EP0065615B1 - Uhf receiver for a traffic information radio broadcasting system - Google Patents

Uhf receiver for a traffic information radio broadcasting system Download PDF

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Publication number
EP0065615B1
EP0065615B1 EP82100826A EP82100826A EP0065615B1 EP 0065615 B1 EP0065615 B1 EP 0065615B1 EP 82100826 A EP82100826 A EP 82100826A EP 82100826 A EP82100826 A EP 82100826A EP 0065615 B1 EP0065615 B1 EP 0065615B1
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EP
European Patent Office
Prior art keywords
subcarrier
modulation
switch
output
announcement
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EP82100826A
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German (de)
French (fr)
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EP0065615A1 (en
Inventor
Norbert Dipl.-Phys. Eilers
Peter Ing. grad. Brägas
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Blaupunkt Werke GmbH
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Blaupunkt Werke GmbH
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Priority to AT82100826T priority Critical patent/ATE9413T1/en
Publication of EP0065615A1 publication Critical patent/EP0065615A1/en
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G1/00—Traffic control systems for road vehicles
    • G08G1/09—Arrangements for giving variable traffic instructions
    • G08G1/091—Traffic information broadcasting
    • G08G1/094—Hardware aspects; Signal processing or signal properties, e.g. frequency bands

Definitions

  • the invention relates to an FM receiver for a radio transmission system according to the preamble of claim 1.
  • the traffic radio stations which broadcast such messages more or less regularly, are characterized by a 57 kHz subcarrier broadcast in addition to the useful modulation, which is broadcast as the third multiple of the 19 kHz stereo pilot tone in synchronous fashion with stereo transmitters.
  • the 57 kHz subcarrier is phase locked to the pilot tone with zero crossings in the same direction.
  • This subcarrier also serves to transmit additional information - also called identifiers - which is transmitted as amplitude modulation of the subcarrier. (DBP 20 51 034)
  • the announcement identifier consists of a very narrow frequency band at 125 Hz, which modulates the subcarrier with 30% in its amplitude.
  • switching devices in the LF stage are controlled in a receiver intended for the system via a 57 kHz detector and an amplitude demodulator; be it to increase the volume during the announcement or, if the receiver is muted, to unmute it or, in the case of combined radio-cassette recorders, also to switch from cassette playback to playback of the traffic announcement when it starts and to switch back to cassette playback, when the announcement is finished.
  • Another information transmitted by the subcarrier is used to identify traffic radio areas. All VHF traffic radio stations that are located in a specific geographical area are identified by a uniform identifier - area identifier (BK). The traffic news of the stations with the same BK concern the same geographical area.
  • This area identifier is continuously modulated onto the subcarrier. It modulates the amplitude of the subcarrier by 60%.
  • the bandwidth of the individual area identifiers and their position relative to one another is selected such that an adjacent channel attenuation of greater than 15 dB results with a quality of greater than 20. 6 range identifiers have been defined within the available frequency band below the announcement identifier, whereby it is ensured that the harmonics of the identifiers fall between the other identifiers. (DBP 22 40 941)
  • the subcarrier is thus modulated with two identifiers, the BK and the DK, and outside the time of the traffic announcements only with one identifier, the BK.
  • each traffic radio station can also be assigned its own BK if the number of available BKs is sufficient for this.
  • the presence of the 57 kHz subcarrier can be used to interrupt the search only when traffic information stations are received. Since 57 kHz is the third multiple of the 19 kHz pilot tone, there is a risk that, due to non-linearities in the transmitter or receiver, harmonics of the 19 kHz pilot tone may also occur with non-traffic radio transmitters.
  • An auxiliary branch has therefore been provided in the detector for the 57 kHz subcarrier, which only releases the detector output when another detector indicates the presence of the area identifier. (DBP 25 33 946)
  • the degree of modulation of the subcarrier is measured by the area identifier and the search is only allowed to remain on the traffic radio station when the correct degree of modulation is found to be 60%.
  • This traffic radio system works in wide reception areas to full satisfaction.
  • incorrect switching was more common when evaluating the announcement identifier.
  • a modulation of the 57 kHz carrier is more often used, which can simulate an announcement identifier and thus cause incorrect switchovers in the LF stage.
  • the task is therefore to improve the recognition of the announcement identifier in the receiver.
  • the receiver in FIG. 1 receives its input signal via antenna 1 the desired station is set.
  • the transmitter user modulation can be removed from the ratio detector which closes the subsequent IF stage 3 and, in addition to the message intended for the radio subscriber, contains an amplitude-modulated 57 kHz subcarrier.
  • Via a switchover device 4, the messages just mentioned or the signals from a tape player 5 are optionally sent to the LF stage 6, to which a loudspeaker 7 is connected.
  • the switching device 4 is either controlled by hand or, when the tape recorder is switched on, is effected by a traffic radio decoder 8, which is also connected to the output of the IF stage 3.
  • the traffic radio decoder is also connected to a station search device 9 which, moreover, controls the setting of a desired station and which is started via the control unit 10.
  • the control unit can in turn be connected to the traffic radio decoder 8 for preselecting a specific traffic radio area.
  • the output signal of the IF stage 3 is examined in the detector 11 of the traffic radio decoder 8 shown in FIG. 2 for the presence of an amplitude-modulated 57 kHz subcarrier.
  • the amplitude modulation is separated from the subcarrier.
  • This modulation can consist of an area identifier BK and, in the case of a traffic announcement, additionally of an announcement identifier DK.
  • Two filters 13, 14 connected in parallel, the first with a passband that only includes the area identifiers and the latter with a passband for the announcement identifier alone, separate the two possible identifiers.
  • An announcement identification decoder 19 is connected to the output of the filter 14, which only allows the announcement identifiers DK to pass through. Its output signal is forwarded to a coincidence stage 18.
  • a BK decoder 17 which indicates the area identifier transmitted by the received traffic radio station.
