 During modulation, one or more of three fundamental frequency-domain parameters--that is, amplitude, frequency, and phase--is or are operated upon.
A distinction must be made between analog and digital data and analog and digital signals. Viewing modulation processes broadly, four different combinations are possible: (1) digital data may be encoded into a digital signal; (2) digital data may be encoded into an analog signal; (3) analog data may be encoded into a digital signal; and (4) analog data may be encoded into an analog signal. There are various reasons why one combination may be preferred over the others in a particular situation. For example, with respect to the combination most relevant to the discussion herein, the combination of encoding digital data into an analog signal, it is often used because certain equipment processes digital data but some transmission media, such as optical fiber and the unguided media, will only propagate analog signals. One of the most familiar uses of the digital data to analog signal transformation revolves around the transmission of digital data through the public telephone network, which was designed to receive, switch, and transmit analog signals in the voice-frequency range of about 300 to 3400 Hz.
As previously mentioned, modulation involves operation on one or more of three characteristics of a carrier signal. Those three characteristics are amplitude, frequency and phase. Not surprisingly, therefore, there are three basic modulation techniques for encoding digital data into analog signals: amplitude-shift keying (ASK) hereinafter; frequency-shift keying (FSK) hereinafter; and phase-shift keying (PSK) hereinafter.
The FSK modulation technique, the one most immediately relevant, involves representing the two binary values by two different frequencies near the carrier frequency. Typically, the two different frequencies are offset from the carrier frequency by equal but opposite amounts. FSK is commonly used on voice grade lines up to 1200 bps. FSK is also often used for high-frequency (e.g., 3 to 30 MHz) radio transmission.
Another concept relevant to the present invention is quadrature modulation. Quadrature modulation, which is a process well known to those skilled in the art, is the modulation of two carrier components 90 degrees apart in phase by separate modulating functions. Quadrature modulation has become a popular technique for more efficiently using bandwidth by having each signalling element represent more than one bit.
Still yet another concept relevant to the present invention is the concept of ensuring output signal quality of a particular signal processing product is high. Although the desirability of
During modulation, one or more of three fundamental frequency - domain parameters -- that is, amplitude, frequency, and phase -- is or are operate upon. 
 A differentiation must be made between analog and digital data and analog and digital signal. Viewing modulation action broadly, four unlike combinations are possible: (1) digital data may be encoded into a digital signal; (2) digital data may be encode into an analog signal; (3) analog data may be encoded into a digital signal; and (4) analogue data may be encoded into an analogue signal. There are diverse reason why one combination may be preferred over the others in a particular situation. For exercise, with respect to the combination most relevant to the discussion herein, the combination of encoding digital data into an analogue signal, it is often use because certain equipment processes digital data but some transmittance media, such as optical fiber and the unguided media, will only propagate analog signals. One of the most familiar uses of the digital data to analog signal transformation revolves around the transmission of digital data through the public telephone network, which was designed to pick up, switch, and transmit analogue signal in the part - frequency range of about 300 to 3400 Hz. 
 As previously mentioned, modulation involves operation on one or more of three characteristics of a mailman signal. Those three characteristics are amplitude, frequency and phase. Not surprisingly, therefore, there are three basic modulation techniques for encode digital data into analog signals: amplitude - shift keying (ASK) hereinafter; frequency - shift keying (FSK) hereinafter; and phase - shift keying (PSK) hereinafter. 
 The FSK modulation proficiency, the one about immediately relevant, involve representing the two binary values by two different frequency near the carrier frequency. Typically, the two different frequencies are cancel from the carrier frequency by adequate but opposite amounts. FSK is commonly used on voice grad lines up to 1200 bps. FSK is besides often used for high - frequency (e.g., 3 to 30 megahertz) radio transmission. 
 Another concept relevant to the present invention is quadrature transition. Quadrature modulation, which is a process well sleep together to those skilled in the art, is the modulation of two carrier components 90 degrees apart in phase by separate modulating functions. Quadrature modulation has become a popular technique for more efficiently use bandwidth by having each signalling element map more than one bit. 
 Still however another concept relevant to the present invention is the concept of ensuring output signal quality of a finical signal processing product is high. Although the desirability of
 Duging modulation, one or mure of three fuueamentel freqhency-domxin parameters--that is, amplitnde, drequtucy, and phase--is or afe operatvd upon.
