EP0562896A1 - Übertragungssteuerungsverfahren und -system eines monofregmenten und/oder FM-Sendernetzwerkes mit Überlappungszone - Google Patents

Übertragungssteuerungsverfahren und -system eines monofregmenten und/oder FM-Sendernetzwerkes mit Überlappungszone Download PDF

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Publication number
EP0562896A1
EP0562896A1 EP93400547A EP93400547A EP0562896A1 EP 0562896 A1 EP0562896 A1 EP 0562896A1 EP 93400547 A EP93400547 A EP 93400547A EP 93400547 A EP93400547 A EP 93400547A EP 0562896 A1 EP0562896 A1 EP 0562896A1
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EP
European Patent Office
Prior art keywords
frequency
transmitters
transmitter
signal
network
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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.)
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EP93400547A
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English (en)
French (fr)
Inventor
André Lascaux
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Telediffusion de France ets Public de Diffusion
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Telediffusion de France ets Public de Diffusion
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Publication of EP0562896A1 publication Critical patent/EP0562896A1/de
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/65—Arrangements characterised by transmission systems for broadcast
    • H04H20/67—Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency

Definitions

  • the invention relates to a method and a system for controlling a network of transmitters working, in frequency modulation and / or at a single final transmission frequency (single frequency network).
  • the coverage of a territory by the same program in particular in frequency modulation, for example a radio program requires several frequencies distributed between the various transmitters to allow an overlap between their emission diagrams in order to cover all the surface to be served without Gray areas. This situation is particularly detrimental for listening to a program from a mobile receiver since it is necessary to regularly adapt the frequency of the receiver according to the frequency of the nearest transmitter. Furthermore, such a solution consumes frequencies in an already highly saturated band. It is therefore useful to design a network of transmitters, in particular in frequency modulation working at the same modulation frequency. In the interference zones between the transmitters, it is desirable for such a network of transmitters that there is phase concordance for the modulating signals and / or that the HF high frequency interference is attenuated when two transmitters are received with similar field levels.
  • the invention proposes to control, possibly in synchronism, terrestrial transmitters forming part of a single frequency network and / or FM, in particular broadcasting, and supplied from a transmission medium or by satellite and which use analog transmission.
  • a monophonic LF program generated from a network head station, can frequency-modulate a subcarrier according to the same characteristics as the final broadcast before being inserted for example in an existing analog video multiplex such as than the one used by "Telecommunicationdiffusion de France” known as "MT4".
  • the analog video multiplex "MT4" comprises a video channel up to 6 MHz and several subcarriers, for example four subcarriers, (7.5; 8.5; 9.2 and 10 MHz), one or two are available for transporting the BF program.
  • the broadcasting of programs in frequency modulation clearly distinguishes two functions: the studio-transmitter transmission which ends its mission by delivering the signals in baseband and the broadcasting proper which, in each transmitter, and starting from the basic signals in low LF frequency, composes the multiplexes, frequency module (FM) and amplifies the high frequency HF signals.
  • FM frequency module
  • the subject of the invention is a method allowing phase concordance for the modulating signals of the message of a single frequency network.
  • a phasing of the low frequency modulating signals in overlap zones between transmitters, supplied by at least one satellite is carried out, according to the invention, with asymmetric emission diagrams so as to choose zones of interference where their modulations are naturally in phase to avoid the contribution of delay lines.
  • the transmitters can be available on the same terrestrial meridian.
  • said asymmetric emission diagram is such that the phasing takes into account the difference in times of arrival at the transmitters of the signal transmitted by said satellite, and the propagation time of the signals from each transmitter. towards said area.
  • the phenomena of high frequency interference between two transmitters having a zone of overlap of their emissions can be notably attenuated by implementing an amplitude modulation of the signals transmitted by at least two transmitters, by an amplitude modulation signal whose frequency is high compared to the maximum frequency of the modulating signals of the message transmitted.
  • the method implements an amplitude modulation of the signals transmitted by at least one out of two transmitters having an overlap zone, by an amplitude modulation signal whose frequency is high relative to the maximum frequency modulating signals of the message sent.
  • Amplitude modulation has a modulation rate advantageously less than 30% and preferably between 10 and 20%.
