Refimprove date August 2008 Modulation techniques Amplitude and Phase shiftkeying or Asymmetric Phase shiftkeying , APSK , is a digital modulation scheme that conveys Data Uses of data in computing data by changing, or modulating, both the amplitude and the Phase waves phase of a reference Signal information theory signal the carrier wave . In other words, it combines both Amplitudeshiftkeying ASK and Phase shiftkeying PSK to increase the Symbol data symbol set . It can be considered as a superclass of Quadrature amplitude modulation QAM . The advantage over conventional QAM, for example 16 QAM, is lower number of possible amplitude levels, resulting in fewer problems with non linear amplifiers. Applications The DVB S2 specification permits the use of 16APSK and 32APSK modes, allowing 16 and 32 different symbols respectively and are intended for mainly professional, semi linear applications. They can be also used for broadcasting but they require a higher level of available Carrier to noise ratio C N and an adoption of advanced Predistortion pre distortion methods in the uplink station in order to minimize the effect of transponder non linearity. Image with unknown copyright status removed Image M APSK.PNG Figure Bit mapping into constellations see Ref.2 References http www.ebu.ch en technical trev trev 300 morello.pdf DVB S2 ready for lift off , article in the European Broadcasting Union EBU technical review http public.ccsds.org publications archive 131x2o1.pdf Flexible Serially Concatenated Convolutional Turbo Codes with Near Shannon bound performance for telemtery applications , CCSDS 131.2 O 1. Category Quantized radio modulation modes electronics stub ca Modulaci per despla ament d amplitud i fase de Amplituden und Phasenmodulation es Modulaci n por desplazamiento de amplitud y fase ... more details
Modulation techniques Amplitudeshiftkeying ASK is a form of modulation that represents digital data as variations in the amplitude of a carrier wave . Any digital modulation scheme uses a wiktionary finite finite number of distinct signals to represent digital data. ASK uses a finite number of amplitudes, each assigned a unique pattern of bit binary digit s. Usually, each amplitude encodes an equal number of bits. Each pattern of bits forms the Symbol data symbol that is represented by the particular amplitude. The demodulator , which is designed specifically for the symbol set used by the modulator, determines the amplitude of the received signal and maps it back to the symbol it represents, thus recovering the original data. Frequency and Phase waves phase of the carrier are kept constant. Like Amplitude modulation AM , ASK is also linear and sensitive to atmospheric noise, distortions ... encoding schemes have been developed which represent data in groups using additional amplitude levels. For instance, a four level encoding scheme can represent two bit s with each shift in amplitude an eight level scheme can represent three bits and so on. These forms of amplitudeshiftkeying ... the Sensitivity of an AmplitudeShiftKeying ASK Receiver DEFAULTSORT AmplitudeShiftKeying ... es Modulaci n por desplazamiento de amplitud ko it Amplitudeshiftkeying kk ja pl ASK pt Modula o por chaveamento de amplitude ru ... Frequency shiftkeying Phase shiftkeying Nyquist ISI criterion Intersymbol interference Unreferenced ... to emit a low light level. This low level represents binary 0, while a higher amplitude lightwave ... a binary zero. This type of modulation is called on off keying , and is used at radio frequency ... a different carrier wave is sent with the relative amplitude. Out of the transmitter, the signal s t can ... we can easily understand that the probability to make an error decreases if the maximum amplitude of the transmitted ... more details
. References Reflist See also Amplitudeshiftkeying ASK Continuous phase frequency shiftkeying ... shiftkeying AFSK is a modulation technique by which digital data is represented by changes in the frequency ... zero. AFSK differs from regular frequency shiftkeying in performing the modulation at baseband frequencies ... shiftkeying to send and receive data, up to rates of about 1200 bits per second. The common Bell ... frequencies Frequency change signaling Multiple frequency shiftkeying MFSK Orthogonal frequency division multiplexing OFDM Phase shiftkeying PSK Federal Standard 1037C MIL STD 188 External links http cn.ece.cornell.edu publications papers icc2004 pp.pdf dFSK Distributed Frequency ShiftKeying Modulation ... shiftkeying mk nl Frequentieverschuivingsmodulatie ja pl Frequency ShiftKeying pt FSK ru fi FSK zh ... frequency RF Carrier wave carrier using a conventional technique, such as Amplitude modulation AM ... more details
