United States Patent [19]
`Auvray
`
`US005953641A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,953,641
`Sep. 14, 1999
`
`[54] MULTIMODE RADIO COMMUNICATION
`TERMINAL
`
`[75] Inventor: Gérard Auvray, Bezons, France
`
`[73] Assignee: Alcatel Mobile Phones, Paris, France
`
`[21] Appl. No.: 08/777,733
`[22]
`Filed:
`Dec. 20, 1996
`[30]
`Foreign Application Priority Data
`
`Dec. 22, 1995 [FR]
`
`France ................................. .. 95 15396
`
`[51] Int. Cl.6 ..................................................... .. H04B 1/40
`[52] US. Cl. ............................ .. 455/74; 455/86; 455/208;
`455/260; 455/553
`[58] Field of Search ................................... .. 455/552, 553,
`455/74, 75, 76, 84, 85, 86, 87, 208, 259,
`260, 264, 256, 314, 318, 323, 326; 375/298
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,259,644
`5,319,799
`5,519,885
`
`3/1981 Iimura ................................... .. 455/260
`6/1994 Morita ..................................... .. 455/86
`5/1996 Vaisanen ..
`.... .. 455/76
`
`5,564,076 10/1996 Auvray . . . . . . . . .
`
`. . . . .. 455/76
`
`5,606,736
`
`2/1997 Hasler et al. .
`
`455/260
`
`5,610,559
`
`3/1997 Dent . . . . . . . . . . . . . . . . .
`
`. . . . .. 455/76
`
`5,732,330
`5,734,970
`
`3/1998 Anderson et al. ...................... .. 455/86
`3/1998 Saito ....................................... .. 455/87
`
`FOREIGN PATENT DOCUMENTS
`
`2258776
`WO8907865
`
`2/1993 United Kingdom .
`8/1989 WIPO .
`
`OTHER PUBLICATIONS
`Weger et al, “Completely Intergrated 1.5GHz Direct Con
`version Transceiver”, 1994 Symposium on VLSI Circuits,
`Jun. 9, 1994, Honolulu, pp. 135—137.
`Primary Examiner—Nguyen Vo
`Assistant Examiner—Lester G. Kincaid
`Attorney, Agent, or Firm—Sughrue, Mion, Zinn, Macpeak
`& Seas, PLLC
`[57]
`
`ABSTRACT
`
`A multimode radio communication terminal includes a tun
`able source of transmit and/or receive local oscillator signals
`for transmitting and/or receiving channels of different fre
`quency bands in at least tWo radio communication systems.
`The terminal includes, downstream of the tunable source, a
`switchable frequency changer implementing a ?xed fre
`quency change and selectively insertable so that, the source
`responding directly to the requirements of one radio com
`munication system, insertion of the frequency changer ren
`ders it capable of responding to the requirements of another
`radio communication system using different frequency
`bands. This is achieved by virtue of a particular change to
`the frequency produced by the tunable source, effected by
`the frequency changer.
`
`6 Claims, 1 Drawing Sheet
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`U.S. Patent
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`Sep. 14, 1999
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`5,953,641
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`1
`MULTIMODE RADIO COMMUNICATION
`TERMINAL
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention concerns digital radio communica
`tions and, more particularly, a multimode radio communi
`cation terminal able to operate in at least tWo different radio
`communication systems using relatively close frequency
`bands, i.e. frequency bands that can be processed by the
`same technological means.
`2. Description of the Prior Art
`The invention may be applied in a dual mode GSM/DECT
`terminal, for eXample. The GSM system uses the frequency
`bands 890—916 MHZ and 935—960 MHZ for the tWo trans
`mission directions and the DECT system uses the frequency
`band 1880—1900 MHZ.
`In the transmitter of a radio communication terminal a
`local oscillator produces a signal at the frequency of a
`transmit channel. In the receiver of a radio communication
`terminal the local oscillator produces a signal at the fre
`quency of a receive channel. The signal at the transmit
`channel frequency, or transmit local oscillator signal, is
`modulated by the signal to be transmitted to produce a
`transmit signal. The signal at the receive channel frequency,
`or receive local oscillator frequency, is used to demodulate
`a receive signal carrying the information to be received. In
`the case of direct demodulation the receive local oscillator
`signal is combined vectorially With the receive signal picked
`up by the antenna to obtain a baseband information signal.
`In different calls a terminal must be tuned to transmit and
`receive channels that are each different each time, depending
`on the local availability of the system in Which it is used. The
`transmit and receive local oscillator signals are therefore
`provided by at least one source that can be tuned to the
`channels of the system. Since, in the digital radio commu
`nication systems discussed here, transmission takes place in
`a temporal frame With transmission and reception separated
`in time, a single tunable source is sufficient.