  • a second control signal is emitted to the coincidence stage 18 if the preselected and the transmitted BK match.
  • the switching stage 4 receives a switching pulse in the known devices, which causes the receiver to switch through to the N F stage 6, provided the tape recorder 5 is switched via the switching stage 4 when the switching pulse is received is connected to NF level 6.
  • the known switching device 4 in the N F stages of the receiver therefore responds each time the set traffic radio station makes a traffic announcement and the combination device is switched to tape playback, or only if the set traffic radio transmitter is also assigned to the preselected traffic radio area and via an announcement is broadcast on this station.
  • the filter 13 is also connected to a measuring device 15 for the degree of modulation of the auxiliary carrier by the area identifier. As long as the measured value is above the degree of modulation specified as the desired value, a coincidence stage 16 receives a control signal from the measuring device 15. The auxiliary support is also present at a further entrance of coincidence level 16. The output signal of the coincidence stage 16 is then further processed in the transmitter search device 9 as a criterion for the presence of the 57 kHz auxiliary carrier, e.g. as a stop signal for the station search.
  • the part of the traffic radio decoder 8 described so far belongs to the prior art and is used in many traffic radio receivers.
  • this known circuit is supplemented by a further filter 22, which is parallel to the two filters 13 and 14 at the output of the demodulator 12.
  • the pass band of this filter is selected so that it encompasses both identifiers BK and DK.
  • a further measuring device 20 is connected downstream of this filter, which measures the total degree of modulation of the amplitude of the subcarrier by the area and announcement identifier, which changes in time in contrast to the degree of modulation of the subcarrier by the area identifier, as shown in FIG. 3, since the announcement identifier in contrast for area identification is not permanently available.
  • the two measuring devices 15 and 20 can be largely the same.
  • the output of the measuring device 20 is connected to an input of the coincidence stage 18 in FIG. 2. If the degree of modulation of the subcarrier increases significantly from 60% to around 90%, the measuring device 20 generates a control signal. This means that the coincidence stage 18 only passes on a control signal when the total degree of modulation of the auxiliary carrier rises significantly from the predetermined value - here 60% - in the present case by 50%.
  • the circuit further developed in accordance with the invention thus only triggers the switching device 4 when, in addition to the announcement identifier, a significant increase in the degree of modulation of the subcarrier has also been determined.
  • the degree of modulation drops again to 60%, the predetermined value, the switching device 4 is reset.
  • the switching device 4 can also be controlled solely by the control signal of the measuring device 20. This is indicated in FIG. 2 by the dashed connection between the measuring device 20 and the switching device 4.
  • FIG. 4 shows an exemplary embodiment of a measuring device 20.
  • FIG. 3 is again explained in more detail.
  • the time course of the modulation of the 57 kHz auxiliary carrier according to the prior art is indicated in FIG. 3.
  • the amplitude of the subcarrier is modulated solely by the area identifier, with a degree of modulation of 60%, ie the amplitude of the subcarrier fluctuates between 40% and 160% of its unmodulated value.
  • the announcement identifier is also switched on at the transmitter end.
  • the degree of modulation of the subcarrier amplitude by this identifier alone is 30%; the overall degree of modulation of the subcarrier thus increases from 60% to 90%, ie by 50%, and the subcarrier amplitude now fluctuates between 10% and 190% of the unmodulated value.
  • the auxiliary carrier with its amplitude modulation is filtered out from the useful modulation MPX of the transmitter by the 57 kHz detector 11.
  • the detector comprises a control amplifier 21, which ensures a constant amplitude of the subcarrier.
  • control amplifiers are known.
  • the time constant of the control amplifier is considerably greater than the period of the low modulation frequency of the subcarrier, it can be 1 s or more.
  • the output signal of the detector is demodulated in the subsequent demodulator 12, so that the entire amplitude modulation of the subcarrier is available at the output of the demodulator.
  • a low or bandpass 22 is connected to the output of the modulator 12, the upper limit frequency of which corresponds to or lies above the highest modulation frequency of the subcarrier.
  • a rectifier 23 follows this bandpass filter. Since the subcarrier is kept constant in the control amplifier 21, a special comparison between the entire modulation amplitude and the unmodulated subcarrier amplitude is no longer necessary here. The output amplitude of the rectifier 23 is uniquely assigned to the degree of modulation of the subcarrier.
  • a first threshold switch 24, a Schmitt trigger is controlled directly with the output signal of the rectifier 23, while another Schmitt trigger as the second threshold switch 26 is connected to the output of the rectifier 23 via a voltage divider 25.
  • This voltage divider comprises two resistors 27, 28, of which the resistor 27 located directly on the rectifier 23 is half the size of the second resistor 28 which is connected to ground. This results in a voltage division of 1: 2.
  • the first Schmitt trigger 24 is switched as soon as the output voltage of the rectifier 23 reaches a value which approximately corresponds to a degree of modulation of 60% of the subcarrier.
  • the second Schmitt trigger 26 which is set to the same threshold value, only responds when the voltage value associated with a degree of modulation of 90% is approximately reached at the output of the rectifier. This increase from 60 to 90% degree of modulation always occurs when the announcement identifier is switched on at the transmitter. This further voltage increase at the output of the rectifier leaves the Schmitt trigger 24 unaffected.
  • the output signals of the two Schmitt triggers 24, 26 are combined in an AND circuit 29.
  • the AND circuit 19 then supplies directly or indirectly (FIG. 2) the control signals for the known switching device 4 in the LF stage.
  • the output signal of the Schmitt trigger 24 can be used to indicate the presence of the auxiliary carrier and represents a variant of the measuring device 15 and the coincidence stage 16 of FIG. 2.
  • the indirect control of the switchover device 4 via the coincidence stage 18 proves to be advantageous if several announcement identifiers are used for different program types and these are in a frequency range that connects to the lower limit frequency of the actual radio broadcasts.

