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WO1994006205A1 - Transmission par l'intermediaire d'une liaison de communication commune d'un signal module en radiofrequence et abaisse en frequence ainsi que d'un signal pilote utilise pour la conversion - Google Patents

Transmission par l'intermediaire d'une liaison de communication commune d'un signal module en radiofrequence et abaisse en frequence ainsi que d'un signal pilote utilise pour la conversion Download PDF

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Publication number
WO1994006205A1
WO1994006205A1 PCT/GB1993/001855 GB9301855W WO9406205A1 WO 1994006205 A1 WO1994006205 A1 WO 1994006205A1 GB 9301855 W GB9301855 W GB 9301855W WO 9406205 A1 WO9406205 A1 WO 9406205A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
site
modulated
conversion
frequency
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1993/001855
Other languages
English (en)
Inventor
David John Sumner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
British Telecommunications PLC
Original Assignee
British Telecommunications PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by British Telecommunications PLC filed Critical British Telecommunications PLC
Priority to EP93919491A priority Critical patent/EP0671072A1/fr
Priority to HK97101921A priority patent/HK1000409A1/xx
Priority to GB9502543A priority patent/GB2284729B/en
Publication of WO1994006205A1 publication Critical patent/WO1994006205A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
    • H04B7/2603—Arrangements for wireless physical layer control
    • H04B7/2609—Arrangements for range control, e.g. by using remote antennas
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
    • H03D3/02—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal
    • H03D3/24—Modifications of demodulators to reject or remove amplitude variations by means of locked-in oscillator circuits
    • H03D3/241—Modifications of demodulators to reject or remove amplitude variations by means of locked-in oscillator circuits the oscillator being part of a phase locked loop
    • H03D3/242—Modifications of demodulators to reject or remove amplitude variations by means of locked-in oscillator circuits the oscillator being part of a phase locked loop combined with means for controlling the frequency of a further oscillator, e.g. for negative frequency feedback or AFC

