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`Beschreibung
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`Die voriiegende Erfindung betritft ein Richtfunksy(cid:173)
`stem fur r-1unkt-zu-Mehrpunkt-Verbindungen, bei dem
`die fur die Komrnunikation zwischen einer Zentralstation
`und mehreren Teilnehmern zur Verfugung stehenden
`Frequenzkanale bedarfsweise zuteilbar sind.
`Ein solches Rich11unksystmn ist im Mikrokwellen(cid:173)
`Magazin, Vol. 10, No. 6, 1984, S. 629, 630 erwahnt Bei
`Punkt-zu-Mehrpunkt-Richtfunkverbindungen i;='!Bt sich
`demnach die Frnquenzbandausnutzung durch eim; nur
`bedarfsweise Belegung des er1orderi!cl1en Freqenz(cid:173)
`band€lS verbessern. DiE, Kornrnunikation zwischen der
`Zentralstation und den einzelnen Teiinehmem erfolgt
`entweder durch Vielfachzugritt irn Frequenzmultiplex
`(FDM/.\) ocJer durc~1 Violiact1zu1Jriff im Zeitmui1iplE,x (TO(cid:173)
`MA), wobei die Frequenzkanale oder Zeitschlitze je
`nach Bedarf der Teilnehmer zugeteilt werden.
`Aus EP O 169 713 A3 ist ein Duplex-Ubertragungs(cid:173)
`system bekannt Dabei eliolgt iediglich zwischen zwei
`Sende!Ernpfan~is-Stationen eine Sprachiibertra1iung
`entweder nur in eine Richtung (Simplex-Ubertragung)
`oder in beide R:chtungen (Duplex-Obe11ragung) gleich(cid:173)
`zei1ig. FOr eine Sirnplex-Obertra~JUrl\J wird ein LJbertra(cid:173)
`gungsl<anai zur Ve1ii.igung gestelit, der eine groBere
`Bandbreite aufweist als jedm der zwei fur eine Dupiex(cid:173)
`LJbertragung bereitgestellten LJbertragungskaniiie. Da(cid:173)
`zu werden die Datenraten der Obertragenen Signale an
`die Bandbreite der ihnen jeweils zugeordneten Obertra(cid:173)
`gungskan~1ie angepa8t.
`Bei einem aus der WO-A-93/00751 bekannten Da(cid:173)
`tenObertragur1gssystern werden die Sendesignalpegel
`so geregelt, daB sich eine optirnale Ubertragungsquali(cid:173)
`tat einstellt.
`Der Erfindung liegt die /.\ufgabe zugrunde, ein
`Richtfunksystem der eingangs genann1en Art anzuge-(cid:173)
`ben, dessen Ober1ragungskapazitat rnoglichst flexibel
`an ,fan BE)(fa;f der TE,llnet1rnBr anqepaBt w,mJen kann.
`Erfindungsgernal3 wird diese Aufgabe durch die
`Merkmale des Anspruchs 1 gelost. Vorteilhatte Weiter(cid:173)
`bildunqen der Erfindun;J gE,hen aus d,m UrneransprO(cid:173)
`chen hervor.
`Punkt-zu-Mer,rpunki Richtlunksysteme stellen eine
`kostengunstige und mi1 geringem Auiwand realisierbare
`ieitergebundenen Obertragungssyste(cid:173)
`Aiternaiive zu
`rnen dar. Dies \Jilt in besonderern Ma8e rnr neue Netz(cid:173)
`betreiber im Rahmen des Aufbaus eigener Telekommu(cid:173)
`nikat:onsinfrastrukiur.
`Ein nach der Erfindung ausgefi.ihrtes Punkt-zu-
`Mehrpunkt Richt1unksystem kann seine Ubertragungs-
`bandbreitenkapazitat an verschiedene von den einzel(cid:173)
`nen Teiinehmern geiorderte Datenubertragungsraten
`anpassen. Darn it stellt ein solches System ein trequenz(cid:173)
`okonornisches, arn Bedarf der einzelnen Teilnehrner ori-
`entiertes Obertragungsrnedium dar.
`Anhand eines In der Zeichnung dargostellten /\us(cid:173)
`iuhrun;isbe1spieis wird nun die EriinduniJ naher erliiu-
`tert.
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`Die Figur zeigt ein Frequenzkanalraster.