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  • Multimedia (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Circuits Of Receivers In General (AREA)
  • Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)
  • Near-Field Transmission Systems (AREA)
  • Burglar Alarm Systems (AREA)
  • Details Of Aerials (AREA)
  • Reduction Or Emphasis Of Bandwidth Of Signals (AREA)
  • Selective Calling Equipment (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

To improve reliability of recognition of an announcement recognition (AR) signal radiated by a transmitter upon broadcasting an announcement (e.g. traffic information, news, etc.), in the form of AM modulation of a 57 kHz auxiliary subcarrier, in which the subcarrier may also be modulated by other control signals, the subcarrier is filtered in the receiver, demodulated, and the degree of all modulations, regardless of frequency, on the subcarrier is sensed, and if the modulation changes significantly, for example rises from 60% modulation to 90% modulation (50% change), a switch (4) is activated which inhibits transmission of audio programs from an external source, such as a tape recorder (5), tuner tuned to another station, or the like, and reproduces the announcement being broadcast; termination of the AR signal, forming the AR modulation on the subcarrier, causes the switch to revert for reproduction of previously controlled audio information.

Description

Die Erfindung betrifft einen UKW-Empfänger für ein Rundfunkübertragungssystem gemäss Oberbegriff von Anspruch 1.The invention relates to an FM receiver for a radio transmission system according to the preamble of claim 1.

Stand der TechnikState of the art

Seit einigen Jahren werden innerhalb des deutschen UKW-Rundfunknetzes und auch in benachbarten Ländern von Zeit zu Zeit Verkehrsnachrichten ausgesendet. Die Verkehrsfunksender, die solche Nachrichten mehr oder weniger regelmässig ausstrahlen, sind durch einen zusätzlich zur Nutzmodulation ausgestrahlten 57-kHz-Hilfsträger gekennzeichnet, der bei Stereo-Sendern als dritte Vielfache des 19-kHz-Stereo-Pilottons synchron mit diesem ausgestrahlt wird. Dabei ist der 57-kHz-Hilfsträger mit dem Pilotton phasenstarr verkoppelt mit Nulldurchgängen in der gleichen Richtung. Dieser Hilfsträger dient zugleich auch zur Übertragung zusätzlicher Informationen - auch Kennungen genannt - die als Amplitudenmodulation des Hilfsträgers übertragen werden. (DBP 20 51 034)For some years now, traffic news has been broadcast within the German VHF radio network and also in neighboring countries. The traffic radio stations, which broadcast such messages more or less regularly, are characterized by a 57 kHz subcarrier broadcast in addition to the useful modulation, which is broadcast as the third multiple of the 19 kHz stereo pilot tone in synchronous fashion with stereo transmitters. The 57 kHz subcarrier is phase locked to the pilot tone with zero crossings in the same direction. This subcarrier also serves to transmit additional information - also called identifiers - which is transmitted as amplitude modulation of the subcarrier. (DBP 20 51 034)

Eine dieser Kennungen wird zusammen mit der Durchsage der Verkehrsnachricht ausgestrahlt. Sie zeigt also an, dass während ihrer Ausstrahlung über den UKW-Sender eine Nachricht zur Verkehrslage verbreitet wird und wird daher Durchsagekennung (DK) genannt. Die Durchsagekennung besteht aus einem sehr schmalen Frequenzband bei 125 Hz, welches den Hilfsträger mit 30% in seiner Amplitude moduliert.One of these identifiers is broadcast together with the announcement of the traffic message. It therefore indicates that a message about the traffic situation is being broadcast via the VHF transmitter and is therefore called an announcement identifier (DK). The announcement identifier consists of a very narrow frequency band at 125 Hz, which modulates the subcarrier with 30% in its amplitude.

Grundsätzlich können anderen Programmarten, z.B. Sportsendungen, andere Frequenzen als DK zugeordnet werden.Basically, other types of programs, e.g. Sports broadcasts, frequencies other than DK can be assigned.

Mit dieser Durchsagekennung werden in einem für das System bestimmten Empfänger über einen 57-kHz-Detektor und einen Amplituden-Demodulator Umschalteinrichtungen in der NF-Stufe gesteuert; sei es zur Anhebung der Lautstärke während der Durchsage oder, wenn der Empfänger stummgeschaltet ist, zur Aufhebung der Stummschaltung oder bei kombinierten Radio-Cassetten-Recordern auch zur Umschaltung von der Cassettenwiedergabe auf Wiedergabe der Verkehrsnachricht, wenn diese beginnt, und zur Zurückschaltung auf Cassettenwiedergabe, wenn die Durchsage beendet ist.With this announcement identifier, switching devices in the LF stage are controlled in a receiver intended for the system via a 57 kHz detector and an amplitude demodulator; be it to increase the volume during the announcement or, if the receiver is muted, to unmute it or, in the case of combined radio-cassette recorders, also to switch from cassette playback to playback of the traffic announcement when it starts and to switch back to cassette playback, when the announcement is finished.

Eine weitere vom Hilfsträger übertragene Information dient der Kennzeichnung von Verkehrsfunkbereichen. Alle UKW-Verkehrsfunksender, die in einem bestimmten geographischen Gebiet liegen, sind durch eine einheitliche Kennung - Bereichskennung (BK) - gekennzeichnet. Die Verkehrsnachrichten der Sender mit gleicher BK betreffen dasselbe geographische Gebiet. Diese Bereichskennung wird dem Hilfsträger kontinuierlich aufmoduliert. Sie moduliert die Amplitude des Hilfsträgers zu 60%. Die Bandbreite der einzelnen Bereichskennungen und deren Lage zueinander ist so gewählt, dass sich bei einer Güte von grösser 20 eine Nachbarkanaldämpfung von grösser 15 dB ergibt. Innerhalb des verfügbaren Frequenzbandes unterhalb der Durchsagekennung hat man 6 Bereichskennungen festgelegt, wobei sichergestellt ist, dass die Harmonischen der Kennungen zwischen die anderen Kennungen fallen. (DBP 22 40 941)Another information transmitted by the subcarrier is used to identify traffic radio areas. All VHF traffic radio stations that are located in a specific geographical area are identified by a uniform identifier - area identifier (BK). The traffic news of the stations with the same BK concern the same geographical area. This area identifier is continuously modulated onto the subcarrier. It modulates the amplitude of the subcarrier by 60%. The bandwidth of the individual area identifiers and their position relative to one another is selected such that an adjacent channel attenuation of greater than 15 dB results with a quality of greater than 20. 6 range identifiers have been defined within the available frequency band below the announcement identifier, whereby it is ensured that the harmonics of the identifiers fall between the other identifiers. (DBP 22 40 941)