`In the case of a dual mode terminal, although the con
`ventional solutions require either a single tunable source
`With a much greater bandWidth or tWo separate tunable
`sources, one for each radio communication system, using a
`single tunable source of limited bandWidth has already been
`considered, as described in patent document FR-A-93 07
`775. The principle adopted is ?rstly to achieve concordance
`of the frequency bands of the tWo systems and then to tune
`the terminal to a transmit channel or a receive channel using
`a single tunable source the tuning frequency band of Which
`is more or less that of one only of the systems.
`HoWever, this requires an additional intermediate
`demodulator system in the receiver converting the receive
`band of one of the systems for concordance With the receive
`band of the other system.
`Accordingly, an object of the present invention is a
`multimode radio communication terminal including, as
`previously, a tunable source of transmit and/or receive local
`oscillator signals, for transmitting and/or receiving one of
`the channels of different frequency bands in at least tWo
`radio communication systems but that does not require any
`frequency band conversion beforehand.
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`SUMMARY OF THE INVENTION
`In accordance With the invention, this object is achieved
`because said terminal includes, doWnstream of said tunable
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`source, a sWitchable frequency changer implementing a
`?xed frequency change, selectively insertable so that, said
`source responding directly to the requirements of one radio
`communication system, insertion of said frequency changer
`renders it capable of responding to the requirements of
`another radio communication system using different fre
`quency bands, by virtue of a particular change to the
`frequency produced by said tunable source effected by said
`frequency changer.
`In one embodiment, said frequency changer divides the
`frequency of the tunable source by a particular factor. Said
`factor is 2, in particular in the case of a GSM/DECT dual
`mode terminal.
`The outputs of the tunable source and of the frequency
`changer are advantageously each folloWed by a phase-shifter
`supplying tWo signals phase-shifted 90° for modulating/
`demodulating signals of tWo radio communication systems
`applying quadrature modulation.
`Only tWo miXers are advantageously provided for
`modulating/demodulating signals of tWo radio communica
`tion systems, these miXers receiving the signals phase
`shifted 90° from one or from the other of said tWo phase
`shifters.
`The various objects and features of the invention are
`described in detail in the folloWing description of one
`embodiment of the invention given by Way of non-limiting
`eXample With reference to the accompanying draWing.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`The accompanying draWing shoWs a dual mode terminal
`in accordance With the invention.
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`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`The dual mode terminal shoWn in simpli?ed form in the
`?gure includes a keypad CLV and a display AFF associated
`With a control device CDE enabling the user of the terminal
`to control the terminal to access one of at least tWo radio
`communication systems, for eXample the Well-knoWn GSM
`and DECT systems, and to exchange signals With those
`systems to obtain radio communications. The communica
`tions can be of varied forms. There are shoWn only a
`loudspeaker HP and a microphone M for voice communi
`cations associated With a speech coder/decoder CODEC
`connected to a modulator MOD and to a demodulator
`DEMOD.
`The transmit part CE of the terminal includes, in addition
`to the modulator MOD having tWo outputs EI and EQ at
`Which baseband signals to be transmitted are obtained, tWo
`transmit miXers MEI and MEQ the outputs of Which are
`conjointly connected to a transmit ampli?er AEM, the
`output of the latter driving an antenna ANT via a dupleXer
`DUP.
`The receive part CR of the terminal includes, connected
`to the antenna ANT and the dupleXer DUP, a receive
`ampli?er ARC and tWo receive miXers MRI and MRQ
`supplying baseband receive signals to inputs RI and RQ of
`the demodulator DEMOD.
`In the transmitter part, the voice signals from the micro
`phone M, digitally encoded in the coder/decoder CODEC,
`are converted to the transmission format in the modulator
`MOD Which produces the signals to be transmitted in the
`form of successive transmit symbols each comprising tWo
`transmit unit signals respectively obtained at the outputs EI
`and EQ. In a ?rst transmit miXer MEI the transmit unit signal
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`El conditions the amplitude of a 0° phase-shift transmit local
`oscillator signal. In a second transmit mixer MEQ the
`transmit unit signal EQ conditions the amplitude of a
`transmit local oscillator signal in phase quadrature With the
`previous signal. The addition of the tWo modulated transmit
`local oscillator signals at the input of the transmit ampli?er
`AEM produces the radio signal to be transmitted (transmit
`signal).
`In the receiver part, a received radio signal (receive
`signal), after ampli?cation in the ampli?er ARC, drives the
`receive mixers MRI and MRQ identically. In a ?rst receive
`mixer MRI, the receive signal is combined With a 0°
`phase-shift receive local oscillator signal and this produces
`a receive unit signal at the input RI of the demodulator
`DEMOD. In a second receive mixer MRQ, the receive
`signal is combined With a receive local oscillator signal in
`phase quadrature With the preceding signal and this produces
`a receive unit signal at the input RQ of the demodulator
`DEMOD. The demodulator DEMOD recogniZes the sym
`bols that these unit signals constitute, demodulates them and
`supplies coded speech signals to the coder/decoder CODEC,
`Which produces sound via the loudspeaker HP. The control
`device CDE is connected to the coder/decoder CODEC to
`obtain the received signals and to control its operation.
