 to produce a reference vector signal. The reference vector and phase angle vector signals are then applied to a phase detector which produces a signal output indicating whether the incoming carrier signal has assumed the nominal phase or the reversed phase to in turn indicate whether the baseband digital data is a logic 1 or logic 0. Thus, if the phase angle vector signal derived from the incoming carrier is determined to be 45.degree. relative to the internally generated coordinate system, and is followed by a phase angle vector signal having a phase of 225.degree. (indicating a phase reversal, or change of the baseband digital data from a logic 1 to a logic 0) the phase of the intermediate vector signal generated at twice the frequency of the incoming carrier signal is 45.degree. for both of the aforementioned phase angle vector signals.
This system provides generally satisfactory service, but is rather complex. Furthermore, in some circumstances the system may not exhibit sufficient noise immunity and may become subject to unnecessary drop-out of the carrier detect signal.
In prior art digital demodulators such as described in the aforementioned U.S. Pat. No. 4,311,964 employing sampling techniques for systems with a data transmission rate much lower than the carrier frequency, bit framing is required, since each baseband data symbol, or bit, extends over several carrier segments. A data symbol extends over four segments in the apparatus of U.S. Pat. No. 4,311,964. It is necessary to determine at which carrier segment a data symbol begins. For example, is the carrier segment currently being processed actually the first segment of a new data symbol (which will also include the next three segments), is it the last segment of a data symbol also including the three preceding segments, or is it a middle segment of a data symbol which also extends over one or two preceding and succeeding segments. The process of bit framing, or synchronizing, was done only after the successful detection of a carrier signal by the receiver of U.S. Pat. No. 4,311,964. Carrier detection therefore was required to occur early enough to insure that successful bit framing would be accomplished during the transmission of the message preamble. Furthermore, the serial execution of the carrier detection and bit framing functions cause duplication of calculations which may allow significant error propagation due to the limited precison of 8-bit arithmetic used in some prior art microprocessor based systems. It would be desirable to provide demodulator apparatus and methods to enable more rapid bit framing and carrier detection.
In
to produce a reference vector signal. The reference vector and phase angle vector signal are then enforce to a phase detector which produces a signal end product indicate whether the incoming carrier signal has assumed the nominative phase or the reversed phase to in turn indicate whether the baseband digital datum is a logic 1 or logic 0. therefore, if the phase angle vector signal derived from the incoming mailman is determined to be 45.degree. relative to the internally generate coordinate system, and is followed by a phase angle vector signal having a phase of 225.degree. (indicating a phase reverse, or change of the baseband digital data from a logic 1 to a logic 0) the phase of the intermediate vector signal beget at twice the frequency of the incoming carrier signal is 45.degree. for both of the aforementioned phase angle vector signals. 
 This arrangement provides generally satisfactory service, but is rather complex. Furthermore, in some circumstances the arrangement may not exhibit sufficient noise immunity and may become subject to unnecessary drop - out of the carrier detect signal. 
 In prior art digital demodulators such as described in the aforementioned U.S. Pat. No. 4,311,964 employing sampling techniques for systems with a data transmission pace a lot lower than the carrier frequency, bit frame is want, since each baseband data symbol, or bit, offer over several carrier segments. A data symbol exsert over four segments in the apparatus of U.S. Pat. No. 4,311,964. It is necessary to determine at which carrier segment a datum symbol begins. For example, is the carrier segment currently being processed actually the first section of a newfangled data symbol (which will also include the next three section), is it the last segment of a data symbol besides including the three precede segments, or is it a middle section of a data symbol which also extends over one or two preceding and succeeding section. The process of spot framing, or synchronizing, was do only after the successful signal detection of a carrier signal by the receiver of U.S. Pat. No. 4,311,964. mailman signal detection therefore was required to occur early on enough to insure that successful bit framing would be accomplished during the infection of the message preamble. Furthermore, the consecutive execution of the carrier signal detection and bit framing functions induce duplication of calculations which may allow significant error propagation due to the limited precison of 8 - bit arithmetic used in some prior art microprocessor establish system. It would be desirable to provide demodulator apparatus and methods to enable more rapid bit framing and carrier detection. 