Während einer Verkehrsdurchsage ist der Hilfsträger somit mit zwei Kennungen, der BK und der DK, moduliert, ausserhalb der Zeit der Verkehrsdurchsagen nur mit einer Kennung, der BK. Grundsätzlich kann auch jedem Verkehrsfunksender eine eigene BK zugeordnet sein, wenn die Zahl der verfügbaren BK dafür ausreicht.During a traffic announcement, the subcarrier is thus modulated with two identifiers, the BK and the DK, and outside the time of the traffic announcements only with one identifier, the BK. In principle, each traffic radio station can also be assigned its own BK if the number of available BKs is sufficient for this.

In Suchlaufempfängern kann man das Vorhandensein des 57-kHz-Hilfsträgers dazu ausnutzen, den Suchlauf nur bei dem Empfang von Verkehrsfunksendern zu unterbrechen. Da 57 kHz die dritte Vielfache des 19-kHz-Pilottons ist, besteht die Gefahr, dass infolge von Nichtlinearitäten im Sender oder Empfänger Oberwellen des 19-kHz-Pilottons auch bei Nichtverkehrsfunksendern entstehen. Daher hat man in dem Detektor für den 57-kHz-Hilfsträger einen Hilfszweig vorgesehen, der den Detektorausgang erst freigibt, wenn ein weiterer Detektor das Vorhandensein der Bereichskennung anzeigt. (DBP 25 33 946)In search receivers, the presence of the 57 kHz subcarrier can be used to interrupt the search only when traffic information stations are received. Since 57 kHz is the third multiple of the 19 kHz pilot tone, there is a risk that, due to non-linearities in the transmitter or receiver, harmonics of the 19 kHz pilot tone may also occur with non-traffic radio transmitters. An auxiliary branch has therefore been provided in the detector for the 57 kHz subcarrier, which only releases the detector output when another detector indicates the presence of the area identifier. (DBP 25 33 946)

In einer neueren Schaltung wird der Modulationsgrad des Hilfsträgers durch die Bereichskennung gemessen und erst bei Feststellung des richtigen Modulationsgrades von 60% das Verweilen des Suchlaufs auf dem Verkehrsfunksender freigegeben.In a newer circuit, the degree of modulation of the subcarrier is measured by the area identifier and the search is only allowed to remain on the traffic radio station when the correct degree of modulation is found to be 60%.

Dieses Verkehrsfunksystem arbeitet in weiten Empfangsbereichen zur vollen Zufriedenheit. Doch zeigten sich unter erschwerten Empfangsbedingungen häufiger Fehlschaltungen bei der Auswertung der Durchsagekennung. So tritt z.B. durch Mehrwegeempfang öfter eine Modulation des 57-kHz-Trägers auf, die eine Durchsagekennung vortäuschen kann und damit falsche Umschaltungen in der NF-Stufe bewirkt.This traffic radio system works in wide reception areas to full satisfaction. However, under difficult reception conditions, incorrect switching was more common when evaluating the announcement identifier. For example, due to multipath reception, a modulation of the 57 kHz carrier is more often used, which can simulate an announcement identifier and thus cause incorrect switchovers in the LF stage.

Aufgabe und LösungTask and solution

Es stellt sich daher die Aufgabe, die Erkennung der Durchsagekennung im Empfänger zu verbessern.The task is therefore to improve the recognition of the announcement identifier in the receiver.

Diese Aufgabe lässt sich mit den im Kennzeichen des Anspruchs 1 angegebenen Mitteln lösen, mit besonderen Vorteilen, wenn man die Mittel entsprechend den in den weiteren Ansprüchen angegebenen Merkmalen weiterbildet.This object can be achieved with the means specified in the characterizing part of claim 1, with particular advantages if the means are developed in accordance with the features specified in the further claims.

Beschreibungdescription

Anhand der Zeichnung wird die Erfindung näher erläutert. Es zeigen

  • Fig. 1 ein Blockschaltbild eines UKW-Empfängers,
  • Fig. 2 ein Blockschaltbild des Verkehrsdecoders in einem UKW-Empfänger,
  • Fig. 3 den zeitlichen Verlauf des Modulationsgrades des Hilfsträgers nach dem Stand der Technik,
  • Fig. 4 eine Messeinrichtung für einen Verkehrsfunkdecoder nach Fig. 2 zur Auswertung des gesamten Modulationsgrades.
The invention is explained in more detail with reference to the drawing. Show it
  • 1 is a block diagram of an FM receiver,
  • 2 is a block diagram of the traffic decoder in an FM receiver,
  • 3 shows the time course of the degree of modulation of the auxiliary carrier according to the prior art,
  • FIG. 4 shows a measuring device for a traffic radio decoder according to FIG. 2 for evaluating the entire degree of modulation.