ly represented data Amplitudeshiftkeying ASK Frequency shiftkeying FSK Phase shiftkeying PSK ...Modulation techniques Phase shiftkeying PSK is a digital modulation scheme that conveys Data Uses of data ... successive phases, it is termed differential phase shiftkeying DPSK . DPSK can be significantly simpler ... information &mdash Differential encoding differential schemes, Phase shiftkeying Differential phase shiftkeying .28DPSK.29 some of which do not need a reference carrier to a certain extent . A convenient ... and sine waves. Two common examples are binary phase shiftkeying Phase shiftkeying Binary phase shiftkeying BPSK BPSK which uses two phases, and quadrature phase shiftkeying Phase shiftkeying Quadrature phase shiftkeying QPSK QPSK which uses four phases, although any number of phases may .... Bluetooth 1 modulates with Minimum shiftkeying Gaussian minimum shiftkeying , a binary scheme ... 8 PSK modulation. Binary phase shiftkeying BPSK Image BPSK Gray Coded.svg 200px right thumb Constellation ... is the simplest form of phase shiftkeying PSK . It uses two phases which are separated by 180 and so ... the symbol error rate. Quadrature phase shiftkeying QPSK Image QPSK Gray Coded.svg 200px right ... zero, because only one bit of the symbol is changed at a time Offset quadrature phase shiftkeying OQPSK is a variant of phase shiftkeying modulation using 4 different values of the phase to transmit. It is sometimes called Staggered quadrature phase shiftkeying SQPSK . Image Oqpsk phase plot.svg ... signal ternary symbols . DPQPSK Dual polarization quadrature phase shiftkeying DPQPSK or dual polarization ... with application of the union bound to the signal constellation. Differential phase shiftkeying DPSK Differential encoding main differential coding Differential phase shiftkeying DPSK is a common ... variant of DPSK is Symmetric Differential Phase Shiftkeying, SDPSK, where encoding would be 90 ... the data as described above. Symmetric Differential Quadrature Phase ShiftKeying SDQPSK is like DQPSK ... more details
changes continuously and linearly. Gaussian minimum shiftkeying In digital communication , Gaussian minimum shiftkeying or GMSK is a continuous phase frequency shiftkeying modulation modulation scheme . It is similar to standard minimum shiftkeying MSK however the digital data stream ... Pasupathy, Minimum ShiftKeying A Spectrally Efficient Modulation , IEEE Communications Magazine ... & illustrations Aerospace Reflist Category Quantized radio modulation modes de Minimum ShiftKeying pl MSK es GMSK fr Gaussian minimum shiftkeying ja ru fi GMSK zh it Minimum shiftKeying ... more details
mergeinto Frequency shiftkeying date December 2011 Gaussian Frequency ShiftKeying GFSK is a type of Frequency ShiftKeying modulation that uses a Gaussian filter to smooth positive negative frequency deviations, which represent a binary 1 or 0. It is used by DECT , Bluetooth ref Sweeney, D. An introduction to bluetooth a standard for short range wireless networking Proceedings. 15th Annual IEEE International ASIC SOC Conference, Rochester, NY, USA, 25 28 Sept. 2002 , pp. 474 475. 2002. http ieeexplore.ieee.org xpls abs all.jsp?arnumber 1158106 ref , Cypress WirelessUSB , Nordic Semiconductor ref Nordic Semiconductor. http www.nordicsemi.com files Product data sheet Preliminary Product Specification nRF24LU1P v1 2.pdf nRF24LU1 Preliminary Product Specification v1.2 ref , Texas Instruments LPRF , z wave and Wavenis devices. For basic data rate Bluetooth the minimum deviation is 115 kHz. Generalization In a GFSK modulator, everything is the same as an Frequency shiftkeying FSK modulator except that before the baseband pulses 1, 1 go into the FSK modulator, it is passed through a gaussian filter to make the pulse smoother so to limit its spectral width. Gaussian filtering is one of the very standard ways for reducing the spectral width, it is called pulse shaping . If we use 1 for math f c f d math and 1 for math f c f d math , once when we jump from 1 to 1 or 1 to 1, the modulated waveform changes rapidly, which introduces large out of band spectrum. If we change the pulse going from 1 to 1 as 1, .98, .93 ..... .96, .99, 1, and we use this smoother pulse to modulate the carrier, the out of band spectrum will be reduced. ref http www.palowireless.com infotooth knowbase radio 109.asp www.palowireless.com GFSK Differences & Advantages over FSK Modulation ref References Reflist telecomm stub wireless stub Category Quantized radio modulation modes de Gaussian Frequency ShiftKeying es Modulaci n por desplazamiento de frecuencia gausiana ko pl GFSK ru GFSK ... more details