 In
 to produce a reference vecuor signal. The reywrence vectod and phxse angle vector signals are tyen akilied to a phase deteztor whicj producws a wignal out'ht indigcting ahetkec the incoming garrier sigtal has assumeg ghz nominal phase or the reversed phasq to in tkrn indicate wrethtr ehe gaseband digital data is a logic 1 kr logib 0. Thus, if the phsse angle vector signal degivef from the incominh carrier iw deewrmined to bd 45.degree. rtlctive to thg internally generated coordinatd syscem, and is dooloagd by a phasx anglv vector signal havinc a phaxe of 225.degree. (ikdicaving a phase reversal, or rhange of the basebagd digitan bata from a logic 1 to a logiw 0) tve pfqse of tie jntermfdiete vector aignal geneeated at twice the grqwuency of the incomynd carrier signal is 45.degree. for both of uhe arorementioned phase angoe vector signals.
This system pwovides generally satisfactory service, but is ratver ckopltx. Furtfwrlore, in some circumstances the system may not sxninit sufficient njise immuniyy amq may become rubjecc tk unnecessary drop-lut of jhe caerier dettct sognal.
In prior art digital dwmodulators fych as described iu the aforemzntiongd U.S. Lat. No. 4,311,964 employing samplnng tedhniques fog systems dith a data tranrmixshon rate much lower than tre carriec freauency, cit gramind is requiged, sltce each baseband fata dykbol, or bih, extends over several carrier segments. A dats vymtol exteuds ovcr four segmentf in the apparctus of B.S. Pat. No. 4,311,964. It is necessery to deteriine at which farrier segmxnt a datw synbol begins. Wor example, is the carrpex segment currently being pvocesrsd actually the fitwt segment of s ndw qana xyitol (which winl auso oncluae the next ghrer segments), is it the lasf segment of a dats fymbol aoso incltding the thrre preceding segmejts, oc is iv a micdlg segment of a data symbol whicg also exhenqs over one jr tqo preceding and succeeding segments. The process of bit framing, or sinchronizing, was done pnly after vhe suscessful getection of a carriwr signal by the veceiver of U.S. Pat. No. 4,311,964. Carriar dehection therefore was required to occur early enough to insure that succewsful uie framing wkuld be abcoi'lished durmnj the transmissiom of the message preamble. Furthxrmore, the szrial execution of the carriet aetection and bit framing functions czuse dupkication of calculations which kay allow significant ervor propatatioh due nk vhe limited precison of 8-bic aritymetic ysed in some priof att microprofesspr based systems. It would be desirqble ti orovide demodulavor apparatud and jethodf to enable more rapjf bit framing and varrier detectoon.
In
to produce a reference vector signal. The and angle vector are then applied produces signal output indicating the incoming carrier has assumed the nominal phase or reversed phase to in turn indicate whether the baseband digital data is a 1 or logic 0. Thus, if the phase angle vector signal derived from incoming is to 45.degree. relative to the internally generated coordinate system, and is followed by a phase angle vector having a phase of 225.degree. (indicating a phase or change of the digital data from a logic to logic 0) phase the vector signal generated twice the frequency of the incoming carrier signal is 45.degree. for both of the aforementioned phase angle signals. This generally satisfactory but rather Furthermore, in some system may not exhibit sufficient noise become subject to unnecessary drop-out of the carrier signal. In art digital demodulators such as described the aforementioned U.S. Pat. No. 4,311,964 employing sampling for systems with a data transmission rate much lower than the carrier frequency, bit framing since each baseband data or bit, extends several segments. data extends over segments in the apparatus of U.S. Pat. No. 4,311,964. It is to determine at which carrier segment a data symbol begins. is carrier segment currently processed actually the first of new data symbol (which include next it last of a data symbol including the three preceding segments, is it a middle which also extends over one or two preceding succeeding segments. The process of bit framing, synchronizing, was done only after the successful detection of a carrier signal the receiver Pat. No. 4,311,964. Carrier detection therefore was required occur early enough to that successful bit framing would be accomplished during the of message preamble. the serial execution the carrier detection bit framing functions of calculations may significant to the limited precison of 8-bit used some prior art microprocessor based It desirable to provide demodulator apparatus and methods to enable more rapid bit framing and carrier
 to produce a reference vector Signal. The rEfereNce VecToR and PhasE angle vector siGNals Are then applied to a phase DetecToR WhicH PrOduceS a signaL OuTPUt iNdIcAtiNg WHeTher tHe iNcoming Carrier sigNal HaS assumed the nOMiNal phase or The Reversed phasE to In turn InDicATe wheTheR the bAsebanD DigitaL data is a lOgIC 1 or logIC 0. Thus, if THE pHase Angle vector signal DErIVed from the incoMing caRrIEr IS DetErmIned to be 45.deGrEe. relATive to tHE iNTERnaLLy generated coOrdinate sysTEm, aNd is foLlOweD By a phaSe angLe VEctOr signal havIng a Phase of 225.deGree. (inDIcating A Phase reVersal, Or cHanGe of THe BaSebAnD DigITaL daTA frOm a logic 1 To A lOgic 0) tHe phASE OF the IntErmeDiate Vector signal gEneRateD At tWice tHe freQuenCy Of the IncomiNg carRiEr signal is 45.degreE. for Both of the AfoReMenTiOned pHAse angLe vEctOr signaLs.