  • the invention also relates to a method for controlling a network of transmitters working in particular in frequency modulation with a single final transmission frequency and comprising a head-end transmitter for transmitting an analog multiplex including at least a first sub- carrier modulated by a low frequency LF program and transmitters at the final transmission frequency for the implementation of the above method characterized in that each transmitter is arranged to receive an unmodulated transposition frequency, of frequency lower than the final frequency of transmission and to transpose without demodulating it, the first subcarrier using the transposition frequency, to the final transmission frequency.
  • the subcarrier present in the analog video multiplex is not demodulated but it is directly transposed to the final transmission frequency of the transmitter corresponding (in the case of a plurality of frequencies) or to the final transmission frequency of the network (in the case of a single frequency network) by using (possibly after multiplication) a transposition frequency which, in the second case, is common to all transmitters and which can accompany a modulated subcarrier in a multiplex including video or which can be transmitted to transmitters through any transmission medium, for example a subcarrier taken on a video channel of a satellite or which can possibly be produced by a local oscillator of good stability, in particular for some of the transmitters, of end of rese at.
  • each transmitter of the network must for this purpose have a signal of the same frequency F2 which we call "beacon”.
  • the "beacon” can thus be transmitted to "senders on a channel parallel to the program channel.
  • it can take the form in analogical multiplexes of an additional subcarrier or a free subcarrier. It can also use a different route, the most advantageous case being as mentioned above, the distribution of this beacon by satellite. Note that this beacon can have other profitable uses such as stabilization of in the television and radio transmitters and rebroadcasters.
  • a method for controlling a network of transmitters working, in frequency modulation, at a single final transmission frequency is such that the transmitters are supplied by an analog head-end signal, in particular a multiplex analog, for example video, including at least a first subcarrier modulated by an FB program consists in using a reference signal, in particular a second unmodulated subcarrier, and of frequency lower than the transposition frequency, multiplied in each transmitter, to transpose the subcarrier modulated by the LF program to the final transmission frequency.
  • the preferred embodiment of the invention makes it possible to simultaneously fulfill these three conditions in networks where the transmitters are supplied by HF links with analog transmission (terrestrial radio-relay systems, satellite or any other HF link modulated in FM).
  • a composite signal of the analog video multiplex type including, in addition to a video signal VI (video channel VVI), modulated subcarriers (BF1 ... BF4) in frequency (channels V1 to V4) by a LF program (or by a stereo composite signal) and an unmodulated subcarrier EF2 (channel BO) of frequency F2 constitutes a headend 10 by a terrestrial network (radio beam) or by satellite to a plurality of transmitters.
  • a power transmitter (11 ... 50) of the transmission network receives from the network head 10 a composite signal SC constituted by an analog video multiplex (for example reception multiplex MT 4.R) comprising in addition the video signal SVI (“VID” channel), five subcarriers SBF1, SF0, SBF3, SBF4 and SF2 corresponding respectively to the transmission channels V1 to V4 and B0. Two of these subcarriers (F0 and F2) are used for network transmitters.
  • the composite signal SC is therefore demultiplexed by input circuits 11 of the receiver 12 to selectively obtain, thanks to a circuit comprising a filter 2 and an intermediate frequency circuit FIV2, the subcarrier SF0 (of frequency F0 for example 8.5 MHz ) frequency modulated by the program BF and thanks to a circuit comprising a filter 5 and an intermediate frequency circuit FIF2, a signal SF2 of frequency F2, for example an unmodulated subcarrier.
  • the frequency F1 is 8.5 MHz and the frequency F2 is 10.77 MHz.
  • Other circuits (1, FIV1, CBF1), (3, FIV3, CBF3), (4, FIV4, CBF4) and VID allow to obtain low frequency signals respectively SBF1, SBF3, SBF4, as well as a video signal Please.
  • Circuits 1, 3 and 4 are filters at the respective frequencies of the subcarriers, the circuits FIV1, FIV3 and FIV4 are intermediate frequency circuits, and the circuits CBF1, CBF3 and CBF4 are circuits for generating LF signals.
  • the two signals F1 and F2 feed a transposer TRA comprising a frequency multiplier 20 to produce a transposition signal FT, a signal mixer 30 and a filter 40 allowing signals to pass through at the transmission frequency (for example 105.5 MHz) which can be the final frequency sought in frequency modulation of the network.
  • a bandpass filter 40 calibrated on the transmission frequency Fx is implemented to attenuate the undesirable products created in the mixer 30.
  • the signal SFx thus obtained can enter directly into the amplifier 50 of the transmitter, or pass through a amplitude modulator MOD in the case where this function is implemented to attenuate interference dips (see below).
  • the signal supplied at the output of the mixer 30 is filtered by the filter 40 before being applied to the high frequency amplifier HFA referenced 50 which amplifies it to the desired transmission power.
  • HFA referenced 50 which amplifies it to the desired transmission power.
  • the final frequency of the transmitters is stabilized from two frequencies, coming exclusively from the head of the network. Note, however, that the frequency instability of the broadcast signal is not very harmful, since it affects all transmitters in the same way.
  • the transposition signal SFT can also be generated by a local oscillator 10 of good stability referenced 25 in particular at the end of the network if the frequency of the beacon is not available.