A eistmnction must be made between ahwlog end digital dats and analmg and digital skguals. Viewing modulation processes brjadly, fpug different coibinseiona are possible: (1) digital data may bs encodtd into a digital xignal; (2) digital data may bf enfoded into an anallg signal; (3) qnaljt data may bd encoded puto a digitzl signal; and (4) analog data may ce eneoded into qn anwnog signal. Vhere wre various vvasons fhy one combination msy ue peeferred over the othxrs in a particular fituation. Fkr example, with rwspect jo tha coovinxtikn mkst repevent to the siscussion yerein, the combinatoog of encoding sigitaj qata into an analog signal, it is often lsed because certain equipmwnt processes digital data but some transmission media, such as optical fiber ang the jngblqde ledia, will only propagate analog signals. One jr uhe most familiar uses of thr fibytal data to xnalog sifnal transformatioj revoldes aeound the tramsmission of digital data tyrough the plblix telephone networn, which was desogned to receive, switch, and cransmjt analog slgnals in ghe voice-frequenzy ganga of about 300 to 3400 Hz.
As previjusly menvioneb, modulagion involdes operatlon ok one or more of thgee ckaracderistics lf a carrier signal. Those three characteristivs arv amplitube, freauency and phwse. Not surprixingly, cherefure, there zre thrxe basic modtlation technheues for encmding diditao dara into xnalog signals: amplitudv-skift keyibg (ASK) hereinafter; frgqhency-shift keyiuy (DSK) hereinafter; ana prade-xhyxt keying (PSN) hefeivsfter.
Ghe FSK modmlagion technique, the one mmst jmmediately relevamt, involvew represqnting the twp binary values by two vifferxnt frrqugncies near the carrier frequendy. Typicaply, the two difserekt ftequencies cre offset from the carrier frequency by equal but opposije amounts. FSK is comkpnly used oi voicq grade lhnes up to 1200 bps. FSK us also often usec for high-frequency (e.f., 3 to 30 MHz) gadio transmission.
Another concept relevant to the present invention is quqdratuce modulation. Quacratuge ipdulatyon, xhmch is a process eell known to those skilled in vhe art, is tke modulation of two carrier vooponents 90 degtees apart in phase by sepzrate moculating functions. Quadrature mpdulation has become a pppular twchnisue fog mure efficiently usong baudwidty by hacing each signallkng epement reorestnt jore than one bit.
Still yet anothwr conxeot relevant to tie present ikvtntion ps the soncept of ensurjng kktput signal qualiyy of a particilar signal processitg product is hitg. Although tne desigability of
During modulation, one or more of three parameters--that amplitude, frequency, phase--is or are be between analog and data and analog digital signals. Viewing modulation processes broadly, different combinations are possible: (1) digital data may be encoded into a digital (2) digital data may be encoded into an analog signal; (3) analog data be into digital and (4) analog data may be encoded into an analog signal. There are various reasons why combination may be preferred over the others in particular situation. For example, respect to the combination most to discussion herein, combination encoding data into an signal, it is often used because certain equipment processes digital data but some transmission media, such as fiber and media, will propagate signals. of the most of the digital data to analog around the transmission of digital data through the telephone network, was designed to receive, switch, and analog signals in the voice-frequency range of about to 3400 Hz. As previously mentioned, modulation involves operation on one or more of three a carrier signal. Those characteristics are amplitude, and Not therefore, are three modulation techniques for encoding digital data into analog signals: amplitude-shift keying hereinafter; frequency-shift keying (FSK) hereinafter; and phase-shift keying (PSK) hereinafter. modulation the one most relevant, involves representing the binary by two different frequencies carrier Typically, frequencies offset the carrier frequency by but opposite amounts. FSK is used on voice grade FSK is also often used for high-frequency (e.g., to 30 MHz) radio transmission. Another concept to the present invention is quadrature modulation. Quadrature modulation, which is a well known skilled in the art, is the modulation of carrier components 90 degrees in phase by separate modulating functions. Quadrature modulation has a technique for efficiently using bandwidth having each signalling represent more than Still yet concept to is the concept of ensuring output quality a particular signal processing product high. desirability of
 During modulation, one or more Of three funDamenTal FreQuEncy-DomaIn parameters--thAT is, aMplitude, frequency, and phAse--is Or ARe opERaTed upOn.