`Ein Punkt-zu-Mehrpunkt Richtfunksystem besteht
`aus einer Zentralstation mit einer in Azimu1richtung
`rundstrahlenden oder sektonsiert stral1lenden Antenne
`und mehreren Teilnehmern, welche rni1 Richtantennen
`ausgestattet sind. Prinzipiell weisen die Zentralstation
`und die einzelnen TeilnBhrner in bokannter Weise Hoch(cid:173)
`frnquenz--Sende/Ernpfan;is--Baugruppen,
`Urnsetrnr
`von der Hochfrequenz- in die Zwischen1requenzebene
`10 und irn Zwischenfrequenzbereich arbeitende Modulato(cid:173)
`ren und Dernodula1oren auL
`Die Modulatoren und Demodulatoren in der Zentral(cid:173)
`station sincJ so ausiJel€igt
`cJar1 Gin Zwiscr;enfmqwrnz(cid:173)
`trager rnit einer variabien Datenrate, z.B. im Bereich von
`15 64 KBit/s bis maximal 8 MBit/s, rnodulierbar bzw. demo(cid:173)
`dulierbar is1. D.h cJl,i Z€mtralstation kann - z.B. sof1warn(cid:173)
`ges1euert - jedem Teilnehmer einen Frequenzkanal zur
`VerfOgung stellen, dessen Bandbreite an die vom iewei(cid:173)
`iigen Teilnehmer geforderte Datenubertragungsrate an-
`20 gepaBt ist. Das in der Zeichnung dargestellte Frequenz(cid:173)
`kanalraster enthalt beispielhaft zwei Frequenzkanale 1
`und 5 lur eine Datenra1e von 2 MBit/s, zwei weitere Fre(cid:173)
`quenzkanaie 2 und 4 tur eine Datemate von 64 KBit/s
`und ,~inen Frequenzkanal 3 Hir eine Datenra1e von 1
`25 MBit/s. Die Lage der einzelnen Kanale relativ zu der Mit(cid:173)
`tenfrequenz fm des Obertraqungsbandes wird zweck(cid:173)
`m~iGi9erweise so organisiert, daB die Kaniile symme(cid:173)
`trisch um die Mittenfrequenz fm he rum verteilt sind (vgl.
`Figur). Die maximal rnogliche Anzar,I der den Teilner,-
`30 mern zugeordne1en Kana.le is1 durch die Kanalraste(cid:173)
`rung, den zulassigen spektralen Abstand und die kanal(cid:173)
`individuelle Da1enrate bestirnrnt.
`In der Zentralstation konnen die von den Teilneh(cid:173)
`mern getorderten Kanalbandbreiten registriert werden,
`35 damit fur jeden Teilnehrner eine von der Ubertragur1gs(cid:173)
`bandbreite abhangige TarifierunrJ moglich ist.
`Modulatoren und Demodulatoren konnen auch fur
`vmsct1ied0ne Modulationsarten (z.B. n •· PSK, n - QPS1<
`mit 11 = 1 ... 8 oder M - QAM mit M = 4 .. 256) ausgelegt
`40 werden, so dar3 Datenubertragungen mit teilnei;rnerin(cid:173)
`dlvidu,311 untmsc:hiedlich€rn MocJulationen rn6fjlich sind.
`Um en1fernungsabhangige Empfangspegeiunter(cid:173)
`schiede ausgleichen zu konnen, ist in der Zentrals1ation
`eine entsprechende Verstarkungsregeiung fur die Sen-
`45 designale vorgesehen
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`Patentanspri.iche
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`1. Richttunksystern llir Punkt-zu-Mehrpunkt Verbin-
`dungen, bei dern die fur die Kornrnunikation zwi(cid:173)
`schen einer Zentralstation und mehreren Teilneh(cid:173)
`mern zur \le1iDgung stehenden Frequenzkanale
`bedarisweise zuteilbar sind, dadurch gekerrnzeicr1-
`ne1, daf3 die Bandbreite der einzelnen Frequenzka(cid:173)
`nale (1 ... 5) auf die von den einzelnen Teilnehmern
`jeweils geforderte Datenubertragun;israte einstell(cid:173)
`bar ist.
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`Apple Exhibit 1010
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`EP O 772 923 81
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`caracterise en ce que
`l'arnpiification des signaux d'ernission est reglable
`pour permettre de compenser des dilferences de rn(cid:173)
`veau de signal de reception dependant de i'eloigne(cid:173)
`ment.