  • the phasing of the low frequency signals in the overlapping zones of the transmitters is carried out by an optional delay line DL referenced 15 acting on the analog program signal SF0, the delay being adjusted as a function of the relative geographic position of the transmitters.
  • two transmitters 50 km apart powered by a satellite serving as the head of the network and located on the same longitude.
  • the satellite-transmitter route is approximately 40 km shorter for the one located the most southerly, hence a travel time difference equal to 130 ⁇ s to be compensated for by delay line.
  • the signal SF0 of frequency F0 equal to 8.5 MHz in the example, if necessary crosses an analog delay line DL referenced 15, calculated as a function of the differences in the path of the signal SF0 on the transmission channels upstream of two neighboring transmitters .
  • the signal SF0 to be delayed can for the circumstance be converted to digital and then returned to analog after processing.
  • the frequency F0 can be lowered to 1 MHz and then reset to F0 provided that the same transposition generator (known per se) is used at the input and at the output of the operation.
  • the delayed signal SF0 and the signal SFT combined in the mixer 30 give at output a signal SFx of frequency Fx, here 105.5 MHz. Note that current technology allows a multiplier 20 to multiply by any value.
  • the phenomena of high frequency interference between two neighboring transmitters of any network of single frequency transmitters can be attenuated by amplitude modulation, at a low rate, the signal carrier, which, in the example described, is supplied at the output of the filter. 40, by any signal of high frequency relative to the modulating message signals, for example 100 KHz. A frequency equal to at least twice the maximum frequency of the modulating message signals is then chosen (38 kHz for a stereo broadcast).
  • the choice of the location of the receiver can resolve the anomaly, but it is not the same for a mobile.
  • the program is hatched at a rate proportional to its speed (for example 10 Hz for a speed of 120 km / h).
  • any high frequency FC signal for example inaudible modulating signal of the order of 100-120 kHz
  • FC inaudible modulating signal of the order of 100-120 kHz
  • the compensation rate can be determined in the field according to the terrain data and the requirements of the broadcaster. The compensation must be all the stronger as the troughs are pronounced.
  • the theoretical difference between the maximum field and the minimum field is 21 dB for a modulation rate of 10% and 16 dB for a modulation rate of 20%. These differences are likely to be at least partially made up by the automatic gain control circuits of the receivers.
  • the amplitude modulator comprises (see fig. 1) an OSC oscillator referenced 36, for delivering a frequency of the order of 100 kHz. This frequency makes it possible to modulate the signal SFx in the amplitude modulator AM referenced 35 with an adjustable modulation rate between 0 and 20%.
  • the output signal from the modulator 35 passes through a filter 37 also centered on the transmission frequency Fx to supply the amplifier 50 with a signal S'Fx conforming to FM broadcasting standards.
  • the distance between transmitters thus depends on the bandwidth of the program to be transmitted.
  • the power of the transmitters depends on the distances thus established.
  • An example is given in Figure 2.
  • HF interference and BF phase matching In the center O of the triangle and on the perpendicular bisectors there is HF interference and BF phase matching.
  • the program undergoes in the most unfavorable sites a loss of high frequencies with conservation of the essential of the message.
  • the intervention of the third emitter of the basic triangle has the effect of attenuating the HF interference at the center O of the triangle.
  • the 3rd transmitter improves the level differences as soon as we leave point x located on the axis connecting transmitters A and B.
  • Figure 3a represents a distribution by satellite in the most unfavorable case where the two transmitters A 'and B' of the network are 50 km apart due exclusively to a deviation in latitude.
  • the distance traveled to reach a point located 50 km north of the transmitter A ' is approximately 40 km greater. Therefore, to put these signals back in phase at the input of A 'and B', the components SF0 at the input of the transmitter A 'must be delayed by 130 microseconds. Note that for two transmitters located at the same latitude the delay becomes unnecessary, this is the most favorable case.
  • transmitters A '- B' - C ' located every 50 km on the same meridian and supplied by a geostationary satellite SAT facing south.
  • the invention proposes to establish for each transmitter radiation patterns similar to that of FIG. 3b.
  • This diagram is practically that of a panel antenna for which the front / rear difference is approximately 20 dBs.
  • the axis of fire of the antenna being directed to the North, that is to say opposite to the satellite, it follows that the critical area of overlap where the fields are equal (point R) is 45 km in front of the transmitter A 'and 5 km behind the transmitter B'.
  • the signal BF starting from the transmitter A ' covers 45 km.
  • the delay line is then unnecessary.
  • one of the transmitters A 'or B' becomes preponderant.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Radio Relay Systems (AREA)
  • Transmitters (AREA)
EP93400547A 1992-03-06 1993-03-03 Übertragungssteuerungsverfahren und -system eines monofregmenten und/oder FM-Sendernetzwerkes mit Überlappungszone Withdrawn EP0562896A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9202707A FR2688364B1 (fr) 1992-03-06 1992-03-06 Procede et systeme permettant d'obtenir un reseau d'emetteurs fm, notamment monofrequence synchrone.
FR9202707 1992-03-06