Definitions

  • This invention relates to signal transmission techniques and in particular to techniques for transferring 5 a modulated radio frequency signal from a central site to a remote transmitter by radio.
  • the remote antenna transmits a substantially identical RF signal to that transmitted by the base station antenna.
  • micro ⁇ cellular mobile radio communications networks Another use of remote antennas occurs in micro ⁇ cellular mobile radio communications networks. Normally the modulated RF signal for transmission in the micro-cell is formed at the micro-cell' s base station from baseband signals sent to it from the macro-ceil base station. If however the
  • the fully formed modulated RF signal for transmission by the remote antenna can be supplied from a central site, perhaps located at a macro-cell base station. This would allow all signalling and multiplexing equipment serving the micro-cell
  • a known technique, discussed in the paper by Fye, for transferring a modulated RF signal from a central site to a remote transmitter comprises providing an optical fibre link between the central site and the remote transmitter.
  • the link has an optical transmitter (a laser), a transmission line (an optical fibre) and a receiver (a photodiode).
  • the modulated RF signal is applied directly to the laser and amplitude modulates the optical output of the laser. This output is carried by the optical fibre to the photodiode where the RF signal is recovered from the optical carrier.
  • the bandwidth of the optical signal generated will be much greater than the bandwidth of the RF signal. For example if the RF signal has a frequency of approximately 900 MHz and a bandwidth of approximately 10 MHz the bandwidth of the optical signal will be approximately 1800 MHz.
  • this known technique for transferring a modulated RF signal from a first site to a second site is conceptually very simple and has practical advantages, the use made of the transmission capacity of the communications link is very inefficient.
  • An object of the present invention is to provide a simple method of transferring a modulated RF signal from a first site to a second site via a communications link which, at least to some extent, ameliorates the requirements placed on the communications link by prior art methods.
  • a method of transferring a modulated radio frequency signal from a first site to a second site comprising the steps of:
  • the conversion signal used at the second site must be substantially identical in frequency to that used at the first site .
  • the invention provides at the first site a reference oscillator from which is derived both the conversion signal used to downconvert the modulated RF signal, and a pilot signal.
  • the downconverted RF signal and the pilot signal are sent via the same communications link to the second site where the pilot signal is used to derive a substantially identical conversion signal to that used at the first site.
  • the frequency stability of the modulated RF signal transmitted at the second site is not affected by the frequency stability of the reference oscillator since any variation in the reference oscillator frequency will be reflected ⁇ n both the conversion signal and the pilot signal frequencies.
  • the method of the present invention may be used with an optical fibre communications link, preferably the link is provided by a free-space radio frequency transmission system such as an FM microwave system.
  • the method provides particularly efficient use of the microwave spectrum while allowing access to the known linearity and noise advantages given by FM techniques, and ensuring that a substantially identical copy of the modulated RF signal is transferred from the first site to the second site.
  • the pilot frequency is preferably selected to be of a lower frequency than the down converted radio frequency signal so that they can be readily separated in the receiver by filters.
  • the radio frequency signal typically comprises a plurality of multiplexed radio frequency channels, each channel being suitable for use in a mobile cellular radio communications system.
  • apparatus for use, at the first site, in a method according to the invention comprising: a reference oscillator, downconverting means, means for deriving a conversion signal from the reference oscillator for use with the downconverting means, means for deriving a pilot signal from the reference oscillator, and transmitting means for transmitting a RF signal.
  • apparatus for use at the second site comprising: receiving means for receiving a RF signal, generating means for generating a conversion signal from a received pilot signal, and up converting means responsive to the conversion signal.
  • Figure 1 shows a prior art system, using an optical fibre communications link
  • Figure 2 shows a prior art system using a radio frequency communications link
  • Figure ⁇ shows a first arrangement according to the present invention
  • Figure 4 shows a second arrangement according to the present invention
  • the prior art system shown in Figure 1 comprises a macrocell base station (10), a microcell base station (13) and an optical fibre communications link (12).
  • the macrocell and microcell base stations comprise respective antennas (14) and (15) and the optical fibre communications link (12) comprises a laser (16), an optical fibre (17) and a PIN photodiode (18).
  • a modulated RF signal at 900 MHz (shown schematically in Figure 1(a)) transmitted by the macrocell base station antenna (14) is sampled within the macrocell at (11) and this signal is applied directly to the laser (16) of the optical fibre communications link (12).
  • the output of the laser (16) (shown schematically in Figure 1(b)) has a modulation bandwidth of approximately 1800 MHz.
  • This laser output is carried to the PIN photodiode (18) by the optical fibre (12).
  • the 900 MHz modulated RF signal is recovered, passed to a linear power amplifier (19) and transmitted by the microcell base station antenna (15). Frequency accuracy of the retransmitted modulated RF signal is ensured because the whole of the signal transmitted by antenna (14) is used to modulate the laser (16).
  • the prior art method could, as shown in Figure 2, be used with a radio frequency communications link.
  • the communications link could comprise a microwave source (23), an amplitude modulator (24), a pair of microwave dish antennas (25), and a receiver (26).
  • the modulated RF signal fed to the amplitude modulator (24) is modulated onto a 6 GHz signal produced by the microwave source (23), and transmitted between the microwave dish antennas (25).
  • the modulated RF signal is recovered by envelope detection, amplified and supplied to the antenna (29) for retransmission.
  • the macrocell base station (30) is provided with a down converter (33), a local oscillator (34) and a divider (35).
  • the modulated 900 MHz RF signal transmitted by the macrocell base station (30) via antenna (43) is sampled at (44) and fed to the down converter (33).
  • This signal is mixed with a conversion signal from the local oscillator (34) which is at a frequency which differs from 900 MHz by at least the modulation bandwidth of the RF signal.
  • the resulting low frequency (typically -10 MHz), modulated signal is fed to the 6 GHz transmitter (36) of a FM microwave transmission system.
  • a 500 KHz pilot signal is also fed to the same transmitter (36).
  • the signal transmitted by the FM system (shown schematically in Figure 3(b)) thus has a bandwidth of typically 40 MHz; due to FM side bands. For an AM system the bandwidth would be approximately 20 MHz.
  • this signal is demodulated in the conventional manner and the 10 MHz downconverted modulated signal and 500 KHz pilot signal are passed to the microcell base station.
  • the microcell base station (32) is provided with an upconverter (40), a phase locked oscillator (39), a linear power amplifier (41) and an antenna (42).
  • the 10 MHz signal is passed directly to the upconverter (40) whereas the 500 KHz pilot is used to derive a 890 MHz conversion signal for use with the upconverter.
  • the phase locked oscillator comprises a voltage controlled oscillator (45) operating at approximately 890 MHz, a divider (35), mixer (48) and a low pass filter (47).
  • the pilot signal at 500 KHz is used by the phase locked oscillator to exactly reproduce the conversion signal used in the macrocell base station (30).
  • the pilot signal and the divided output of the oscillator are mixed at the mixer (48) and the resulting difference signal is passed, via the low pass
  • the oscillator is locked to a 500 KHz crystal, while at the microcell base station the oscillator is locked to the incoming 500 KHz pilot signal, which is derived from the same 500kHz crystal.
  • the macrocell base station (50) is provided with a multiplier (51) rather than a divider, and the local oscillator (52) is operated at the low pilot signal frequency of 500 KHz.
  • the pilot signal is supplied to the FM transmitter (36) directly from the local oscillator while the 890 MHz conversion signal for use with the downconverter is generated by the multiplier (51).
  • the microcell base station is provided with an identical multiplier (51) and the need for an oscillator at this base station is thus eliminated.
  • the 500 KHz pilot signal is simpiy passed through the multiplier (51) to generate a 890 MHz conversion signal for use with the up converter.
  • This second embodiment has the further advantage of being less susceptible to phase noise.
  • a divider could be used at the first site and a multiplier at the second site, and vice versa.
  • the base station and remote site may each be equipped with a local oscillator to provide the down conversion reference frequency and the pilot signal for transmission to the other station for the upconversion of the signal received there.
  • the pilot signal sent from the first site to the second site may be used at the second site both for up conversion of the signals received at the second site, as described above, and for the reference signal for the down conversion of the signals that the second site transmits itself.
  • the reference oscillator at the first site will then provide the reconversion reference frequency at the first site directly.
  • the reference oscillator may be located at- either the base station or the remote site, however, if the base station communicates with more than one remote site the same reference oscillator, if located at the base station, may be used for all the links.
  • This arrangement removes the need to have a local oscillator at the second site.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Transceivers (AREA)
  • Radio Relay Systems (AREA)