`
`3. Systeme de radiodiffusion par faisceau dirige seion
`la revendication 1,
`caracterise en ce que
`les moduiateurs et demodulateurs peuvent etre re(cid:173)
`gl{,s sur differents types de modulation.
`
`4. Systems cJe radiodiffusion par faisc:Gau diri;~{; seion
`la revendication ·;,
`caracterise en ce que
`la s1at!on rnntrai(l r{,aiiSE, uno tariiication d0p,mdant
`de ia largeur de la bands de transmission de cha(cid:173)
`que abonne.
`
`2. Richtfunksystem nach Anspruch ·1, dadurch ge(cid:173)
`kennzeichnet, daB die Verstiirkung der Sendesi(cid:173)
`gnaie regelbar ist, so daB entfernungsabhangige
`Unterschiede der Empfangssignaipegel ausgegli(cid:173)
`chen werden konnen.
`
`3. Richtfunksystem nach Anspruch 1, dadurch ge(cid:173)
`kennzeichnet, daB Modulatoren und Dmnoduiato-(cid:173)
`ren auf verschiedene Moduiationsar1en einstellbar
`sind.
`
`4. Richtfunksystem nach Ansprucl1 1, dadurch ge(cid:173)
`lwnnzeid;net, d,iB diE, Z€mtrals1ation
`nen Teiinehmer eine von der Ubertragungsband(cid:173)
`breite abhangige Tarifierung vomimmt
`
`fur ,fa, einzel(cid:173)
`
`Claims
`
`1. Microwave system for point-to-mui1ipoint links, in
`which the frequency channels which are available
`for communication between a central station and a
`plurality of subscribers can be assigned according
`to requirements, characterized in that 1he band(cid:173)
`width of the individual frequency channels (1 ... 5)
`can be adjusted to tho data transmission rate re(cid:173)
`spectively required by the individual subscribers.
`
`2. Microwave system according to Claim 1, cr1aracter-
`ized in 1ha1 the arnplification of 1he transmission sirJ-
`nals can be regulated, so that distance-dependent
`differences in the reception signal levels can bo
`cornpensated.
`
`3. Microwave system according to Claim 1, cr1aracter-
`ized in that modu!ators and den1odula1ors can be
`adJusted 10 different types of modulation.
`
`4. Microwave system according to Claim 1, character-
`ized in that the centrai station performs tanfl meter-
`infJ for thEl individual subscribers as ,l Junction of thEl
`transmission bandwidth.
`
`Revendications
`
`1. Systeme de radiodiffusion par faisceau dirige entre
`un point et piusieurs prnnts, selon lequei les canaux
`de ir0quenco dispornbles pour la communication
`entre une station centrale et plusieurs abonnes
`pouvont &1re attribu0s a la domande,
`caracterise en co que
`la largeur de bande des differents canaux de fre(cid:173)
`quence (1 ... 5) so regle sur le d0bit do donnees do
`transmission demande par chacun des abonnes.
`
`2" Systeirne do radiodiffusion par faisceau diri;i0 selon
`la revendication 1,
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`(19)
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`(12)
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`Europaisches Patentamt
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`European Patent Office
`
`Office europeen des brevets
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`EP O 774 850 B1
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`(11)
`
`EUROPEAN PATENT SPECIFICATION
`
`(45) Date of publication and mention
`of l:r,e grant of tiie paten1:
`27.10.2004 Blliietin 2004/44
`
`(21) Application number: 96118227.6
`
`(22) Date offiiing. 13.11. i 996
`
`(51) Int Ci.7: H04L 27/38, H04Q 7/38
`
`(54) Digital signal detecting method and detector
`
`Verfahren zum Erfassen eines digitalen Signais und Detektor
`
`Procede de detection d'un signal nurnerique et detecteur
`
`(84) Designated Contracting States:
`DE GB SE
`
`(56) References Cited:
`US-A- 3 497 625
`
`US-A- 5 259 000
`
`(30) Priority 16.11.1995 JP 29870795
`
`(43) Date of publication of application:
`21.05.1997 Bulletin 1997/21
`
`(73) Proprietor: NTT MOBILE COMMUNICATIONS
`NETWORK INC.
