EP0793361B1 - Circuit for decoding auxiliary data in a broadcast signal - Google Patents

Circuit for decoding auxiliary data in a broadcast signal Download PDF

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Publication number
EP0793361B1
EP0793361B1 EP96102902A EP96102902A EP0793361B1 EP 0793361 B1 EP0793361 B1 EP 0793361B1 EP 96102902 A EP96102902 A EP 96102902A EP 96102902 A EP96102902 A EP 96102902A EP 0793361 B1 EP0793361 B1 EP 0793361B1
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EP
European Patent Office
Prior art keywords
signal
filter
characteristic
auxiliary data
quality characteristic
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Expired - Lifetime
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EP96102902A
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German (de)
French (fr)
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EP0793361A1 (en
Inventor
Thomas Dipl.-Ing. Hilpert
Stefan Dipl.-Ing. Müller
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TDK Micronas GmbH
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TDK Micronas GmbH
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Priority to EP96102902A priority Critical patent/EP0793361B1/en
Priority to DE59611437T priority patent/DE59611437D1/en
Priority to US08/805,767 priority patent/US5978037A/en
Publication of EP0793361A1 publication Critical patent/EP0793361A1/en
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Publication of EP0793361B1 publication Critical patent/EP0793361B1/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H40/00—Arrangements specially adapted for receiving broadcast information
    • H04H40/18—Arrangements characterised by circuits or components specially adapted for receiving
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/28—Arrangements for simultaneous broadcast of plural pieces of information
    • H04H20/33—Arrangements for simultaneous broadcast of plural pieces of information by plural channels
    • H04H20/34—Arrangements for simultaneous broadcast of plural pieces of information by plural channels using an out-of-band subcarrier signal