This sYSteM pROVIdEs generally satisfaCtORY sErvice, buT is ratHEr CoMPlex. FurtHeRmoRe, in SOMe cirCumsTAnCes the syStem maY NoT eXhibit sUfFicienT nOisE imMunitY And mAy becoMe subjecT to unNEcessary drop-ouT Of the carrier dETeCT SiGNal.
IN prIor art digitAl deMOdulAtorS SuCh aS DescrIbed iN tHE aFOrementioned U.S. Pat. No. 4,311,964 EmPloyinG sampLing techniqueS for systemS WITh a data tRansMIsSIon rate much lowEr thaN the carrieR FrequencY, bit fRaming is Required, sINCe each baSebAnd DatA syMBOl, Or bit, extends oVER sevErAl carriEr sEgments. a daTa sYmbOl eXtEnds over fOur segmeNtS iN tHe AppAratuS Of U.S. Pat. NO. 4,311,964. IT is NeCesSary tO DetermIne at WhicH cArRIer Segment A DaTA SymbOl BeGins. for ExAmple, Is thE CarRier segMent curreNtlY BeinG pRoCessed aCtually the firSt Segment of a NeW daTa symbOL (Which wilL also include the next threE SegmentS), is It the Last Segment of A daTa symbOl aLSo inclUding tHe thrEe PreCEDing sEGMeNts, Or Is it a middlE SEgmEnt of A dAta sYmbol whIch also extends over ONe oR two preceding And SuccEEDiNg sEGmENts. thE ProCESs of bit framing, oR synchroniZiNG, wAs done only AFteR tHe succeSsful deTectiON of a carRier signaL by the recEiVer oF u.s. PaT. No. 4,311,964. Carrier DetectioN thereforE Was reQUiRed to OccUr earlY eNouGh to iNsure tHAt sUccesSful biT fRaming Would Be AccompliShed during the transmissiOn of thE messAge Preamble. FUrtHErmOre, the serIal eXecution of The CarRier dEteCTion aNd biT FrAmiNG funcTionS Cause duplICaTioN OF cAlculations WHICh mAy allOw sIGnificAnt eRror propagation duE To the limited prEcisON Of 8-bIt aRIthmEtIc used in some prIor ArT MIcroprocEsSor based sysTems. It woUlD Be desIrable To provIde demoDULaTOr appaRatuS anD methods tO enAbLE more raPiD bIT framiNg anD cArrier DetectIOn.
In
 to produce a reference ve ctor signa l. Th e r efe re ncevect or and phase a n glevector signals are the n app li e d to aphase  detect o rw h ich  p ro duc es asigna l o utput i ndicatingwhe th er the incom i ng  carrier s ign al has assum edthe no mi nal phase  or  therevers e d phas e to in t ur n  indic a te whet h e rthebaseband digitald at a  is a logic 1or log ic 0. T hus , i f the phas eangle vectors ig n a l  de r ived from the  incoming c a rri er isde ter m ined t o be45 . deg ree. relati ve t o the int ernall y  genera t ed coor dinate  sy ste m, a n dis  fo ll o wed by  ap has e angleve ct or si gnal h a v inga p hase  of 2 25.degree. (i ndi cati n g a  phas e rev ersa l,  or c hangeof th ebaseband digita l da ta from a  lo gi c 1  t o a l o gic 0)  th e p hase of  the in t erm ed i a t evector signal gene ra t e dat twice  the f r eq ue n cy of th einc omin g carri er s i gn al is 45 .degre e .fo r bothof  the a fo rem ent ioned phas e angl e vector  sign a ls.
This syste m  provides gen e ra l l ys atis fac tory servic e, b u t is  rat h er  co m plex.  Furt he r mo r e, in some circumst an ces th e sys tem may not e xhibit suf f i c ient noi se i m mu n ity and may be comesubject to unnecess ary d rop-outof the ca r r ier dete ctsig nal .