`Minato-ku, Tokyo (JP)
`
`(72) inventors:
`• Suzuki, Yasunori
`Yokohama-shi, Kanagawa (JP)
`• Kumagai, Ken
`Yokohama-shi, Kanagawa (JP}
`• Nojima, Toshia
`Yokusuka-shi, Kanagawa (JP)
`
`(74) Representative: Hoffmann, Eckart, DipL-lng.
`Patentanwalt,
`Bahnhofstrasse 103
`82166 Grafe!fing (DE)
`
`• FINES PET Al: "FULLY DIGITAL M-ARY PSK
`AND M-ARY QAM DEMODULATORS FOR LAND
`MOBILE SATELUTE COMMUNICATIONS"
`ELECTRONICS AND COMMUNICATION
`ENGINEERING JOURNAL, 110!. 3, no. 6, 1
`December 1991, pages 291-298, XP000277949
`• AGHAMOHAMMAO! A ET Al: "A NEW METHOD
`FOR PHASE SYNCHRONIZATION AND
`AUTOMATIC GAIN CONTROL OF LINEARLY
`MODULATED SIGNALS ON FREQUENCY-FLAT
`FADING CHANNELS" IEEE TRANSACTIONS ON
`COMMUNICATIONS, vol. 39, no. 1, 1 January
`1991, pages 25-29, XP000220443
`• SAMUELi H ET AL: "VLSI architectures for a
`high-speed tunable digital modulator/
`demodulator/bandpass-filter chip set" 1992
`IEEE INTERNATIONAL SYMPOSIUM ON
`CIRCUITS AND SYSTEMS (CAT.
`N0.92CH3139-3), SAN DIEGO, CA, USA, 10-13
`MAY 1992, ISBN 0-7803-0593-0, 1992:, NEW
`YORK, NY, USA, pages 1065-1068 voi.3,
`XP002069780
`• DATABASE WPI Section El, Week 9349 Derwent
`Publications Ltd., London, GB; Class U22, AN
`93-390790 XP002069781 & JP 05 291 859 A
`(HITACHI LTD)
`
`Note: Witt1in nine months from the pubiication of t!1e mention of 1he grant of the European patent, any person may give
`notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in
`a writ1en reasoned statement. It shall not be deemed 1o have been filed untii the opposi1ion fee has been paid. (Art
`99(1) European Patent Convention)
`
`Prim0d by Jouve, 75001 PARIS (FR)
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`Description
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`EP O 774 850 81
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`[00011 The present invention relates to a digital signal cJetecl:ing mett1od whid1 permits t!1e reception of signals mod(cid:173)
`ulated by different modulation schemes and send signals of various symbol transmission rates and a detector therefor.
`[00021 To realize future multimedia communications, there is a demand tor techniques of transmitting data, speech
`and images over tt1e same digital radio channel. One possible means for effec1ively trnnsmitting data, speecl1 and
`images by digital radio communication is to use symbol transmission rates and modulationidemodulat1on scl1emes
`optimum fo;· the objects to be transmitted. In the field of mobiie communication, for instance, il is to be wished t~1at ti1e
`base station offer a service of providing still pictures of television, data bank or the like, whereas the n1obiie station be
`capabie of receiving such still pictures from the base station by simple operation with simple equipment as well as
`conducting usuai voice communications. in t~1is instance, a QPSK modulation scheme is usually employed for the voice
`communication but a QAM or similar multilevel modulation scheme is needed for the transmission of still pictures
`because of ll,e necessity for transmitl!ng a larger amount of information ti,an that required fo1·the voice communication.
`This requimrnernl could b,, met by providing indeperndenl: trans;,1itlers and mce;ivers each corresponding to a par1icuiar
`modulation/demoduiation scheme as shown in Fig. 4A. in which the transmtting station is provided with a transmitter
`group 10 consisting of, for example, QAM, PSK and FSK modulating transmitters 11, 12 and 13 and the receiving
`st,il:ion is provid,,d with a rnci,ivHr group 20 consisting of QAM, PSK and FSK receiive,rs. Anothe,r met11od is common
`to the above in !he provision of the independent transmtters 11, 12 and 13 at the transmitting side but differs therefrom
`in t!1at Hie receiving station is equipped witt1 a single; receiver 21 with QAM, PSK and FSK detec1ors 22, 23 and 24
`built therein as shown in Fig. 1 B. One possibie method for providing a plurality of detHctors in the same radio as shown
`in Fig. 1 Bis to buiid therein independent detectors each designed specifically for one modulationldernoduiation scheme.