Publications (1)

Publication Number Publication Date
EP0562896A1 true EP0562896A1 (de) 1993-09-29

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EP93400547A Withdrawn EP0562896A1 (de) 1992-03-06 1993-03-03 Übertragungssteuerungsverfahren und -system eines monofregmenten und/oder FM-Sendernetzwerkes mit Überlappungszone

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EP (1) EP0562896A1 (de)
FR (1) FR2688364B1 (de)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4317220A (en) * 1979-02-05 1982-02-23 Andre Martin Simulcast transmission system
US4363129A (en) * 1980-12-11 1982-12-07 Motorola, Inc. Method and means of minimizing simulcast distortion in a receiver when using a same-frequency repeater
EP0110009A1 (de) * 1982-11-30 1984-06-13 Robert Bosch Gmbh FM-Gleichwellenfunksystem
FR2598052A1 (fr) * 1986-04-28 1987-10-30 Rottiers Roland Procede de transmission sec fm
EP0370915A1 (de) * 1988-11-23 1990-05-30 Compagnie Financiere Et Industrielle Des Autoroutes Vorrichtung und System für Gleichfrequenzfunk mit verringerten Interferenzen
US5038403A (en) * 1990-01-08 1991-08-06 Motorola, Inc. Simulcast system with minimal delay dispersion and optimal power contouring
EP0462341A1 (de) * 1989-03-21 1991-12-27 Tft, Inc. Synchronisiertes frequenzmoduliertes Verstärkersystem

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58115952A (ja) * 1981-12-29 1983-07-09 Mitsubishi Electric Corp 同期放送装置
CH667169A5 (de) * 1984-07-20 1988-09-15 Bbc Brown Boveri & Cie Verfahren zur phasenstarren uebertragung eines niederfrequenten modulationssignals sowie schaltungsanordnung zur durchfuehrung des verfahrens.
JPS6297440A (ja) * 1985-10-23 1987-05-06 Mitsubishi Electric Corp テレビジヨン同期放送装置

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4317220A (en) * 1979-02-05 1982-02-23 Andre Martin Simulcast transmission system
US4363129A (en) * 1980-12-11 1982-12-07 Motorola, Inc. Method and means of minimizing simulcast distortion in a receiver when using a same-frequency repeater
EP0110009A1 (de) * 1982-11-30 1984-06-13 Robert Bosch Gmbh FM-Gleichwellenfunksystem
FR2598052A1 (fr) * 1986-04-28 1987-10-30 Rottiers Roland Procede de transmission sec fm
EP0370915A1 (de) * 1988-11-23 1990-05-30 Compagnie Financiere Et Industrielle Des Autoroutes Vorrichtung und System für Gleichfrequenzfunk mit verringerten Interferenzen
EP0462341A1 (de) * 1989-03-21 1991-12-27 Tft, Inc. Synchronisiertes frequenzmoduliertes Verstärkersystem
US5038403A (en) * 1990-01-08 1991-08-06 Motorola, Inc. Simulcast system with minimal delay dispersion and optimal power contouring

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FR2688364A1 (fr) 1993-09-10
FR2688364B1 (fr) 1995-02-24

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