Der Empfänger in Fig. 1 erhält sein Eingangssignal über die Antenne 1. In der HF-Stufe 2 lässt sich der gewünschte Sender einstellen. An dem die nachfolgende ZF-Stufe 3 abschliessenden Ratio-Detektor ist die Sendernutzmodulation abnehmbar, die neben der für den Rundfunkteilnehmer bestimmten Nachricht einen amplitudenmodulierten 57-kHz-Hilfsträger enthält. Über eine Umschalteinrichtung 4 werden wahlweise die eben erwähnten Nachrichten oder die Signale eines Tonbandwiedergabegerätes 5 auf die NF-Stufe 6 gegeben, an die ein Lautsprecher 7 angeschlossen ist.The receiver in FIG. 1 receives its input signal via antenna 1 the desired station is set. The transmitter user modulation can be removed from the ratio detector which closes the subsequent IF stage 3 and, in addition to the message intended for the radio subscriber, contains an amplitude-modulated 57 kHz subcarrier. Via a switchover device 4, the messages just mentioned or the signals from a tape player 5 are optionally sent to the LF stage 6, to which a loudspeaker 7 is connected.

Die Steuerung der Umschalteinrichtung 4 erfolgt entweder willkürlich von Hand oder wird bei eingeschaltetem Tonbandgerät von einem Verkehrsfunkdecoder 8 bewirkt, der ebenfalls an den Ausgang der ZF-Stufe 3 angeschlossen ist. Der Verkehrsfunkdecoder ist überdies mit einer Sendersuchlaufeinrichtung 9 verbunden, die im übrigen die Einstellung eines gewünschten Senders steuert und die über das Bedienteil 10 gestartet wird. Das Bedienteil kann wiederum mit dem Verkehrsfunkdecoder 8 zur Vorwahl eines bestimmten Verkehrsfunkbereiches verbunden werden.The switching device 4 is either controlled by hand or, when the tape recorder is switched on, is effected by a traffic radio decoder 8, which is also connected to the output of the IF stage 3. The traffic radio decoder is also connected to a station search device 9 which, moreover, controls the setting of a desired station and which is started via the control unit 10. The control unit can in turn be connected to the traffic radio decoder 8 for preselecting a specific traffic radio area.

Das Ausgangssignal der ZF-Stufe 3 wird in dem Detektor 11 des in Fig. 2 dargestellten Verkehrsfunkdecoders 8 auf das Vorhandensein eines amplitudenmodulierten 57-kHz-Hilfsträgers untersucht. In dem Demodulator 12 wird die Amplitudenmodulation vom Hilfsträger getrennt. Diese Modulation kann aus einer Bereichskennung BK und bei einer Verkehrsdurchsage zusätzlich auseiner Durchsagekennung DK bestehen.The output signal of the IF stage 3 is examined in the detector 11 of the traffic radio decoder 8 shown in FIG. 2 for the presence of an amplitude-modulated 57 kHz subcarrier. In the demodulator 12, the amplitude modulation is separated from the subcarrier. This modulation can consist of an area identifier BK and, in the case of a traffic announcement, additionally of an announcement identifier DK.

Zwei parallel geschaltete Filter 13, 14, ersteres mit einem Durchlassbereich, der nur die Bereichskennungen umfasst, und letzteres mit einem Durchlassbereich für die Durchsagekennung allein, trennen die beiden möglichen Kennungen.Two filters 13, 14 connected in parallel, the first with a passband that only includes the area identifiers and the latter with a passband for the announcement identifier alone, separate the two possible identifiers.

An dem Ausgang des Filters 14, das nur die Durchsagekennungen DK durchlässt, ist ein Durchsagekennungsdecoder 19 angeschlossen. Dessen Ausgangssignal wird zu einer Koinzidenzstufe 18 weitergeleitet.An announcement identification decoder 19 is connected to the output of the filter 14, which only allows the announcement identifiers DK to pass through. Its output signal is forwarded to a coincidence stage 18.

An dem Ausgang des Filters 13 liegt ein BK-Decoder 17, der die von dem empfangenen Verkehrsfunksender übermittelte Bereichskennung anzeigt. Für den Fall, dass über das Bedienteil 10 ein bestimmter Verkehrsfunkbereich vorgewählt ist - gestrichelt dargestellt -, wird ein zweites Steuersignal an die Koinzidenzstufe 18 abgegeben, wenn die vorgewählte und die übermittelte BK übereinstimmen.At the output of the filter 13 there is a BK decoder 17 which indicates the area identifier transmitted by the received traffic radio station. In the event that a certain traffic radio area is preselected via the control unit 10 - shown in dashed lines - a second control signal is emitted to the coincidence stage 18 if the preselected and the transmitted BK match.

Wenn an den Eingängen der Koinzidenzstufe 18 gleichzeitig ein Signal anliegt, erhält die Umschaltstufe 4 in den bekannten Geräten einen Schaltimpuls, welcher die Durchschaltung des Empfängers auf die N F-Stufe 6 bewirkt, sofern bei dem Empfang des Schaltimpulses das Tonbandgerät 5 über die Umschaltstufe 4 mit der NF-Stufe 6 verbunden ist.If a signal is present at the inputs of the coincidence stage 18, the switching stage 4 receives a switching pulse in the known devices, which causes the receiver to switch through to the N F stage 6, provided the tape recorder 5 is switched via the switching stage 4 when the switching pulse is received is connected to NF level 6.

Die bekannte Umschalteinrichtung 4 in den N F-Stufen des Empfängers spricht mithin jedesmal dann an, wenn der eingestellte Verkehrsfunksender eine Verkehrsfunkdurchsage durchgibt und das Kombinationsgerät auf Tonbandwiedergabe geschaltet ist, bzw. nur dann, wenn der eingestellte Verkehrsfunksender auch dem vorgewählten Verkehrsfunkbereich zugeordnet ist und über diesen Sender eine Durchsage verbreitet wird.The known switching device 4 in the N F stages of the receiver therefore responds each time the set traffic radio station makes a traffic announcement and the combination device is switched to tape playback, or only if the set traffic radio transmitter is also assigned to the preselected traffic radio area and via an announcement is broadcast on this station.