Definitions

  • the invention relates to a circuit for decoding additional information in a signal mixture.
  • Such circuits serve to obtain additional information from the received signals of the audio or video consumption area. These are usually auxiliary information that allows the user to facilitate the operation of the respective receiving device. For example, for the motorist, the identifier of a received station as an auto information station is an important indicator. Similar additional information is also available for television signals which transmit a digital identifier for audio playback, whether the respective audio channel is a mono, stereo or multi-tone signal is.
  • this information is additionally inserted as AM or FM signal into the existing signal mixture.
  • the decoding of this additional information is usually easy to implement with known analog or after an analog / digital conversion with digital circuits.
  • the rapid change and the constant re-introduction of such additional information there are also difficulties, because under certain circumstances, the controlled by the additional information switching by adjacent channels and poor reception conditions are very disturbed and lead to false evaluations of additional information.
  • a signal quality characteristic value is formed from the received signal, which intervenes in the detection device of the respective reproduction mode controlled by an identification signal and thus forms an adaptive decoding device for the identification signal.
  • the signal quality characteristic is derived predominantly from the received field strength, but also from the broadband noise content of the received signal, which is detected by means of an FM detector or by means of an existing anyway noise reduction circuit.
  • time constants for the reproduction switching are influenced in such a way that erroneous switching over due to generally poor signal conditions or short-term disturbances is largely ruled out.
  • a simple influencing of thresholds and hystereses in the identification signal recognition device is also indicated, as a result of which the faulty switching over in the event of disturbed reception conditions is likewise reduced.
  • US 4,737,993 also describes an adaptive decoder for the respective playback mode, which is also adapted via a signal quality characteristic to the respective reception conditions, but the signal quality characteristic is determined only as a function of the reception field strength at the antenna input.
  • the sub-signal is attenuated differently depending on the signal quality characteristic before further processing in the matrix.
  • a further development consists in influencing the possibly also attenuated sub-signal before further processing in the matrix by means of a voltage-controlled filter in the frequency characteristic.
  • the upper frequency components of the sub signal are attenuated differently.
  • the solution of the problem has the advantage that existing circuit concepts can basically be used further and the improvements can be achieved via simple additional circuits. Since the signal processing is generally purely digital, it is unimportant for the processing whether additional circuits are used for the additional functions or whether the additional functions are realized via additional program steps by means of already existing processors. Here, the effort is only in a modified program.
  • the signal quality characteristic which is a measure of the quality of the received signal, can be determined at different points in the signal mixture. Of course, this depends on the type of signal mix.
  • the advantage of digital processing is that the signals are generally available as normalized signals whose value range lies within the numerical values -1 and +1. About the defined level of the carrier and its noise-induced amplitude fluctuations can then easily be determined such a quality value.
  • the general noise can be advantageously determined or a disturbing external signal.
  • Such signal ranges can be found in particular in the specified signal mixtures of the consumption range, because for compatibility reasons, the individual signal ranges usually do not overlap.
  • the additional information is coupled with different carriers, which in the frequency spectrum so are arranged so that their modulation ranges do not overlap. There should be no signal in the intermediate areas if the signal is good or the reception conditions are good.
  • About the determination of the respective noise value in these areas can, for. B. by a complementation or quotient a signal quality characteristic can be determined.
  • the improved with the Signalgütekennwert evaluation of additional information has the advantage that the filter cost can remain relatively low.
  • the increased safety in the evaluation of the disturbed additional information does not result from a higher quality of the filter. This is possible because, as it were, the interference component and not the useful signal component is detected and evaluated.
  • the determination of a relatively high noise component - a low interference component is of no interest because it does not cause false decoding - generally does not require narrow-band filters for the present signals. For blanking the useful signal range, therefore, simple notch filters or band-pass filters whose blocking range is set so that the respective useful or additional signal is largely suppressed.
  • the block diagram of Fig. 1 shows a receiving means 10 for a composite signal sf ', which is a stereo multiplex signal for the embodiment.
  • the conversion of the high-frequency transmitted signal mixture takes place in the baseband, which is shown schematically for the example given in FIG.
  • the baseband signal mixture sf is digitized and is supplied to a signal processing device 20 for audio signals, which generates the desired output signals R, L via further mixers 22 and sound processing stages 24.
  • the signals sf are further supplied to a mixer device 32, with which the additional information fz in the signal mixture sf is converted into a lower frequency position, in particular into a baseband position.
  • the individual components ki can be separated from one another by means of simple filter devices 35, 36, 37.
  • the separated components ki are then supplied to a decoder 40 to form the individual identification signals kz, for example, a mono / stereo switching signal u or an auto-radio information (ARI) signal supplied to the sound processing stage 24 and the receiving means 10, respectively.
  • a decoder 40 to form the individual identification signals kz, for example, a mono / stereo switching signal u or an auto-radio information (ARI) signal supplied to the sound processing stage 24 and the receiving means 10, respectively.
  • the processing frequencies are previously reduced by means of decimation devices in order to reduce the circuit complexity for the filters.
  • a signal-free frequency section is further detected by means of a bandpass filter 38, a signal-free frequency section to determine therefrom by means of a device 50 a signal quality characteristic kg.
  • This signal quality characteristic kg is fed to the decoder 40, which can thereby adapitively adapt to the respective reception conditions.
  • FIG. 2 shows the frequency scheme of a stereo multiplex signal sf which contains a subcarrier at 57 kHz which is modulated with additional information fz, for example an ARI identification signal.
  • the invention can also increase the reliability of the pilot signal recognition at 19 kHz. whereby the automatic stereo switching is less disturbed.
  • the signal mixture sf refers to a standardized television signal with a first and second sound carrier FM1, FM2, wherein the sound carrier FM2 contains additional information fz 'via an AM modulation. Since the additional information fz 'is in the range of the carrier FM2, the preceding processing steps for prefiltering and frequency conversion are not shown in FIG. 3 for the sake of clarity, but instead a source 310 for this preprocessed signal fz' is indicated in the preprocessing device 300.