`[0003] At present, mobile communication services are allocated 800 and 1500 MHz bands bu1 cannot be switci1ed
`back and forth betweHn them. if the bands can be switched by a simple opmation with a simplEl structure, however,
`cochannel interference can be reduced by using the 800 MHz band outdoors and the 1500 MHz band indoors and in
`closed spaces through utilization of a property that the linearity of electric waves in the 1500 MHz band is higher than
`in the 800 MHz band.
`[00041 Tf1e device configuration depicted in Fi,J. 1 B ~1as a plurnlity of independent detectors buiil--in, and hence it is
`inevi1ably bulky and complex. Furthermore, in the digital radio communication for transmitting data. speech and images,
`it is hard to instantaneously switch tl1e independent detectors by dynamicaily changing t1-1e dernoduiating scheme and
`the carrier frequency. The receiver21 quadrature--demodulales the received signal, for which it is necessary lo generate
`a local oscillation signal synchronized with the carrier of the input received signal. In 1his instance, if the carrierfrequency
`of t1-1e received signai vanes from f1 to f2, f3 , and f4 with the lapse ot time as shown in Fig. 2A. the frequency of the
`local oscillation signal also needs to vary correspondingly. To meet ti1is requirement, it is general practice in ti1e prior
`art to employ such a method as shown in Fig. 2B, in which the oscillation frequency of a PLL. local oscillator 25 is
`switched by switching means 17 to f1, f2 , f3 and t4 one after another as indicated by locai osciilators 251, 252 , 253 and
`25 4, then the output from the svvilched local oscillator and ti1e input modulated signal are multiplied by an multipiier 18
`and the multiplied output is applied to a filter 19 to obtain a base band signal. The frequency switching speed in the
`F'LL local oscillator 25 is several milliseconds at the highest even by the use of a digital ioop preset type frequency
`synthesizer. With such a low response speed, it is impossible to fully respond to tt1e frequency switching during corn-
`munication,
`[0005] For example, when tile symboi transmission rate ot the received signal varies from B1 to B2 , 8 3, and B4 with
`tt1e lapse of time as s!1own in Fig. 2C, i1 is conven1ional that filters 261, 262, 263 and 264 for filtering the output frorn
`a quadrature demodulator are switched one after another by switching means 27 and 28 in response to the variation
`in the transmission rate of the received signal as depicted in Fig. 20. Since 1he filters are formed by hardware, the filler
`switching speed cannot be increased because of transient characteristics of the filters.
`[00061 US-A-5,259,000 discloses a modulator-demodulator constructed of digitai circuits that is intended to provide
`a simple, economical modulator-demodulator apparatus, wherein tvvo MODEMs are provided for G3 facsirniie and
`G2iG1 facsimile which are selectiveiy used by controlling a switch in accordance with the received signal. The functions
`of the respective facsimile modes are impiemenled by a digital signal processor, but it is assumed that different algo ..
`rithms are used for different facsimile modes and the characteristics of each function that implements a corresponding
`facsimile mode are not changed. The document also shows the use of interpolation; however, the mterpoiation is
`performed to increase Signal--to--Noise Power Ratio to thereby avoid degradation in detection when the eye--patlern is
`closed by change in transmission rate or increase the in number of values of multi-value modulation (M-ary modulation
`scheme)
`[0007] Tf1e cJocument Fines Pet al: "Fully Digital fvl-ary PSK and M-ary QAM demodulators for iand mobile satellite
`communications'' Electronics and Communication Engineering Journal, Vo!.3, No. 6, 1December1991, pages 291-298,
`XP000277949 discloses the use of an adaptive filter, and sets of coefficients ot the adaptive fiiter are predetermined
`and stored in a memory. Tt1e document also leaches U1e use of interpola1ion, but 1he purpose is tt,e sarrn, as t!1at in
`
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`US-.&.-5,259,000.
`[0008] US-A-3,497,625 relates to digital modulation and demodulation, wherein a desired one of plural types of
`modulation scheme (and dernodulation scherne) is selectively opernteci.
`[0009] Tr,e document D4 SAMUEL! H ET AL: "VLSI architectures for a high-speed tunabie digitai modulator!demod-
`uiatolibandpass filter chip set", ·J 992 IEEE INTERNATIONAL SYMPOSIUM ON CIRCUITS AND SYSTEMS (CA!: No.