Modulation techniques Multiple frequency shiftkeying MFSK is a variation of frequency shiftkeying FSK that uses more than two frequencies. http sharon.esrac.ele.tue.nl mirrors zl1bpu MFSK is a form of M ary orthogonal modulation , where each symbol consists of one element from an alphabet of orthogonal waveforms. M, the size of the alphabet, is usually a power of two so that each symbol represents log sub 2 sub M bits. M is usually between 2 and 64 Error Correction is generally also used How it works Like other M ary orthogonal schemes, the required Eb N0 E sub b sub N sub 0 sub ratio for a given probability of error decreases as M increases without the need for multisymbol coherent detection. In fact, as M approaches infinity the required E sub b sub N sub 0 sub ratio decreases asymptotically to the Shannon limit of 1.6 decibel dB . However this decrease is slow with increasing M, and large values are impractical because of the exponential increase in required bandwidth. Typical values in practice range from 4 to 64, and MFSK is combined with another forward error correction scheme to provide additional systematic coding gain. Types Defined examples of a multiple frequency shiftkeying system include dual tone multi frequency DTMF , which is used in touch tone phones and the Multi frequency trunk signals used in Twentieth Century telephone exchanges. These signals are distinctive when received aurally. Their main feature is a rapid succession of tones with almost musical quality. ref cite web url http xoomer.alice.it ham radio manuals scanning Digitalsignalsfaq.html author Scalsky, S. and Chace, M. title Digital Signals Frequently Asked Questions Version 5 , Section 1 D ... web author Dehio, Leif title MFSK systems Multi Frequency ShiftKeying url http www.signals.taunus.de ... 2008 01 06 refend DEFAULTSORT Multiple Frequency ShiftKeying Category Quantized radio modulation modes Category Telephony signals it Multiple frequency shiftkeying pl MFSK ... more details
Minimal ShiftKeying VMSK , that were supposed to increase Internet downloading speeds and the speed ...class infobox style width 22em colspan 2 style font size larger Disputed Science br Very Minimum ShiftKeying modulation style vertical align top Disciplines Radio technology Radio modulation modes style vertical align top colspan 2 Core Tenets style vertical align top colspan 2 VMSK claims to achieve high speed data transfer while maintaining a very narrow bandwidth. Some experts see this as a direct violation of the mathematical principles of communications developed by Claude Shannon, a theoretical boundary that limits the maximum achievable channel capacity for a given bandwidth and signal to noise ratio. style vertical align top Year proposed 1995 style vertical align top Proponents Harold Hal R. Walker VMSK , for very minimum shiftkeying modulation, is one of several ultra narrow band modulation UNBM methods claimed to send high speed digital data through very low Bandwidth signal processing bandwidth or narrowband channels. VMSK is a variant of phase shiftkeying , ref name strassberg cite web title VMSK 2 high bps, low BW, allegedly no snake oil url http www.edn.com article CA47127.html work EDN Magazine author Dan Strassberg date 2000 08 17 ref not related to minimum shiftkeying . Claims versus analysis Walker claims that with VMSK, Efficiencies up to 15 Spectral efficiency bits sec Hz are now being achieved in usable hardware with Carrier to noise ratio C N ratios better than that obtainable using FM broadcasting FM , BPSK or QPSK . ref cite journal author Walker, H.R. title VPSK and VMSK modulation transmit digital audio and video at 15 bits sec Hz journal IEEE Transactions on Broadcasting volume 43 issue 1 date March 1997 url ref Analysis by third parties have concluded that no ultra narrow band modulation UNBM method, which includes very minimum shiftkeying VMSK and VPSK, can have substantially greater efficiency than conventional methods. ref cite journal ... more details
Mergeto Phase shiftkeying OQPSK date March 2009 Orphan date February 2009 In telecommunication , filtered symmetric differential phase shiftkeying FSDPSK is a method of encoding information for digital transmission telecommunications transmission in which A 0 bit is encoded as a 90 change in the carrier wave carrier phase waves phase , and a 1 bit is encoded as a 90 change in the carrier phase Abrupt phase transitions are smoothed by filtering or other functionally equivalent pulse shaping techniques. See also Phase shiftkeying References FS1037C Category Communication circuits telecomm stub ... more details