Das Filter 13 ist ausserdem mit einer Messeinrichtung 15 für den Modulationsgrad des Hilfsträgers durch die Bereichskennung verbunden. Solange der Messwert über dem als Sollwert vorgegebenen Modulationsgrad liegt, erhält eine Koinzidenzstufe 16 von der Messeinrichtung 15 ein Steuersignal. An einem weiteren Eingang der Koinzidenzstufe 16 liegt zugleich auch der Hilfsträger an. Das Ausgangssignal der Koinzidenzstufe 16 wird dann in der Sendersuchlaufeinrichtung 9 als Kriterium für das Vorhandensein des 57-kHz-Hilfsträgers weiterverarbeitet, z.B. als Stoppsignal für den Sendersuchlauf.The filter 13 is also connected to a measuring device 15 for the degree of modulation of the auxiliary carrier by the area identifier. As long as the measured value is above the degree of modulation specified as the desired value, a coincidence stage 16 receives a control signal from the measuring device 15. The auxiliary support is also present at a further entrance of coincidence level 16. The output signal of the coincidence stage 16 is then further processed in the transmitter search device 9 as a criterion for the presence of the 57 kHz auxiliary carrier, e.g. as a stop signal for the station search.

Der bis hierher beschriebene Teil des Verkehrsfunkdecoders 8 gehört zum Stand der Technik und wird in vielen Verkehrsfunkempfängern verwendet.The part of the traffic radio decoder 8 described so far belongs to the prior art and is used in many traffic radio receivers.

Gemäss einem Ausführungsbeispiel der Erfindung ist diese bekannte Schaltung ergänzt durch ein weiteres Filter 22, das parallel zu den beiden Filtern 13 und 14 am Ausgang des Demodulators 12liegt. Der Durchlassbereich dieses Filters ist so gewählt, dass er beide Kennungen BK und DK umfasst. Diesem Filter ist eine weitere Messeinrichtung 20 nachgeschaltet, die den gesamten Modulationsgrad der Amplitude des Hilfsträgers durch die Bereichs- und Durchsagekennung misst, der sich im Gegensatz zum Modulationsgrad des Hilfsträgers durch die Bereichskennung zeitlich ändert, wie Fig. 3 zeigt, da die Durchsagekennung im Gegensatz zur Bereichskennung nicht dauernd vorhanden ist.According to an embodiment of the invention, this known circuit is supplemented by a further filter 22, which is parallel to the two filters 13 and 14 at the output of the demodulator 12. The pass band of this filter is selected so that it encompasses both identifiers BK and DK. A further measuring device 20 is connected downstream of this filter, which measures the total degree of modulation of the amplitude of the subcarrier by the area and announcement identifier, which changes in time in contrast to the degree of modulation of the subcarrier by the area identifier, as shown in FIG. 3, since the announcement identifier in contrast for area identification is not permanently available.

Im Aufbau können sich die beiden Messeinrichtungen 15 und 20 in weiten Zügen gleichen. Der Ausgang der Messeinrichtung 20 ist in Fig. 2 mit einem Eingang der Koinzidenzstufe 18 verbunden. Wenn der Modulationsgrad des Hilfsträgers von 60% auf rund 90% signifikant ansteigt, erzeugt die Messeinrichtung 20 ein Steuersignal. Dies bewirkt, dass die Koinzidenzstufe 18 erst dann ein Steuersignal weitergibt, wenn der Gesamtmodulationsgrad des Hilfsträgers von dem vorgegebenen Wert - hier 60% - signifikant ansteigt, im vorliegenden Fall um 50%.In construction, the two measuring devices 15 and 20 can be largely the same. The output of the measuring device 20 is connected to an input of the coincidence stage 18 in FIG. 2. If the degree of modulation of the subcarrier increases significantly from 60% to around 90%, the measuring device 20 generates a control signal. This means that the coincidence stage 18 only passes on a control signal when the total degree of modulation of the auxiliary carrier rises significantly from the predetermined value - here 60% - in the present case by 50%.

Die entsprechend der Erfindung weitergebildete Schaltung bringt somit die Umschalteinrichtung 4 erst dann zum Ansprechen, wenn neben der Durchsagekennung auch ein signifikanter Anstieg des Modulationsgrades des Hilfsträgers festgestellt worden ist. Wenn der Modulationsgrad wieder auf 60%, den vorgegebenen Wert, abfällt, wird die Umschalteinrichtung 4 wieder zurückgestellt.The circuit further developed in accordance with the invention thus only triggers the switching device 4 when, in addition to the announcement identifier, a significant increase in the degree of modulation of the subcarrier has also been determined. When the degree of modulation drops again to 60%, the predetermined value, the switching device 4 is reset.

In einfacheren Geräten kann auch die Umschalteinrichtung 4 allein durch das Steuersignal der Messeinrichtung 20 gesteuert werden. Dies ist in Fig. 2 durch die gestrichelte Verbindung zwischen der Messeinrichtung 20 und der Umschalteinrichtung 4 angedeutet.In simpler devices, the switching device 4 can also be controlled solely by the control signal of the measuring device 20. This is indicated in FIG. 2 by the dashed connection between the measuring device 20 and the switching device 4.

In der Fig. 4 ist ein Ausführungsbeispiel für eine Messeinrichtung 20 dargestellt. Zu deren besserem Verständnis sei nochmals die Fig. 3 ausführlicher erläutert.4 shows an exemplary embodiment of a measuring device 20. For a better understanding, FIG. 3 is again explained in more detail.

In Fig. 3 ist der zeitliche Verlauf der Modulation des 57-kHz-Hilfsträgers nach dem Stand der Technik angedeutet. Vor dem Zeitpunkt ta, dem Beginn der Durchsage, wird die Amplitude des Hilfsträgers allein von der Bereichskennung moduliert, und zwar mit einem Modulationsgrad von 60%, d.h. die Amplitude des Hilfsträgers schwankt zwischen 40% und 160% ihres unmodulierten Wertes.The time course of the modulation of the 57 kHz auxiliary carrier according to the prior art is indicated in FIG. 3. Before the time t a , the beginning of the announcement, the amplitude of the subcarrier is modulated solely by the area identifier, with a degree of modulation of 60%, ie the amplitude of the subcarrier fluctuates between 40% and 160% of its unmodulated value.