`92Cf-J.'3139-3), SAN OiEGO, CA, USA, 10--1.'3 MAY 1992, ISBN 0-7803--0593--0, 1992, NEW YORK, NY. USA, pages
`1065-·J 068 vo/.3, XP002069780 relates to an all-digital multi rate modulator/demodulator of a 3-chip set, wherein in the
`first chip a double--sideband IF signal is subjected to a Hilbert transform to obtain a complex single--sideband signal,
`in the second chip the single-sideband signal is quadrature-demodulated to produce a baseband signal and in the third
`chip the baseband signal 1s decimated to effect lowpass-filtering of a selected bandwidth. The document 04 does not
`teach the use of interpolation and decimation for en~1ancin9 tirne--resolution of quadrature-demodulation.
`[001()]
`It is therefore an object of the present invention to provide a digital signal detecting method and a detector
`tl1eretor which enable digital communication equipment having a plurality of detecting means built-in to be used in
`co1,1mon to pluralities of modula1ionidHrnodulation sct1emes, local oscillation frequencie,s and symbol transmission
`rates.
`[00111 Another object of the present invention is to provide a digital signal detecting method and a detector therefor
`wt;ich am capable; of rnsponding fas1 to tt1e swil:c:t1ing of tt;;, modulation sct1emes and a c:tiange, in the, symbol trans(cid:173)
`mission rate.
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`[0012] The;se objec1s are achieved by a meti10d as cl,iimed in claim 1 and a cietedm as claimed in Glairn 20. Preferrnd
`embodiments of the invention are subje,ot-matter of the dpendent clrnms.
`[00131 A feature of the present invention is to obtain a base band signal by subjecting an AD converted received
`signal lo digital signal proce;ssing irnpie;me;nled by soflvvare.
`[00141 The digital signal detecting method according to the present invention comprises: a quadrature-demodulating
`step of per-forming a quadrature-dernodulatir1g operation of an AD converted received modulated signal; a filtering step
`of performing a filtering opera1ion of the quadrature-demodulated signal to obtain a base band signal; and a control
`step of changing at least one process variable in at least one of tl1e quadrature-demodulating step and the filtenng
`step in response to a request for· diangir;g the process variable.
`[0015] The quadrature--demodulal:ing step rnmprises: an interpolaling step of perforrning an n--poinl interpolation of
`tl1e input modulated digital signal to interpolate therein samples at n points (n being a real number equal to or greater
`than i ); a multiplying step of cornplex--multiplying the interpolation result by a iocal oscillation signal; and a decimating
`step of performing an n-point decimation of the multiplication result to decimate therefrom samples at n points The
`process variables that can be changed in the quadrature demodulation step are the frequency, amplitude and phase
`of the local oscillation signal and ti1e value of the above-mentioned n.
`[0016] The filtering step comprises a smoothing step of smoothing the result of the quadrature-den1oduiating oper(cid:173)
`ation to reduce the number of samples; and a digital filtering step of pe1forming a band-limiting operation of the result
`of tt;e smoott1ing operation. Tiie process variables in Uie band-limiting s1ep are the number of smoott1ing points and
`the characteristic of the digital filter used.
`[0017] Further, the input rnoduiated signal is gain contrniled by an automatic gain controller for input into an AD
`converter as a signal of a predeterrnined levei range.
`[00181 The above-mentioned various processes are performed by a microprocessor which decodes and executes
`programs.