wiktionary keyingKeying may refer to Keying, the installation of cryptography cryptographic key material into a device Keying graphics , a technique for compositing two full frame images together Keying ship Keying ship , a Chinese junk which sailed to the U.S. and Britain in 1847 1848 Keying telecommunications , a form of modulation where the modulating signal takes one of two or more values at all times Keying vandalism , vandalism by scratching paint with a key See also Key disambiguation disambiguation ... more details
dablink For quantum mechanical amplitude, see probability amplitude . For the video game of the same name, see Amplitude video game . Peak to Peak redirects here. For the school of that name, see Peak to Peak Charter School Refimprove date October 2007 Amplitude is the magnitude mathematics magnitude ... axis, the amplitude is visually represented by the vertical distance between the extrema ... called the amplitude. ref Cite book author1 Knopp, Konrad author2 Bagemihl, Frederick authorlink1 ... 0 486 69219 1 page 3 ref Concepts Peak to peak amplitude Peak to peak amplitude is the change between peak highest amplitude value and trough lowest amplitude value, which can be negative . With appropriate ... a common way of specifying amplitude, but sometimes other measures of amplitude are more appropriate. Peak amplitude In audio system measurements , telecommunications and other areas where the wikt ... sinusoidal , peak amplitude is often used. This is the maximum absolute value of the signal. Semi amplitude Semi amplitude means half the peak to peak amplitude. ref name Tatum Tatum, J. B. http orca.phys.uvic.ca ... 2008 08 22. ref It is the most widely used measure of orbital amplitude in astronomy and the measurement ... 22 ref For a sine wave, peak amplitude and semi amplitude are the same. Some scientists ref Regents ... of Light What is the Amplitude of a Wave? 1996. Retrieved 2008 08 22 ref use amplitude or peak amplitude to mean semi amplitude, that is, half the peak to peak amplitude. ref name Tatum Root mean square amplitude Root mean square RMS amplitude is used especially in electrical engineering the RMS is defined ... www.comdis.wisc.edu vcd202 rms.html RMS Amplitude . Retrieved 2008 08 22 ref For complex waveforms, especially non repeating signals like noise, the RMS amplitude is usually used because it is both ... amplitude and not, in general, to the square of the peak amplitude . ref Ward, Electrical ... curve br 1 Peak amplitude math scriptstyle hat U math , br 2 Peak to peak amplitude Peak to peak ... more details
Keying is a family of modulation forms where the modulating signal takes one of two or more values at all times. The goal of keying is to transmit a digital signal over an analogue channel. The name derives from the Morse code key used for Telegraphy telegraph signaling. Modulation is the general technique of shaping a signal to convey information. When a digital message has to be represented as an analogue waveform, the technique and term keying or digital modulation is used. Keying is characterized by the fact that the modulating signal will have a limited number of states or values at all times, to represent the corresponding digital states commonly zero and one, although this might depend on the number of symbol data symbols used . This is in contrast to analogue modulation , where an analogue signal is transmitted over an analogue channel, and where the modulated analogue signal will have an infinite number of meaningful states. Furthermore, note that keying or digital modulation applies to transmitting a digital signal over an analogue passband channel . When a digital signal is to be transmitted over an analogue baseband channel , the modulation technique is termed line coding . Several keying techniques exist, including phase shiftkeying , frequency shiftkeying and amplitudeshiftkeying . Bluetooth , for example, uses phase shiftkeying to exchange information between devices. An overview of keying techniques is given on the modulation page. Category Telecommunications terms telecomm term stub ... more details