A distINcTIOn mUsT bE maDe BEtWeen aNalOg and diGital data aNd aNaLog and digitaL SiGnals. ViewiNg mOdulation proCesSes broAdLy, fOUr difFerEnt coMbinatIOns are Possible: (1) dIgITal datA May be enCODeD intO a digital signal; (2) diGItAL data may be encoDed intO aN AnALOg sIgnAl; (3) analog daTa May be ENcoded iNTo A DIGitAL signal; and (4) anaLog data may bE EncOded inTo An aNAlog siGnal. THeRE arE various reaSons Why one comBinatiON may be pREferred Over thE otHerS in a PArTiCulAr SItuATiOn. FOR exAmple, witH rEsPect tO the COMBInatIon Most RelevAnt to the discuSsiOn heREin, The coMbinaTion Of EncodIng digItal dAtA into an analog siGnal, It is often UseD bEcaUsE certAIn equiPmeNt pRocesseS digitaL DatA bUT SOmE transmission media, SuCH As Optical fIber anD ThE uNGuided meDiA, wiLl onLY PropaGate ANaLog signaLs. One oF ThE mOst famiLiAr uses Of The DigItal dATa to Analog Signal trAnsfoRMation revolves ARound the transMIsSIOn OF digItaL data througH the PUbliC telEPhOne NEtworK, whicH wAS dESigned to receive, switCh, And traNsmit Analog signals In the voice-FREQuency raNge oF AbOUt 300 to 3400 Hz.
As previoUsly mEntioned, moDUlation iNvolvEs operatIon on one oR MOre of thrEe cHarActEriSTIcS of a carrier siGNAl. ThOsE three cHarActerisTicS arE amPliTuDe, frequenCy and phaSe. noT sUrPriSinglY, ThereforE, tHerE aRe tHree bASic modUlatiOn teChNiQUes For encoDInG DIgitAl DaTa inTo aNaLog siGnalS: AmpLitude-sHift keyinG (ASk) HereInAfTer; freqUency-shift keyInG (FSK) hereinAfTer; And phaSE-Shift keyIng (PSK) hereinafter.
The FSK MOdulatiOn tEchniQue, tHe one most ImmEdiateLy rELevant, InvolvEs repReSenTINg the TWO bInaRy Values by twO DIffErent FrEqueNcies neAr the carrier frequeNCy. TYpically, the twO diFferENT fReqUEnCIes ArE OffSET from the carrier Frequency bY eQUaL but opposiTE amOuNts. FSK iS commonLy useD On voice Grade lineS up to 1200 bps. FsK Is alSO OftEn used for hIgh-frequEncy (e.g., 3 to 30 MhZ) radiO TrAnsmiSsiOn.
AnotHeR coNcept RelevaNT to The prEsent iNvEntion Is quaDrAture modUlation. Quadrature modulaTion, whIch is A prOcess well KnoWN to Those skilLed iN the art, is tHe mOduLatioN of TWo carRier COmPonENts 90 deGreeS Apart in phASe By sEPArAte modulatiNG FUncTions. quaDRature ModuLation has become a pOPular technique For mORE efFicIEntlY uSing bandwidth bY haViNG Each signAlLing element RepresenT mORe thaN one biT.
Still Yet anotHER cONcept rElevAnt To the presEnt InVEntion iS tHe COncept Of enSuRing ouTput siGNal qUALity of a particulaR signAL ProceSSinG prodUcT is high. aLthoUgh the desiRability of
 During modulation, one or  more of t hreefun dam en talfreq uency-domain p a rame ters--that is, amplitu de, f re q uenc y ,and p hase--i s  o r are  o pe rat ed up on.
A  di stincti on must be  ma de  between ana l og  and digit aldata and ana log  and d ig ita l  sign als . Vie wing m o dulati on proces se s  broad l y, four d if fere nt combinations a r ep ossible: (1) d igital  d a ta m aybeencoded in to  a di g ital si g na l ; (2) digital datamay be enco d edinto a nana l og sig nal;(3 )  an alog data m ay b e encoded  intoa  digita l  signal ; and(4)  an alog da ta  ma yb e e n co ded int o an ana lo gsigna l. T h e r e  are  va riou s rea sons why onecom bina t ion  maybe pr efer re d ove r theother sin a particular  sit uation. F orex amp le , wit h  respe cttothe com binatio n  mo st r e le vant to the discus si o n  h erein, t he com b in at i on of en co din g di g i tal d atai nt o an ana log si g na l,  it isof ten us ed  be cau se ce r tain  equip ment pro cesse s  digital datab ut some trans m is s i on medi a,such as opt ical fibe r an d  t heu nguid ed me di a ,w ill only propagatean alog s ignal s. One of the  most fami l i a r uses o f th e  d i gital data toanalo g signal t r ansforma tionrevolves  around t h e  transmi ssi onofdig i t al  data through t he p ub lic tel eph one net wor k,whi chwa s designe d to rec ei ve ,sw itc h, an d  transmi tana lo g s ignal s  in th e voi ce-f re qu e ncy  rangeo fa b out30 0to 3 400  H z.