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`BRIEF DESCRIFYrlON OF THE DRAWINGS
`
`[0019]
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`Fig, 1A is a block diagram scht1matically shovving an example of a digita! n1obi!e radio communication system
`employing a piurality of different modulationidemodulation schemes;
`Fig. 1 B is a block diagram schematically showing an example of a digital mobile radio communication system
`employing a receiver which contains a plurality of detectors each corresponding to one of the modulationidemod(cid:173)
`ulation schemes in Fig. 1A;
`Fig. 2A is a grnpt; st;owing varia1ions in th,, carrier frnquency of a received signal with the lapse of tirne;
`Fig. 2B is a diagram showing a conventional method for changing the locai oscillation frequency of a detector in
`response to the variations in the carrier frequency shown in r:ig. 2A;
`Fig. 2C is a graph si10wing variations in tt,e symboi transmission rate of U1e received signal wi1h tiie lapse of l:irne;
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`Fig. 2D is a diagram showing a conventional method for switching band-!imiting filters of a detector in response
`to the variations in the symbol transmission rate shovvn in Fig. 2C;
`Fig. 3 is a block diagram i!!ustrating the functional GOnfiguration of tiie detector accorciing to U1e present invention;
`Fig. 4A is a b!ock diagram illustrating a concrete examp!e of the functional construction of quadrature ciemodulating
`means 33 in Fig. 3;
`Fig. 4B is a flowchart st1owing an example of a prncedure for automatic synct1ronization of the local oscillation
`signal witl1 the input received signal;
`Fig. 5A is a diagram explanatory of r1--point interpolation processing by an FFT tedrnique;
`Fig. 5B is a diagram explanatory of a method for performing then-point interpolation processing by an interpolation
`algorithm using an m-order function;
`Fig. 5C is a diagram explanatory of a mett1od for performing the n--point interpolation processing by a mett1od of
`estimating samples to be interpolated by an interpolation algorithm;
`Fig. GA is a diagram explanatory of n-point decimation processing by a simple decimation meti1od;
`Fig. 6B is a diagram explanatory of n-point dHcimation processing by a vv<ligt1te;d substitution ,rn,thod;
`Fig. 7 is a block diagram illustrating a concrete example of the functiona! configuration of filter means 43 in F!g. 3;
`Fig. SA is a diagram explanatory of smootl1ing processing by a simple extraction metl1od;
`Fig. 8B is a block diagram st,owing an eixarnple of Hie functional configuration for· anothe,r smoott1ing scr;em1e;
`Fig. 8C is a d!agram for explaining the operation of the Fig. 88 configuration;
`Fig. 9A througr1 9H are diagrams showing tt1e states of signals occurring at respective parts of tt1e digital detector
`according to the present invention;
`Fig. 1 0A is a block diagram illustrating an example of the functional configuration for switching the oscillation
`frequency in the quadrature demodulating means 33 in Fig. 3;
`Fig. 1 OB is a b!ock diagram showing an exam pl El of the functionai configurat!on for switching the local oscillation
`frequency in the filter means 34 in Fig. 3;
`Fig. 11
`is a block diagram illustraling an example of the functional configuration for carrying out tr1is invention
`rnelhod;
`Fig. 12 is a flowchart st1owing an example of the p;·ocedure of the detecting metr1od according lo the present
`invHnlion:
`Fig. 13 is a flowchart showing an example of the digital detecting procedure;
`Fig. 14 is a diagram showing an example of the frame structure of the received signal;
`Fig. 15 is a block diagram illustraling an example of the functional configuration in which a microprocessor for use
`in the present invention is utilized for otl1er processing;
`Fig. 16 is a block diagram illustrating the functional configuration of a transceiver embodying the present invention;
`Fig. 17A is a tablH showing, by way of example, stored contents of a process variable storage part;
`Fig. 17B is a table showing, by way of example, some of other stored contents of the process variable storage
`part; and
`Fig. 17C is a table showing. by way of example, stored contents in other areas of the storagH part of Fig 17B.
`
`DESCRIPTION OF THE PREFERRED EMBODIMENT
`
`[0020]
`r.:;eferring now to Fig. 3, an embodiment of the present invention will be described below. An analog signal
`received at an input terminal 30 is provided via a band pass filte,;· (not shown) to an automatic ga!n controller 31 wt1ich
`controls, with its amplification gain, the received signal so that its amplitude varies within a fixed range. The output
`analog signal from the autornatic gain controiler 31 is converted by an AD converter 32 to a digital signai. The received
`signa! thus converted into digita! form is subjHcted to demodulating operation by quadrature demodulating means 33
`and is spectrum shaped by filtering operation by digital filter means 34, from which a demodulated digital base band
`signal is p;·ovided at an output terminal 40. The base band signal is provided to decision means 39. wherein its in(cid:173)
`phase component and quadrature component are each decided in tmms of the symbol period, and based on these
`decision results, it is determined which signal point on the IQ--diagram tl1e base band signal corresponds to. For ex--
`amp!e, in the case of a QPSK signal, it is decided vvhether its in-phase compont1nt and quadrature compone-:nt are +1
`or -1, and based on the decision results, it is determined which of four signal points on the IQ-diagram the baseband
`signai corresponds to.