Modulation techniques Unreferenced date August 2011 On off keying OOK the simplest form of amplitudeshiftkeying ASK modulation that represents digital data as the presence or absence of a carrier wave . In its simplest form, the presence of a carrier for a specific duration represents a Binary numeral system binary one, while its absence for the same duration represents a binary zero. Some more sophisticated schemes vary these durations to convey additional information. It is analogous to unipolar encoding line code . On off keying is most commonly used to transmit Morse code over Radio frequency radio frequencies referred to as CW continuous wave operation , although in principle any digital encoding scheme may be used. OOK has been used in the ISM band s to transfer data between computer s, for example. OOK is more Spectral efficiency spectrally efficient than FSK, but more sensitive to noise. In addition to RF carrier waves, OOK is also used in optical communication systems e.g. IrDA . In aviation, some possibly unmanned airports have equipment that let pilots key their VHF radio a number of times in order to request an Automatic Terminal Information Service broadcast, or Pilot Controlled Lighting turn on runway lights . See also Unipolar encoding External links http www.maxim ic.com appnotes.cfm an pk 4439 CMP ELK12 Application Note I m OOK. You re OOK? Morse code state uncollapsed Bit encoding state uncollapsed Category Quantized radio modulation modes Category Fiber optic communications Category Amateur radio ar bn ko it On off keying ja ... more details
Junk Keying Infobox ship career Hide header Ship country Ship flag Ship name Keying Ship ordered ... Keying zh c p q y ng , named after the Manchu official Qiying the English name is based ... Kingdom Britain between 1846 and 1848. Keying had been purchased in August 1846 in secrecy by British ... . She was commanded by Captain Charles Alfred Kellett , also British. Keying left Hong Kong in December ... Waugh 1814 1885 , depicting the Junk Keying moored in New York harbour in 1847 watercolor on canvas, c. 1853 1855, Museum of the City of New York . The Keying was the first ship from China to visit ... 1847, and was received with great fanfare. The Chinese crew of Keying were understandably angry ... . Twenty six of them left Keying and returned to Canton on board the Candace , which sailed 6 October 1847. Keying stayed several months in New York. 4,000 visitors a day paid 25 cents to board the ship and observe its design and crew. P. T. Barnum had a copy of Keying built in Hoboken Barnum claimed he had it towed from China , and exhibited it with a crew which may have included some of the Keying ... negroes or mulattoes , so probably no real Keying crew were present. Keying also moored in Boston on November ... visit Image KeyingMedal.jpg thumb 300px The medal made for the arrival of the Junk Keying in Britain. Keying next sailed to Britain. A storm on 28 February wrecked her two boats, ripped the foresail ... s. During the repair of the rudder the second mate drowned. Keying was fast, as was noted by the press The Keying next visited Boston, whence she sailed direct for London on the 17th of February ... London News , 1848 Keying reached Britain in March 1848, and a medal was made in honor of her ... 150px Illustrated London News, 1848, full article. Keying was praised by the British as excellent ... family. The Illustrated London News of 29 July 1848 described the visits to the Keying as follows The ROYAL CHINESE JUNK KEYING manned by a Chinese Crew. Visitors received by a Mandarin of rank ... more details
Orphan date December 2009 In wireless technology, handover keying Hokey refers to maintaining a secure connection seamlessly while migrating from one wireless network to another. External links IETF http www.ietf.org html.charters hokey charter.html Working Group http www.networkworld.com news 2007 073007 ietf qa.html Interview with Russ Housley , chair of the Internet Engineering Task Force Category Wireless networking Wireless stub ... more details
wiktionarypar shiftShift generally means to change position . For other meanings, see wiktionary. Shift may refer to Things also known as only Shift Gear shift , to change gears in a car Shift work , an employment practice Shift string technique Shift music , a change of level in music Shift magazine Shift magazine , a former Canadian technology and culture magazine Shift weapon , an improvised knife used as a weapon Shift clothing , a simple kind of undergarment Shift the Ape , a character in The Chronicles of Narnia novel series Need for Speed Shift , a 2009 racing video game Shift 2 Unleashed , the 2011 sequel to the aforementioned video game Shift game Shift , an online video game series developed and presented by Armor Games . In mathematics and computing Shift key , a key on a computer keyboard Bit shift , a bitwise operator in computing Barrel shifter , a digital circuit that can shift a data word by a specified number of bits Arithmetic shift in telecommunication Logical shift Circular shift or bit rotation, often used in cryptography Shift operator , a linear operator in mathematics See also Compound words containing shift lookfrom Shift Red shift disambiguation Vowel shift , a change in the pronunciation of vowel sounds Paradigm shift , a change in basic assumptions within the ruling theory of science Tax shift , a fiscal policy Baseball positioning , where shift is a strategic alteration in defenders normal fielding locations Shapeshifting disambig de Shift ko nl Shift ja ru simple Shift ... more details