  • the carrier FM2 is therefore no longer at the frequency 54 kHz, but at a lower frequency, for example between 8 kHz and 10 kHz.
  • the video signal, the R + L signal at the carrier FM1 and the R signal at the carrier FM2 are no longer or only as residues.
  • the output signal fz 'of the source 310 thus contains only the carrier FM2 and optionally a frequency line k1 at 171.5 Hz or a frequency line k2 at a distance of 274.1 Hz as the upper and lower sideband Frequency lines are encoded as to whether the respective audio channel contains a stereo or bilingual signal.
  • the source 310 is followed by a preprocessing device 320 for the additional information area fb (see Fig. 4), which essentially contains a decimation device with a decimation filter. Possible DC components are suppressed by a DC voltage suppression circuit 330.
  • the filtered additional signal fz is supplied to an adaptive decoding device 400 whose output supplies the desired identification signals M, S, B for monaural, stereo or double-voice operation.
  • the adaptive decoder 400 contains in the input an absolute value generator 405 serving as a signal rectifier for demodulating the AM-modulated signal fz, followed by a decimation stage 410, with which the clock frequency is reduced from 32 kHz to 2 kHz.
  • an absolute value generator 405 serving as a signal rectifier for demodulating the AM-modulated signal fz, followed by a decimation stage 410, with which the clock frequency is reduced from 32 kHz to 2 kHz.
  • a bandpass 415 and an absolute value generator 420 the amplitude of the signal k1 is determined at 171 Hz and fed to the minuend input of a subtracter 425.
  • a bandpass 430 and an absolute value generator 435 the amplitude of the signal k2 is determined at 274 Hz and fed to the subtrahend input of the subtractor 425. From the difference, a resultant characteristic value ka is formed by means of a low-pass filter 440.
  • the wanted identification signals kz or M, S, B could be determined from this characteristic value ka as in a non-adaptive decoding device.
  • a range of values from +0.2 to +1 would correspond to the stereo identification signal S
  • a range from -0.2 to +0.2 would correspond to the mono identification signal M
  • a range from -1 to -0.2 would correspond to the dual-language identity signal B.
  • the resulting characteristic ka is modified by means of the signal quality characteristic kg.
  • the switching thresholds for the modified characteristic value km are predetermined by a threshold value recognition circuit 445, wherein the threshold value position can be identical to the non-adaptive circuit.
  • the additional circuit 500 contains in its input a bandpass filter 550 which is fed with the filtered additional signal fz.
  • the middle position of this filter is expediently chosen so that the lower selection edge does not or only slightly detects the carrier FM2 with the first or second identification signal k1, k2, cf. Fig. 5.
  • the overlying frequency components should be transmitted as possible without attenuation.
  • the preceding filter 320 must therefore not come too close to the carrier FM2 with its upper selection edge, because otherwise the filter 320 already suppresses these frequencies and the bandpass filter 550 no longer finds a frequency range to be evaluated.
  • the noise or noise components at the output of the bandpass 550 are rectified by means of a squarer 555.
  • the squaring effect at the same time Weighting of the measured signal values.
  • a low-pass filter 560 smoothes the signal curve and by means of a decimator 565 the clock frequency is reduced from 32 kHz to 2 kHz.
  • the output signal of the decimator 565 corresponds to an interference characteristic value ks which lies between the values 0 and +1 and increases or decreases in parallel with the measured interference content.
  • the signal quality parameter kg is formed from this value ks by subtracting the interference parameter ks from the numerical value +1.
  • the adaptive action of the signal quality parameter kg on the original characteristic value ka is effected by means of a multiplier 575 whose output signal is a modified or adaptive characteristic value km, which supplies the desired identification signals kz or M, S, B by means of the threshold value recognition device 445.
  • the signal quality parameter kg assumes the value +1, whereby the original characteristic value ka is not changed. However, if the noise component in the filtered additional signal fz increases, then the signal quality parameter kg becomes smaller and drops, for example, to the value 0.5. The value of the original characteristics ka is thereby halved, whereby the tendency for the mono-identification signal M is increased. Individual signal outliers, which are caused by noise or foreign signals are thus prevented - for example, in mono mode or when receiving a signal without the carrier FM2 - wrong to switch the receiver. This is especially important for safe mono operation when the received signal contains neither a stereo nor a bilingual signal. As a result of the invention, however, an unsafe reception is possible only with unique identification signals k1, k2 or ka in unsecure reception conditions.
  • the digital low-pass filter 560 may also include non-linear stages or counters that are differently charged or discharged to further enhance noise suppression. It should be noted that the embodiment of Fig. 3 represents only an advantageous embodiment of the invention. Advantageous developments of individual functional units or entire functional groups are set at the discretion of the person skilled in the art.
  • FIG. 4 schematically shows the frequency scheme of a standardized television signal mix sf.
  • the frequency-modulated audio signal range with the first carrier FM1 at 5.5 MHz follows the video signal range from 0 Hz to about 5 MHz.
  • the R + L signal is transmitted in a stereo signal, which also represents the mono signal. In a multi-tone transmission, this area contains the first sound signal.
  • the second carrier FM2 which contains in frequency modulation the 2R signal or the second audio signal. From the R + L signal and the 2R signal, the R and L signals are known to be formed by means of a stereo matrix. However, there are many TV channels that do not yet broadcast this second carrier FM2.
  • the additional identifier with respect to the mono, stereo or multi-tone operation is superimposed on the carrier FM2 by means of the multiply described, very low-frequency and thus inaudible amplitude modulation.
  • FIG. 5 schematically shows the frequency scheme of the signal fz after the preprocessing device 300. So that a digital signal processing can be done at 32 kHz, the carrier FM2 has been implemented in the stage 300 from 54 kHz to 9 kHz. The signal fz no longer contains any audio information, but solely the possibly amplitude-modulated carrier FM2. The upper and lower sidebands contain either the frequency line k1 or the frequency line k2. Both are as indicated close to the carrier FM2.
  • the signal region fb separated in the preprocessing device 300 which is to contain the additional information fz and a signal-free region of the signal mixture sf, is shown schematically.
  • the associated passband of the bandpass filter 550 schematically shows the dashed line 550, which essentially detects the signal-free region in the separated signal range fb. It is irrelevant if a small proportion of the carrier FM2 is still included. Furthermore, it is irrelevant how far the passband exceeds the separated signal range fb, if it is ensured that there are no more signal components. As a result, the requirements for the filter 550 are very low and it is easy to implement with digital means.