`[00211
`In Fig. 3, the arithmHtic processing for th., digital signal by th., quadrature demodulating means 33 and th.,
`digital filter means '.34 is implemented by software whicl1 uses the sampling frequency, the symbol transmission rate,
`tt1e modulalion sct1eme and tt1e local oscillation frequency as arguments (variables), Control rrn,ans 35 r1as software
`for controiling the automatic gain controller 34, the quadrature dernoduiating means 33 and the digital filler means 34.
`The control means 35 controls the automatic gain controller 3: to vary its amplification gain to lirnit the amplitude
`vmiation of t!1e base bancJ s!gnal to a fixed range. The control means 35 controls arguments set in the quadrature
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`demodulating means 33 and the digital fiiter means 34 in response to ohanges in the sampling frequency, the symbol
`transmission rate and the modulation scheme of the digitized modulated signal and the local oscillation frequency, A
`keyboard or similar set!input means 36 is connected to ti1e GOntrol rneans 35, Tt1e set/input means 36 has pluralities
`of keys indicating several sampling frequencies, several symbol transmission rates and several local oscillation fre-
`quencies, respectively, and a desired parameter is input by pressing the corresponding one of the keys indicating
`several pmamelers of each category. Alterrialively, ti1e inpul means 36 is provided wilh keys each indicaling the s,im(cid:173)
`pling frequency, the symbol transmission rate and the local oscillation frequency and has a construction in which a
`desired parameter can be input by pressing the corresponding key and its numerical value can be set and input by
`manipulating ten keys. Further, the setlinput means 36 has a plurality of keys respectively indicating modulation
`schemes so that the modulation scheme ot the received signal can be input.
`[0022] As described above, t~1e digital signal processing by the quadrature demodulating means 33 and the digital
`filter means 34, which uses the sampling frequency, the symbol transmission rate, lhe modulation scheme and the
`iocai oscillation frequency as variables, can be implemented by software. By controlling the gain of ti1e automatic gain
`controlle,r 31 and thEl variablEis with l:t;e, software of l:hEl control rrn,ans 35, it is possiblEl to construct a digilal signal
`detector which performs an operation corresponding to a parameter specified in one of the groups of modulation
`schemHs, iocai oscillation frequenciHs and symbol transmission rates.
`[0023] Fig. 4A st10ws a prefemed configuration of the, quadrature dernoduiating means 33 in Fig. 3. The, outpul digital
`signai from the A.D converter 32 is subjected to an n-point inte1·polation by n-point interpolation means 41 1 and 41 0 ,
`whereby samples are inlerpolated in the digital signal al n points on the lime base. Ti1e interpolated signals are fed to
`multiplying means 42 1 and 420 , wherein they are muitipliEid by 90"-out-of-phase signals fu(k) and fLo(k)from local
`oscillation means 45. The outputs from the multiplying means 421 and 420 are subjected to an n-point decimation by
`n .. poin1 dEicimation means 431 and 430 , whereby samples are decimatEid from tr1e multiplied outputs at n points on the
`time base. By this decimation processing, the samples interpolated by then-point interpolation means 41 1 and 41 0 are
`decimated from the multiplied outputs, 'Nhereby the in-phase and quadrature components of the demodulated signal
`from the quadrature demodulation means 33 can be oblained. The time resoiution for the multiplication processing
`can be scaled up by the n-pOint interpolation means 41 1 and 41 0 . The scaied-up time resolution permits the establish(cid:173)
`ment of synchronization between the digitized modulated signals and the local oscillation signals with r1igh accuracy,
`and the time resolution of the multiplied outputs is scaled down by then-point decimation means 43i and 430 , lessening
`tl1e load of subsequent digitai signal processing. The multiplying means 421 and 420 constitute a complex multiplying
`means 42.
`[0024] A description wili be given of the arithmetic operation by the quadrature demodulating means 33. The input
`analog signal (an IF signal) y(t) to the AD converter 32 can be expressed by the foliowing equation
`
`y(t) "'A(t)cos{cot+cp(t)}
`
`(1)
`
`where tis time.mis 2:rrf (where f is the carrier frequency), A(t) is the envelope and ql(t) is the phase. The analog signal
`y(t) iS sampled by the AO converter 32 every sampling tirne T8 and eacl1 sample value is converted to a digital signal.
`Letting m denote an integer, the time t and tl1e sampling time T8 bear the foliowing relationship.
`
`