Zum Zeitpunkt to wird senderseitig zusätzlich die Durchsagekennung eingeschaltet. Der Modulationsgrad der Hilfsträgeramplitude durch diese Kennung allein beträgt 30%; der Gesamtmodulationsgrad des Hilfsträgers nimmt somit von 60% auf90%zu, d.h. um 50%, und die Hilfsträgeramplitude schwankt nunmehr zwischen 10% und 190% des unmodulierten Wertes.At time t o , the announcement identifier is also switched on at the transmitter end. The degree of modulation of the subcarrier amplitude by this identifier alone is 30%; the overall degree of modulation of the subcarrier thus increases from 60% to 90%, ie by 50%, and the subcarrier amplitude now fluctuates between 10% and 190% of the unmodulated value.

In der Messeinrichtung nach Fig. 4 wird aus der Nutzmodulation MPX des Senders durch den 57- kHz-Detektor 11 der Hilfsträger mit seiner Amplitudenmodulation ausgefiltert. Der Detektor umfasst einen Regelverstärker 21, der für eine Konstanz der Amplitude des Hilfsträgers sorgt. Solche Regelverstärker sind bekannt. Die Zeitkonstante des Regelverstärkers ist erheblich grösser als die Periodendauer der niedrigen Modulationsfrequenz des Hilfsträgers, sie kann 1 s oder mehr betragen. In dem nachfolgenden Demodulator 12 wird das Ausgangssignal des Detektors demoduliert, so dass am Ausgang des Demodulators die gesamte Amplitudenmodulation des Hilfsträgers verfügbar ist.In the measuring device according to FIG. 4, the auxiliary carrier with its amplitude modulation is filtered out from the useful modulation MPX of the transmitter by the 57 kHz detector 11. The detector comprises a control amplifier 21, which ensures a constant amplitude of the subcarrier. Such control amplifiers are known. The time constant of the control amplifier is considerably greater than the period of the low modulation frequency of the subcarrier, it can be 1 s or more. The output signal of the detector is demodulated in the subsequent demodulator 12, so that the entire amplitude modulation of the subcarrier is available at the output of the demodulator.

An den Ausgang des Modulators 12 ist ein Tief-oder Bandpass 22 angeschlossen, dessen obere Grenzfrequenz der höchsten Modulationsfrequenz des Hilfsträgers entspricht oder darüber liegt. Diesem Bandpass folgt ein Gleichrichter 23. Da der Hilfsträger in dem Regelverstärker 21 konstant gehalten wird, ist ein besonderer Vergleich zwischen der gesamten Modulationsamplitude und der unmodulierten Hilfsträgeramplitude hier nicht mehr erforderlich. Die Ausgangsamplitude des Gleichrichters 23 ist dem Modulationsgrad des Hilfsträgers eindeutig zugeordnet. Mit dem Ausgangssignal des Gleichrichters 23 wird ein erster Schwellwertschalter 24, ein Schmitt-Trigger, direkt gesteuert, während ein anderer Schmitt-Trigger als zweiter Schwellwertschalter 26 über einen Spannungsteiler 25 an den Ausgang des Gleichrichters 23 angeschlossen ist.A low or bandpass 22 is connected to the output of the modulator 12, the upper limit frequency of which corresponds to or lies above the highest modulation frequency of the subcarrier. A rectifier 23 follows this bandpass filter. Since the subcarrier is kept constant in the control amplifier 21, a special comparison between the entire modulation amplitude and the unmodulated subcarrier amplitude is no longer necessary here. The output amplitude of the rectifier 23 is uniquely assigned to the degree of modulation of the subcarrier. A first threshold switch 24, a Schmitt trigger, is controlled directly with the output signal of the rectifier 23, while another Schmitt trigger as the second threshold switch 26 is connected to the output of the rectifier 23 via a voltage divider 25.

Dieser Spannungsteiler umfasst zwei Widerstände 27, 28, von denen der direkt am Gleichrichter 23 liegende Widerstand 27 halb so gross ist wie der nach Masse geführte zweite Widerstand 28. Hierdurch ergibt sich eine Spannungsteilung von 1:2.This voltage divider comprises two resistors 27, 28, of which the resistor 27 located directly on the rectifier 23 is half the size of the second resistor 28 which is connected to ground. This results in a voltage division of 1: 2.

Der erste Schmitt-Trigger 24 wird geschaltet, sobald die Ausgangsspannung des Gleichrichters 23 einen Wert erreicht, der einem Modulationsgrad von 60% des Hilfsträgers in etwa entspricht.The first Schmitt trigger 24 is switched as soon as the output voltage of the rectifier 23 reaches a value which approximately corresponds to a degree of modulation of 60% of the subcarrier.

Der zweite, auf den gleichen Schwellwert eingestellte Schmitt-Trigger 26 spricht erst dann an, wenn der einem Modulationsgrad von 90% zugeordnete Spannungswert am Ausgang des Gleichrichters in etwa erreicht wird. Dieser Anstieg von 60 auf 90% Modulationsgrad tritt beim senderseitigen Einschalten der Durchsagekennung stets auf. Dieser weitere Spannungsanstieg am Ausgang des Gleichrichters lässt den Schmitt-Trigger 24 unbeeinflusst. Die Ausgangssignale der beiden Schmitt-Trigger 24, 26 sind in einer UND-Schaltung 29 zusammengefasst. Die UND-Schaltung 19 liefert dann direkt oder mittelbar (Fig. 2) die Steuersignale für die bekannte Umschalteinrichtung 4 in der NF-Stufe.The second Schmitt trigger 26, which is set to the same threshold value, only responds when the voltage value associated with a degree of modulation of 90% is approximately reached at the output of the rectifier. This increase from 60 to 90% degree of modulation always occurs when the announcement identifier is switched on at the transmitter. This further voltage increase at the output of the rectifier leaves the Schmitt trigger 24 unaffected. The output signals of the two Schmitt triggers 24, 26 are combined in an AND circuit 29. The AND circuit 19 then supplies directly or indirectly (FIG. 2) the control signals for the known switching device 4 in the LF stage.