Description

Die Erfindung betrifft eine Schaltung zur Dekodierung einer Zusatzinformation in einem Signalgemisch. Derartige Schaltungen dienen dazu, zusätzliche Infomationen aus den empfangenen Signalen des Audio- oder Videokonsumbereiches zu gewinnen. Es handelt sich dabei in der Regel um Hilfsinformationen, die dem Anwender eine erleichterte Bedienung des jeweiligen Empfangsgerätes erlauben. Beispielsweise stellt für den Autofahrer die Kennung eines empfangenen Senders als Autoinformationssender einen wichtigen Hinweis dar. Ähnliche Zusatzinformationen gibt es auch bei Fernsehsignalen, die für die Audiowiedergabe eine digitale Kennung mitübertragen, ob es sich bei dem jeweiligen Tonkanal um ein Mono-, Stereo- oder Mehrtonsignal handelt.The invention relates to a circuit for decoding additional information in a signal mixture. Such circuits serve to obtain additional information from the received signals of the audio or video consumption area. These are usually auxiliary information that allows the user to facilitate the operation of the respective receiving device. For example, for the motorist, the identifier of a received station as an auto information station is an important indicator. Similar additional information is also available for television signals which transmit a digital identifier for audio playback, whether the respective audio channel is a mono, stereo or multi-tone signal is.

Über zusätzliche Träger oder eine Mehrfachnutzung bereits vorhandener Träger werden diese Informationen als AM- oder FM-Signal zusätzlich in das vorhandene Signalgemisch eingefügt. Die Dekodierung dieser Zusatzinformation ist in der Regel einfach und mit bekannten analogen oder nach einer Analog/Digitalumsetzung mit digitalen Schaltungen leicht zu realisieren. Bei dem raschen Wechsel und der ständigen Neueinführung derartiger Zusatzinformationen gibt es jedoch auch Schwierigkeiten, weil unter Umständen die von den Zusatzinformationen gesteuerten Umschaltungen durch Nachbarkanäle und schlechte Empfangsbedingungen sehr gestört sind und zu Fehlauswertungen der Zusatzinformation führen.Via additional carriers or a multiple use of already existing carriers, this information is additionally inserted as AM or FM signal into the existing signal mixture. The decoding of this additional information is usually easy to implement with known analog or after an analog / digital conversion with digital circuits. In the rapid change and the constant re-introduction of such additional information, however, there are also difficulties, because under certain circumstances, the controlled by the additional information switching by adjacent channels and poor reception conditions are very disturbed and lead to false evaluations of additional information.