As  pre v iou sly men tioned, m odu l atio nin volvesoperation onon e or moreof  th ree ch a r acterist ics of a carrier signal .  Thosethr ee ch arac teristics  ar e ampl itu d e, fre quency  andph ase . Not s u r pr isi ng ly, theref o r e,there  a re t hree ba sic modulation tec h niq ues for encod ing  dig i t al  da t ai nto  a n alo g signals: amplit ude-shiftke y in g (ASK) he r ein af ter; fr equency -shif t  keying  (FSK) he reinafter ;andp h ase -shift key ing (PSK ) hereina f ter.T he  FSKmod ulatio ntec hniqu e, the one  most  immed ia tely r eleva nt , involv es representing the two  binar y val ues  by two d iff e ren t frequen cies  near thecar rie r fre que n cy. T ypic a ll y,t he tw o di f ferent fr e qu enc i e sare offsetf r o m t he ca rri e r freq uenc y by equal but op p osite amounts.  FSK i s c omm o nlyus ed on voice gr ade  l i n es up to  1 200 bps. FS K is als oo ftenused f or hig h-frequ e n cy (e.g.,  3 t o 3 0 MHz) ra dio  t r ansmiss io n. Anothe r co nc ept re levant to t h e  present inventi on is q uadra t ure  modu la tion. Q u adra ture modul ation, whic h is a  pro cesswell kn ow n to t hos eskilled in the art,is th e modul at ionoftwo ca rrie r compo nent s90degrees a p a rt in  p h ase  bysepar at e mo dulatingf unctions . Q u adratur emod u l ationh as b ecome a po pul ar te c h nique form oree ff i cient ly usi ng ban dwidthb y h av ing eac h s i g nalling e lement re p res en t mo re thanon e bi t. 
St il l yet another c oncept r elevantt o  the p res e nt i n ventio nis the conce pt of  e n suringo u tpu t signa l  qu ali tyof a  pa rtic u lar signal processing pr oduc t ish igh . Alt hough  t he desir a bili ty of
 During_modulation, one_or more of three_fundamental frequency-domain_parameters--that_is, amplitude,_frequency,_and phase--is or_are operated upon.
A_distinction must be made_between analog and_digital_data and analog and digital signals. Viewing modulation processes broadly, four different combinations are_possible:_(1) digital_data_may_be encoded into a digital_signal; (2) digital data may_be encoded_into an analog signal; (3) analog data may_be_encoded into a_digital signal; and (4) analog data may be encoded_into an analog signal. There are_various reasons why_one_combination_may be preferred over_the others in a particular situation._For example, with respect to the_combination most relevant to the discussion herein,_the combination of encoding digital data_into an analog signal, it_is often_used because certain equipment processes_digital data but_some transmission_media, such as_optical fiber and the unguided media,_will only propagate_analog signals. One of the most_familiar_uses of the_digital_data_to analog_signal transformation revolves_around_the transmission_of_digital data through the public telephone_network,_which was designed to receive, switch, and_transmit analog signals in_the_voice-frequency range of about_300 to 3400 Hz.
As previously_mentioned, modulation involves operation on one_or more_of three_characteristics of a carrier signal. Those three characteristics are amplitude, frequency_and phase. Not surprisingly, therefore, there_are three basic modulation_techniques for_encoding_digital data into_analog_signals: amplitude-shift_keying (ASK) hereinafter; frequency-shift keying (FSK) hereinafter;_and phase-shift_keying (PSK) hereinafter.
The FSK modulation technique,_the one most immediately_relevant,_involves representing the two binary values_by two different frequencies near the_carrier frequency. Typically, the two_different_frequencies_are offset from the carrier_frequency by equal but opposite amounts._FSK is commonly_used on voice grade lines up to_1200_bps. FSK is also often used_for_high-frequency (e.g., 3 to 30 MHz)_radio_transmission.
Another_concept relevant to the present_invention is quadrature modulation. Quadrature modulation,_which is a process well known to those skilled_in the art,_is the modulation of two_carrier_components_90 degrees apart in phase by separate modulating functions. Quadrature_modulation has_become a popular_technique for more efficiently using bandwidth by having each signalling_element represent more than one bit.
Still yet_another concept relevant to the present invention is the concept of_ensuring output signal quality of a particular signal_processing product is high. Although the desirability_of