`The above description is naturally highly schematic, but
`represents a technique that is Well knoWn in itself and is
`sufficient for an understanding of the present invention.
`The user controls the terminal by means of the display
`AFF and the keypad CLV, operating on the control device
`CDE, Where internal states generated periodically and auto
`matically in the control device CDE are at certain times in
`a state for transmission to the DECT radio communication
`system. At this time, sWitches CEI, CEQ, CRI, CRQ com
`manded by the control device CDE over links that are not
`shoWn are in the positions shoWn in the ?gure. The control
`device CDE is connected to a tunable source SYN, for
`example a digital frequency synthesiZer, and commands it to
`produce a transmit local oscillator signal of the DECT
`system. This local oscillator signal is provided at the output
`OL of the synthesiZer SYN and drives a DECT transmit
`phase-shifter DPHl Which supplies to the ?rst transmit
`mixer MEI, via a ?rst transmit sWitch CEI in the position
`shoWn, a 0° phase-shift DECT transmit local oscillator
`signal and, to the second transmit mixer MEQ, via a second
`transmit sWitch CEQ in the position shoWn, a phase quadra
`ture DECT transmit local oscillator signal. The signals to be
`transmitted thus modulate a DECT transmit local oscillator
`signal supplied directly by the tunable source SYN. Differ
`ent commands from the control device CDE enable modu
`lation of other DECT transmit local oscillator signals cor
`responding to other channels of the frequency band allocated
`to the DECT system. This frequency band extends from
`1880 MHZ through 1900 MHZ.
`In parallel With this, a bilateral link betWeen the control
`device CDE and the modulator MOD, just like the bilateral
`link betWeen the control device CDE and the coder/decoder
`CODEC, means that the encoding and the formatting of the
`signals to be transmitted conform to the rules of the DECT
`system.
`Moreover, at the time just referred to, Which is reserved
`for transmission, the terminal is not receiving. More
`generally, While the terminal is not receiving the receive part
`is disabled. One example of disabling means is shoWn by the
`receive sWitches CRI and CRQ being in the position RPR in
`Which the tWo receive mixers MRI and MRQ do not receive
`any local oscillator signal.
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`At other times, and in particular those reserved for
`reception, the terminal does not transmit. The transmit part
`is then disabled. This is shoWn in a similar Way by the fact
`that the transmit sWitches CEI and CEQ are in an additional
`position RPE in Which the tWo transmit mixers MEI and
`MEQ do not receive any local oscillator signal.
`When, in the DECT system, the terminal is to receive, the
`receive sWitches CRI and CRQ are set by the control device
`CDE in a position such that they connect the receive mixers
`MRI and MRQ to a DECT receive phase-shifter DPH3
`Which receives a DECT receive local oscillator signal gen
`erated in the synthesiZer SYN under the control of the
`control device CDE; it sends to the ?rst receive mixer MRI,
`via the ?rst receive sWitch CRI, a 0° phase-shift DECT
`receive local oscillator signal; it sends to the second receive
`mixer MRQ, via the second receive sWitch CRQ, a DECT
`receive local oscillator signal in phase quadrature. Thus the
`receive mixers MRI and MRQ can send the baseband
`receive unit signals RI and RQ to the demodulator DEMOD.
`The latter, connected by a control link to the control device
`CDE, supplies encoded signals to the coder/decoder
`CODEC Which converts them to voice signals output by the
`loudspeaker HP.
`The same dual mode terminal shoWn in the ?gure is also
`able to communicate via another radio communication sys
`tem such as the GSM. Apart from the fact that the encoding
`and formatting arrangements are adapted to this different
`system in the modulator MOD, demodulator DEMOD,
`coder/decoder CODEC, different local oscillator signals
`must be provided for transmitting and receiving the radio
`signals of the other system.
`To this end, the terminal shoWn comprises, doWnstream of
`said tunable source SYN, a sWitchable frequency changer
`DIV so that, the source being able to respond directly to the
`requirements of one radio communication system, as just
`explained, the insertion of said frequency changer renders it
`capable of responding to the requirements of another radio
`communication system, by virtue of a particular change to
`the frequency produced by said tunable source SYN brought
`about by said frequency changer DIV.
`In the example described, the frequency changer divides
`the frequency produced by the synthesiZer SYN by a par
`ticular factor, here equal to 2. It is therefore a simple
`frequency divider stage, such as a type D ?ip-?op, con
`nected to the output of the synthesiZer SYN and the output
`OL‘ of Which provides the required GSM local oscillator
`signal.