applications. A simple form of AM, often used for digital communications, is on off keying a type of amplitudeshiftkeying in which Binary numeral system binary data is represented by the presence ...Modulation techniques Amplitude modulation AM is a technique used in electronic communication, most commonly ... modulation , in which the Phase waves phase is varied. In the mid 1870s, a form of amplitude ... sine waves Forms of amplitude modulation In radio communication, a continuous wave radio frequency signal a sinusoid al carrier wave has its amplitude modulated by an audio waveform before transmission. In the frequency domain , amplitude modulation produces a signal with power concentrated at the carrier ... bandwidth to that of the modulating signal, and is a mirror image of the other. Amplitude modulation resulting in two sidebands and a carrier is called double sideband amplitude modulation DSB AM . Amplitude ... the types of amplitude modulation class wikitable Designation Description A3E double sideband double sideband a full carrier the basic Amplitude modulation scheme R3E Single sideband modulation ... and math phi c , math represent the carrier amplitude and initial phase, and are introduced for generality ... and that math min m t M. , math Amplitude modulation is formed by the product math y t , math ... represents the carrier amplitude, which is a constant that demonstrates the modulation index. The values ... index The AM modulation index is the measure of the amplitude variation surrounding an unmodulated ... in carrier amplitude and is defined as math h frac mathrm peak value of m t A frac M A , math where math M , math and math A , math were introduced above. So if math h 0.5 math , carrier amplitude ... signal with percentages of modulation are shown below. In each image, the maximum amplitude is higher ... of other modulation techniques Amplitude modulation signalling system AMSS , a digital system ... of radio emissions , for the emission types designated by the ITU Airband Quadrature amplitude ... more details
Orphan date February 2009 An amplitude gate also, slicer or slice amplifier is a electronic circuit circuit whose output is only the part of the input signal that lies between two amplitude boundary level values. ref http www.answers.com topic amplitude gate amplitude gate Definition and Much More from Answers.com Bot generated title ref References references Refimprove date June 2007 DEFAULTSORT Amplitude Gate Category Electronic circuits Electronics stub ... more details
Orphan date February 2009 Image Amplitude gb.png 300px thumb The amplitude of the supply current rises with increasing power consumption of the load. The Amplitude adjusting also referred to as Amplitude control enables the power control of electric loads, which are operated with AC voltage. A representative application is the heating control of industrial high temperature furnaces. Functionality Image Sinuslevel gb.gif 300px thumb The sinus oscillation does not change. Contrary to the conventional phase angle or full wave control , during amplitude control only the Amplitude of the sinusoidal supply current is changed. The level of the amplitude only depends on the consumed power. The sinus oscillation does not change. Because current and voltage are in phase, only real power is taken from the mains for amplitude control. So the current consumption from the mains is considerably lower than the current consumption in case of phase angle operation. Advantages The continuous current flow causes a mild operation of the used heater elements and consequently significant longer lifetimes are realized. Depending on the ambient conditions the lifetime can be twice as long. Especially the surface damage of the heater elements at thresholds can be reduced. The amplitude control eliminates the flicker effect s and harmonics, as usual for Thyristor units, so that the standard specifications according to European Standard EN 61000 3 2 and EN 61000 3 3 are observed. Reactive power compensation is not required, reducing equipment costs. Applications Sinus units or IGBT power converters for power control of Resistance heatings Silicon carbide SC heater elements Molybdenum disilicide MoSi2 heater elements Infralight radiators Literature Manfred Schleicher, Winfried Schneider Electronic power units . BR ISBN 3 935742 05 3, ISBN 978 3 935742 05 4 http www.literaturfas620en.jumo.info ... with amplitude control.html JUMO IGBT Power converter with amplitude control Category Electric ... more details