Mit Hilfe dieser Schaltung wird ein Steuersignal gewonnen, wenn der Modulationsgrad des Hilfs- . träger durch die BK von dem vorgegebenen Wert,

  • - hier 60%-aus noch signifikant ansteigt und wieder abfällt.
With the help of this circuit, a control signal is obtained when the degree of modulation of the auxiliary. carrier by the BK of the specified value,
  • - here 60% - increases significantly and decreases again.

Das Ausgangssignal des Schmitt-Triggers 24 kann zur Anzeige des Vorhandenseins des H ilfsträgers genutzt werden und stellt eine Variante der Messeinrichtung 15 und der Koinzidenzstufe 16 der Fig. 2 dar.The output signal of the Schmitt trigger 24 can be used to indicate the presence of the auxiliary carrier and represents a variant of the measuring device 15 and the coincidence stage 16 of FIG. 2.

Die mittelbare Steuerung der Umschalteinrichtung 4 über die Koinzidenzstufe 18 erweist sich als vorteilhaft, wenn mehrere Durchsagekennungen für verschiedene Programmarten benutzt werden und diese in einem Frequenzbereich liegen, der an die untere Grenzfrequenz der eigentlichen Rundfunksendungen anschliesst.The indirect control of the switchover device 4 via the coincidence stage 18 proves to be advantageous if several announcement identifiers are used for different program types and these are in a frequency range that connects to the lower limit frequency of the actual radio broadcasts.

Claims (6)

1. VHF receiver, intended for a broadcast transmission system, having a frequency demodulator for the transmitter signals, a detector (11 ) for an amplitude-modulated 57 kHz subcarrier contained in the transmitter signal and an amplitude modulator (12) for the 57 kHz subcarrier, additionally provided with switch-over devices (4) within the LF stage which devices are controllable by the amplitude modulation of the subcarrier and having a device (15) for the degree up to which the subcarrier is modulated by a predetermined frequency range within the modulation of the subcarrier, characterised in that a second measuring device (20) covers the total range of amplitude modulation of the subcarrier and, with a significant rise in total modulation percentage from a predetermined value to a higher modulation percentage and for its duration, triggers a control signal for the switch-over device (4) in the LF stage.
2. A VHF receiver according to Claim 1, characterised in that the second measuring device (20) triggers a control signal when the modulation percentage rises by essentially 50% of the predetermined value.
3. A VHF receiver according to Claim 2, characterised in that the second measuring device (20) triggers a control signal when the modulation percentage rises from 60 to 90%.
4. A VH F receiver according to Claim 1, 2 or 3, characterised in that the detector (11) for the subcarrier is followed by an AGC amplifier (21) and the latter is followed by a filter (22) the band width of which covers the total frequency range of the amplitude modulation of the subcarrier, that the subsequent measuring device comprises a rectifier (23) and two threshold switches (24, 26), that the output of the second threshold switch (26) which is associated with a higher modulation percentage is connected to the second input of an AND circuit (29) the first input of which is directly connected to the output of a first threshold switch (24) which is associated with a lower modulation percentage and that the output signal of the AND circuit (29) controls the switch-over device (4).
5. A VHF receiver according to Claim 4, characterised in that between the output of the rectifier (23) and the input of the second threshold switch (26) a voltage divider (25) is connected, the dividing resistances of which have a ratio of 1:2 and that the two threshold switches (24, 26) are set to the same threshold value which corresponds to a modulation percentage of 60%.
6. A VH F receiver according to one of Claims 1 to 5, provided with an announcement identification decoder, characterised in that the output of the second measuring device (20) is connected to the first input of a coincidence stage (18) the second input of which is connected to the output of the announcement identification decoder (19) and that the output signal of the coincidence stage (18) controls the switch-over device (4).
EP82100826A 1981-05-27 1982-02-05 Uhf receiver for a traffic information radio broadcasting system Expired EP0065615B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82100826T ATE9413T1 (en) 1981-05-27 1982-02-05 VHF RECEIVER FOR A TRAFFIC BROADCASTING SYSTEM.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3121088A DE3121088C2 (en) 1981-05-27 1981-05-27 FM receiver
DE3121088 1981-05-27

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EP0065615A1 EP0065615A1 (en) 1982-12-01
EP0065615B1 true EP0065615B1 (en) 1984-09-12

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US (1) US4435843A (en)
EP (1) EP0065615B1 (en)
JP (1) JPS57199349A (en)
AT (1) ATE9413T1 (en)
BR (1) BR8202128A (en)
CA (1) CA1173508A (en)
DE (1) DE3121088C2 (en)
ES (1) ES8304389A1 (en)
MX (1) MX150248A (en)
ZA (1) ZA822252B (en)

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Also Published As

Publication number Publication date
ES512551A0 (en) 1983-02-16
JPH0311587B2 (en) 1991-02-18
JPS57199349A (en) 1982-12-07
ZA822252B (en) 1983-02-23
US4435843A (en) 1984-03-06
CA1173508A (en) 1984-08-28
ATE9413T1 (en) 1984-09-15
ES8304389A1 (en) 1983-02-16
MX150248A (en) 1984-04-04
BR8202128A (en) 1983-03-22
DE3121088A1 (en) 1982-12-30
EP0065615A1 (en) 1982-12-01
DE3121088C2 (en) 1986-12-04

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