Abstract

L'invention concerne une procédé de transfert d'un signal modulé en radiofréquence depuis un premier site, par exemple une station de communication de base mobile et macrocelluliare vers un second site, par exemple une station de communication de base mobile et microcellulaire. Le procédé consiste à obtenir au premier site et à partir d'un oscillateur de référence, un signal de conversion ainsi qu'un signal pilote, à utiliser le signal de conversion pour abaisser le signal modulé en radiofréquence et à envoyer le signal modulé abaissé en fréquence et le signal pilote au second site par l'intermédiaire d'une liaison de communication commune. Au second site, un second signal de conversion est obtenu à partir du signal pilote et il est utilisé pour reformer le signal modulé.
PCT/GB1993/001855 1992-09-03 1993-09-02 Transmission par l'intermediaire d'une liaison de communication commune d'un signal module en radiofrequence et abaisse en frequence ainsi que d'un signal pilote utilise pour la conversion Ceased WO1994006205A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP93919491A EP0671072A1 (fr) 1992-09-03 1993-09-02 Transmission par l'intermediaire d'une liaison de communication commune d'un signal module en radiofrequence et abaisse en frequence ainsi que d'un signal pilote utilise pour la conversion
HK97101921A HK1000409A1 (en) 1992-09-03 1993-09-02 Transmission techniques
GB9502543A GB2284729B (en) 1992-09-03 1993-09-02 Transmission techniques

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP92307996 1992-09-03
EP92307996.6 1992-09-03

Publications (1)

Publication Number Publication Date
WO1994006205A1 true WO1994006205A1 (fr) 1994-03-17

Family

ID=8211476

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1993/001855 Ceased WO1994006205A1 (fr) 1992-09-03 1993-09-02 Transmission par l'intermediaire d'une liaison de communication commune d'un signal module en radiofrequence et abaisse en frequence ainsi que d'un signal pilote utilise pour la conversion

Country Status (5)

Country Link
EP (1) EP0671072A1 (fr)
GB (1) GB2284729B (fr)
HK (1) HK1000409A1 (fr)
SG (1) SG48873A1 (fr)
WO (1) WO1994006205A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001033743A1 (fr) * 1999-11-01 2001-05-10 Qualcomm Incorporated Repeteur a unites d'emetteur-recepteurs maitre et asservies

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5001757A (en) * 1989-12-22 1991-03-19 Sprague Electric Company FM stereo tone detector
EP0468688A2 (fr) * 1990-07-25 1992-01-29 AT&T Corp. Méthode et appareil pour établir des communications sans fil entre des endroits éloignés
EP0471487A1 (fr) * 1990-08-16 1992-02-19 Hughes Aircraft Company Synthétiseur de fréquence
US5109532A (en) * 1990-01-30 1992-04-28 General Instrument Corporation Elimination of phase noise and drift incident to up and down conversion in a broadcast communication system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3335024A1 (de) * 1983-09-28 1985-04-11 Philips Patentverwaltung Gmbh, 2000 Hamburg Schaltungsanordnung fuer einen empfaenger mit zwei phasenregelkreisen

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5001757A (en) * 1989-12-22 1991-03-19 Sprague Electric Company FM stereo tone detector
US5109532A (en) * 1990-01-30 1992-04-28 General Instrument Corporation Elimination of phase noise and drift incident to up and down conversion in a broadcast communication system
EP0468688A2 (fr) * 1990-07-25 1992-01-29 AT&T Corp. Méthode et appareil pour établir des communications sans fil entre des endroits éloignés
EP0471487A1 (fr) * 1990-08-16 1992-02-19 Hughes Aircraft Company Synthétiseur de fréquence

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001033743A1 (fr) * 1999-11-01 2001-05-10 Qualcomm Incorporated Repeteur a unites d'emetteur-recepteurs maitre et asservies

Also Published As

Publication number Publication date
GB2284729A (en) 1995-06-14
HK1000409A1 (en) 1998-03-20
GB2284729B (en) 1996-08-07
SG48873A1 (en) 1998-05-18
EP0671072A1 (fr) 1995-09-13
GB9502543D0 (en) 1995-03-29

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