A sinusoidal waveform is said to have a unity amplitude when the amplitude of the wave is equal to 1. math x t Asin wt math where A 1. This terminology is most commonly used in Digital Signal Processing and is usually associated with the Fourier series and Fourier Transform sinusoids that involve a duty cycle , , and a defined fundamental period , T sub o sub . Category Digital signal processing signal processing stub ... more details
Amplitude distortion is distortion occurring in a system , subsystem, or device when the output amplitude is not a linear function of the input amplitude under specified conditions. Generally, output is a linear function of input only for a fixed portion of the transfer characteristics. In this region, I sub c sub I sub b sub where Ic is collector current and Ib is base current, following linear relation y mx. When output is not in this portion, two forms of amplitude distortion might arise harmonic distortion intermodulation distortion Harmonic distortion The creation of harmonics of the fundamental frequency of a sine wave input to a system. Intermodulation distortion This form of distortion occurs when two sine waves of frequencies X and Y are present at the input, resulting in the creation of several other frequency components, whose frequencies include X Y , X Y , 2X Y , 2Y X , and generally mX nY for integer m and n. Generally the size of the unwanted output falls rapidly as m and n increase. Due to the additional outputs, this form of distortion is definitely unwanted in audio, radio and telecommunication amplifiers, and it occurs for more than two waves as well. In a narrowband system such as a radio communication system, unwanted outputs such as X Y and 2X Y will be remote from the wanted band and so be ignored by the system. In contrast, 2X Y and 2Y X will be close to the wanted signals. These so called third order distortion products third order as m n 3 tend to dominante the non linear distortion of narrowband systems. Amplitude distortion is measured with the system operating under steady state conditions with a sinusoidal input signal information theory signal . When other frequencies are present, the term amplitude refers to that of the fundamental only. External links http tenwatts.blogspot.com 2007 12 audio lesson.html Arcane Radio Trivia amplitude distortion article w examples http mwrf.com Articles Index.cfm?Ad 1&ArticleID 16649 RF article with trigonometry ... more details
Refimprove date June 2007 In quantum physics, the scattering amplitude is the amplitude of the outgoing spherical wave relative to the incoming plane wave in the stationary state scattering process. ref http eu.wiley.com WileyCDA WileyTitle productCd 0470026790.html Quantum Mechanics Concepts and Applications By Nouredine Zettili, 2nd editon, page 623. ISBN 978 0 470 02679 3 Paperback 688 pages January 2009, 2008 ref The latter is described by the wavefunction math psi mathbf r e ikz f theta frac e ikr r , math where math mathbf r equiv x,y,z math is the coordinate vector math r equiv mathbf r math math e ikz math is the incoming plane wave with the wave vector math k math along the math z math axis math e ikr r math is the outgoing spherical wave math theta math is the scattering angle and math f theta math is the scattering amplitude. The dimension of the scattering amplitude is length . The differential Cross section physics cross section is given as math frac d sigma d Omega f theta 2 . math In the low energy regime the scattering amplitude is determined by the scattering length . Partial wave expansion In the partial wave expansion the scattering amplitude is represented as a sum over the partial waves, ref http galileo.phys.virginia.edu classes 752.mf1i.spring03 Scattering II.htm Michael Fowler 1 17 08 Plane Waves and Partial Waves ref math f theta sum l 0 infty 2l 1 f l k P l cos theta , math where math f l k math is the partial amplitude and math P l cos theta math is the Legendre polynomial . The partial amplitude can be expressed via the S matrix element math S l e 2i delta l math and the scattering phase math delta l math as math f l frac S l 1 2ik frac e 2i delta l 1 2ik frac e i delta l sin delta l k frac 1 k cot delta l ik . math X rays The scattering length for X rays is the Thompson scattering length or classical electron radius , math r 0 math . Neutrons The nuclear neutron scattering process involves the coherent neutron scattering length, often described ... more details
