput frequency of the RF signal driving thedevice.acousto-optic devicedescriptor ofacousto-optic cells of any design; generallydescribes a cell plus its transducer structure(s), and may encompass either bulk,guided-wave, or fiber-optic devices.acousto-optic effectthe interaction oflight with sound waves and in particular themodification of the properties of a light waveby its interactions with an electrically controllable sound wave. See also Brillouinscattering.acousto-optic frequency excisorsimilarto an acousto-optic spectrum analyzer wherethe RF temporal spectrum is spatially and selectively blocked to filter the RF signal feeding the Bragg cell.acousto-optic instantaneous spectrum analyzer in Bragg mode device in which thetemporal spectrum of a radio frequency signal is instantaneously and spatially resolvedin the optical domain using a Fourier transform lens and a RF signal-fed Bragg cell.acousto-optic modulatora device thatmodifies the amplitude or phase of a lightwave by means of the acousto-optic effect.acousto-optic processoran optical system that incorporates acousto-optic cells configured to perform any of a number of mathematical functions such as Fourier transform, ambiguity transforms, and other timefrequency transforms.acousto-optic scannera device that usesan acoustic wave in a photoelastic medium
to deflect light to different angular positionsbased on the frequency of the acoustic wave.acousto-optic space integrating convolverdevice that is the same as an acousto-opticspace integrating convolver except that it implements the convolution operation.acousto-optic space integrating correlatoran acousto-optic implementation of the correlation function where two RF signals arespatially impressed on two diffracted beamsfrom Bragg cells, and a Fourier transformlens spatially integrates these beams onto apoint sensor that generates a photo currentrepresenting the correlation function.acousto-optic spectrum analyzeranacousto-optic processor that produces at aphotodetector output array the Fourier decomposition of the electrical drive signal ofan acousto-optic device.acousto-optic time integrating convolversame as the acousto-optic time integratingcorrelator, except implements the signal convolution operation. See acousto-optic timeintegrating correlator.acousto-optic time integrating correlatoran acousto-optic implementation of the correlation function where two RF signals arespatially impressed on two diffracted beamsfrom Bragg cells, and a time integrating sensor generates the spatially distributed correlation results.acousto-optic triple product processorsignal processor that implements a triple integration operation using generally both spaceand time dimensions.acousto-optic tunable filter (AOTF)anacousto-optic device that selects specific optical frequencies from a broadband opticalbeam, depending on the number and frequencies of acoustic waves generated in the device.c2000 by CRC Press LLCacousto-opticsthe area of study of interaction of light and sound in media, andits utilization in applications such as signalprocessing and filtering.ACPSee adjacent channel power.acquisition(1) in digital communications systems, the process of acquiring synchronism with the received signal. Thereare several levels of acquisitions, and for agiven communication system several of themhave to be performed in the process of settingup a communication link: frequency, phase,spreading code, symbol, frame, etc.(2) in analog communications systems,the process of initially estimating signal parameters (for example carrier frequency off
Special Symbols -level set a crisp set of elements belong-ing to a fuzzy set Aat least to a degree A Dfx2 Xj A.x/ g See also crisp set, fuzzy set. 1f common symbol for bandwidth, in hertz. rGaAs common sy