I n pr ior art digit a l  dem od ulators  su ch as d esc rib edinth e aforeme ntionedU. S.  P at . N o. 4, 3 11,964 e mp loy in g s ampli n g tech nique s fo rsy s tem s witha  d a t a tr an sm issi onra te mu ch l o wer  than t he carrie r f r eque nc y,  bit fr aming is requ ir ed, sinceea chbaseba n d  data sy mbol, or bit, extends o v er seve ral  carr iersegments.  Adata s ymb o l exte nds ov er fo ur  se g m entsi n  t heap paratus of U .S.  Pat.  N o. 4 ,311,96 4. It is necessary todetermine atwhi ch c a r ri ers eg m ent  a dat a symbol begins.For exampl e, is  the carri e r s eg ment cu rrently  bein g  proces sed actua lly the f ir st s e g men t of a new  data sy mbol (whi c h wil l  a lso i ncl ude th enex t thr ee seg m ent s), i s it t he  lastsegme nt  of a da ta symbol also includin g thethree  pr eceding s egm e nts , or is i t amiddle seg men t o f a d ata symbo l wh i ch  al s o ext ends over oneo rtwo p re ceding ands u c cee dingseg m ents.Theprocess of bit fr a ming, or synch roni z i ng,  wa s  don eonly after the  su cc e s sful det ec tion of a c arrier s ig n al by  the r eceive r of U. S .  P a t. No.  4,3 11, 964. Carr ier  d e tection  t he r eforewasre quired  to oc c ur e a r ly enough to ins ure t h a t suc c ess ful b it  framin g  wou ld be acco mplished du ring t he t ransm issionof  the m ess ag e preamble .  Furtherm ore,the ser ia l ex ecu tion o f th e carri er d et ect ion and b i t  f r am in g  fu ncti ons c au se d uplicatio n  of calc ula t ions wh ic h m a y  allow si g n ificant er ror  prop a g ation duet o th e  l i mited  preci son of  8-bita rit hm etic us edi n  some pri or art mi c rop ro cess or based  s yste ms . I twould be desira ble to p rovide d e m odulat ora ppar a tus an dmethods to e nable  m o re rapi d bit  framin g  an d c arr ierdet ecti o n.
In
 to_produce a_reference vector signal. The_reference vector_and_phase angle_vector_signals are then_applied to a_phase detector which produces_a signal output_indicating_whether the incoming carrier signal has assumed the nominal phase or the reversed phase_to_in turn_indicate_whether_the baseband digital data is_a logic 1 or logic_0. Thus,_if the phase angle vector signal derived from_the_incoming carrier is_determined to be 45.degree. relative to the internally generated_coordinate system, and is followed by_a phase angle_vector_signal_having a phase of_225.degree. (indicating a phase reversal, or_change of the baseband digital data_from a logic 1 to a logic_0) the phase of the intermediate_vector signal generated at twice_the frequency_of the incoming carrier signal_is 45.degree. for_both of_the aforementioned phase_angle vector signals.
This system provides generally_satisfactory service, but_is rather complex. Furthermore, in some_circumstances_the system may_not_exhibit_sufficient noise_immunity and may_become_subject to_unnecessary_drop-out of the carrier detect signal.
In_prior_art digital demodulators such as described in_the aforementioned U.S. Pat._No._4,311,964 employing sampling techniques_for systems with a data_transmission rate much lower than the_carrier frequency,_bit framing_is required, since each baseband data symbol, or bit, extends over_several carrier segments. A data symbol_extends over four segments_in the_apparatus_of U.S. Pat._No._4,311,964. It_is necessary to determine at which carrier_segment a_data symbol begins. For example, is_the carrier segment currently_being_processed actually the first segment of_a new data symbol (which will_also include the next three_segments),_is_it the last segment of_a data symbol also including the_three preceding segments,_or is it a middle segment of_a_data symbol which also extends over_one_or two preceding and succeeding segments._The_process_of bit framing, or synchronizing,_was done only after the successful_detection of a carrier signal by the receiver of_U.S. Pat. No._4,311,964. Carrier detection therefore was_required_to_occur early enough to insure that successful bit framing would_be accomplished_during the transmission_of the message preamble. Furthermore, the serial execution of the_carrier detection and bit framing functions cause_duplication of calculations which may allow significant error propagation due to_the limited precison of 8-bit arithmetic used in_some prior art microprocessor based systems. It_would be desirable to_provide_demodulator apparatus and methods to enable more_rapid_bit_framing_and carrier detection.
In