In theoretical physics , the Veneziano amplitude refers to the discovery made in 1968 by Italy Italian theoretical physicist Gabriele Veneziano that the Euler beta function , when interpreted as a scattering amplitude , has many of the features needed to explain the physical properties of Strong interaction strongly interacting meson s, such as symmetry and duality. ref cite journal last Veneziano first G. authorlink Gabriele Veneziano year 1968 title Construction of a crossing symmetric, Regge behaved amplitude for linearly rising trajectories journal Nuovo Cimento A volume 57 pages 190 7 ref This discovery can be considered the birth of String Theory . ref cite book last Di Vecchia first P. chapter The Birth of String Theory pages 59 118 url http www.springerlink.com content w212062126125881 fulltext.pdf editor1 last Gasperini editor1 first Maurizio editor2 last Maharana editor2 first Jnan title String Theory and Fundamental Interactions Gabriele Veneziano and Theoretical Physics Historical and Contemporary Perspectives publisher Springer publisher Springer series Lecture Notes in Physics year 2008 volume 737 isbn 978 3 540 74232 6 ref See also Dual resonance model References references string theory stub Category Theoretical physics it Ampiezza di Veneziano ... more details
orphan date March 2011 Amplitude Panning is a technic in sound engineering where the same sound signal is applied to a number of loudspeaker s in different directions equidistant from the listener. Then, a virtual source appears to a direction that is dependent on amplitude s of the loudspeakers. The direction may not coincide with any physical sound source. Most typically amplitude panning has been used with stereophonic loudspeaker setup. However, it is increasingly used to position virtual sources to arbitrary loudspeaker setups. History First invented by Blumlein in early 1930s, original stereophony was a system that converts the phase difference of the signals recorded by a pair of microphone s to the amplitude difference of in phase input signals to two loudspeakers ref name blumlein A. D. Blumlein Improvements in and relating to sound transmission, sound recording and sound reproducing systems. British Patent No. 34657, 1933. ref . Operation Assuming free field sound propagation , it has been shown that the sound field presented by these two transducer s can deliver an appropriate phase difference between the positions of listener s ears at low frequencies, where the relation between the position of phantom image and the corresponding amplitude ratio may be summarized by the so called sine law ref H. Clark, G. Dutton, P. Vanderlyn The stereophonic recording and reproducing system. IRE. Trans. Audio 5 1957 96 111. ref similarly, thetangent law ref V. Pulkki, M. Karjalainen Localization of amplitude panned virtual sources I Stereophonic panning. Journal of the Audio Engineering Society 49 2001 739 752. ref . The system was designed to work approximately below 1 kHz, above which the given phase difference becomes ambiguous, and so does the position of the sound ... configurations, and the results showed that the amplitude panning method is not as efficient in presenting ... . References reflist DEFAULTSORT Amplitude Panning Category Stereophonic sound Category Audio engineering ... more details
Amplitude of accommodation AA is a measurement of the human eye eye s ability to focus clearly on objects at near distances i.e. accommodation eye accommodation . This eye focusing range for a child is usually about 5&ndash 7.5 cm 2&ndash 3 inches . For a young adult, it is 10&ndash 15 cm 4&ndash 6 inches . The focus range for a 45 year old adult is about 50 cm 20 inches . For an 80 year old adult, it is 1.5 m 60 inches . ref http www.vision therapy.com Glossary of Terms.htm www.vision therapy.com ref The average amplitude of accommodation, in diopters , for a patient of a given age may be estimated by Hofstetter s formula 18.5 minus one third of the patient s age in years. ref Scheiman, Mitchell and Wick, Bruce. Clinical Management of Binocular Vision. Lippincott, New York. 1994. ref See also Convergence insufficiency Eye examination Negative relative accommodation Positive relative accommodation Presbyopia References reflist External links http www.ijo.in article.asp?issn 0301 4738 year 2005 volume 53 issue 2 spage 105 epage 108 aulast Abraham Category Ophthalmology ... more details
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