`The GSM system uses the frequency bands 890—915 MHZ
`and 935—960 MHZ, ie the overall frequency band 890—960
`MHZ.
`Using the single tunable source (the synthesiZer SYN),
`the invention provides frequencies in the band 1780—1920
`MHZ Which are divided by 2 by the divider DIV to produce
`the frequencies needed for the frequency band 890—960
`MHZ. More generally, the invention produces in the synthe
`siZer SYN frequencies of a band substantially in concor
`dance With that provided directly by the synthesiZer and
`changes these frequencies by an operation such as division,
`multiplication, addition or subtraction (simple circuits are
`available to carry out these four operations) to obtain the
`frequencies of another frequency band, or of a plurality of
`other frequency bands, in a multimode terminal. SWitching
`means (CEI, CEQ, CRI, CRQ in this example) select the
`various frequency bands.
`To be more precise, in the example described, the terminal
`is set to GSM transmission by the control device CDE Which
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`places the tWo transmission switches CEI and CEQ in a
`position such that the output OL‘ of the divider DIV con
`nected to a GSM transmit phase-shifter DPH2 supplies a 0°
`phase-shift GSM transmit local oscillator signal to the ?rst
`transmit mixer MEI and a phase quadrature GSM transmit
`local oscillator signal to the second transmit mixer MEQ.
`Transmission then takes place as previously described, but
`in the GSM system. It is suf?cient for the synthesiZer SYN,
`under the control of the control device CDE, to provide at its
`output OL a frequency tWice that Which the required GSM
`channel is to carry.
`In an entirely similar Way, a GSM receive phase-shifter
`DPH4 receiving a local oscillator signal OL‘ from the
`divider DIV connected to the receive mixers MRI and MRQ
`by the sWitches CRI and CRQ enables reception of GSM
`signals.
`There is claimed:
`1. A multimode radio communication terminal including
`only a single tunable source of transmit and receive local
`oscillator signals for transmitting and receiving channels of
`at least tWo different frequency bands in at least ?rst and
`second radio communication systems, respectively said ter
`minal comprising:
`a sWitchable frequency changer, doWnstream of said
`tunable source, for effecting a ?xed frequency change,
`Wherein the frequency changer is selectively insertable
`via a sWitch so that, upon said tunable source respond
`ing directly to the frequency band requirements of only
`said ?rst radio communication system, insertion of said
`frequency changer only by operation of said sWitch
`renders the terminal capable of responding to the
`frequency band requirements of only said second radio
`communication system by virtue of said ?xed change,
`to the frequency produced by said tunable source,
`effected by said frequency changer, so that said tunable
`source directly supplies via said sWitch ?rst local
`oscillator signals only for the channels of the frequency
`band in said ?rst radio communication system, so that
`said frequency changer supplies via said sWitch second
`local oscillator signals, of the changed frequency, only
`for the channels of the frequency band in said second
`radio communication system, and so that said ?rst and
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`second local oscillator signals are supplied only on a
`mutually exclusive basis.
`2. The multimode radio communication terminal claimed
`in claim 1, Wherein said frequency changer effects a division
`by a particular factor.
`3. The multimode radio communication terminal claimed
`in claim 2, Wherein said factor is 2.
`4. A multimode radio communication terminal including
`a tunable source of transmit and receive local oscillator
`signals for transmitting and receiving channels of different
`frequency bands in at least tWo radio communication
`systems, said terminal comprising:
`a sWitchable frequency changer, doWnstream of said
`tunable source, for effecting a ?xed frequency change,
`Wherein the frequency changer is selectively insertable
`so that upon said tunable source responding directly to
`the requirements of one radio communication system,
`insertion of said frequency changer renders the terminal
`capable of responding to the requirements of another
`radio communication system using different frequency
`bands, by virtue of a particular change to the frequency
`produced by said tunable source effected by said fre
`quency changer;
`Wherein outputs of said tunable source and of said fre
`quency changer are each folloWed by a phase-shifter
`producing tWo signals phase-shifted 90° With respect to
`one another for modulating/demodulating signals of
`tWo radio communication systems Which use quadra
`ture modulation.
`5. The multimode radio communication terminal claimed
`in claim 4, Wherein only tWo mixers are provided for
`demodulating receive signals of said tWo radio communi
`cation systems, said tWo mixers receiving, from one or the
`other of tWo of said phase-shifters, signals phase-shifted 90°
`With respect to one another.
`6. The multimode radio communication terminal claimed
`in claim 4, Wherein only tWo mixers are provided for
`modulating transmit signals of said tWo radio communica
`tion systems, said tWo mixers receiving, from one or the
`other of tWo of said phase-shifters, signals phase-shifted 90°
`With respect to one another.
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