Der nächstliegende Stand der Technik ist in US 4,703,501 beschrieben. Hier wird die gewünschte Verbesserung der Empfangssituation dadurch erreicht, dass aus dem Empfangssignal ein Signalgütekennwert gebildet wird, der in die von einem Kennsignal gesteuerte Erkennungseinrichtung des jeweiligen Wiedergabemodus eingreift und so eine adaptive Dekodiereinrichtung für das Kennsignal bildet. Der Signalgütekennwert wird dabei vorwiegend aus der Empfangsfeldstärke abgeleitet, aber auch aus dem breitbandigen Rauschinhalt des Empfangssignals, das mittels eines FM-Detektors oder mittels einer sowieso vorhandenen Rauschunterdrückungsschaltung erfasst wird. Mittels des Signalgütekennwerts werden insbesondere Zeitkonstanten für die Wiedergabeumschaltungen so beeinflusst, dass fehlerhafte Umschaltungen bei insgesamt schlechten Signalbedingungen oder kurzzeitigen Störungen weitgehend ausgeschlossen werden. Angedeutet wird aber auch eine einfache Beeinflussung von Schwellen und Hysteresen in der Kennsignalerkennungseinrichtung, wodurch die fehlerhafte Umschaltungen bei gestörten Empfangsbedingungen ebenfalls reduziert werden.The closest prior art is in US 4,703,501 described. Here, the desired improvement of the reception situation is achieved in that a signal quality characteristic value is formed from the received signal, which intervenes in the detection device of the respective reproduction mode controlled by an identification signal and thus forms an adaptive decoding device for the identification signal. The signal quality characteristic is derived predominantly from the received field strength, but also from the broadband noise content of the received signal, which is detected by means of an FM detector or by means of an existing anyway noise reduction circuit. By means of the signal quality characteristic value, in particular time constants for the reproduction switching are influenced in such a way that erroneous switching over due to generally poor signal conditions or short-term disturbances is largely ruled out. However, a simple influencing of thresholds and hystereses in the identification signal recognition device is also indicated, as a result of which the faulty switching over in the event of disturbed reception conditions is likewise reduced.

US 4,737,993 beschreibt ebenfalls eine adaptive Dekodiereinrichtung für den jeweiligen Wiedergabemodus, die ebenfalls über einen Signalgütekennwert an die jeweiligen Empfangsbedingungen angepasst wird, wobei aber der Signalgütekennwert lediglich in Abhängigkeit von der Empfangsfeldstärke am Antenneneingang bestimmt wird. Zur Verbesserung der Umschaltbedingungen bei gestörten Signalen wird das Subsignal in Abhängigkeit vom Signalgütekennwert vor der weiteren Verarbeitung in der Matrix unterschiedlich gedämpft. Eine Weiterbildung besteht darin, das gegebenenfalls auch abgeschwächte Subsignal vor der Weiterverarbeitung in der Matrix mittels eines spannungsgesteuerten Filters in der Frequenzcharakteristik zu beeinflussen. Hierbei werden die oberen Frequenzanteile des Subsignals unterschiedlich gedämpft. US 4,737,993 also describes an adaptive decoder for the respective playback mode, which is also adapted via a signal quality characteristic to the respective reception conditions, but the signal quality characteristic is determined only as a function of the reception field strength at the antenna input. To improve the switching conditions for disturbed signals, the sub-signal is attenuated differently depending on the signal quality characteristic before further processing in the matrix. A further development consists in influencing the possibly also attenuated sub-signal before further processing in the matrix by means of a voltage-controlled filter in the frequency characteristic. Here, the upper frequency components of the sub signal are attenuated differently.

Es ist daher Aufgabe der Erfindung, eine gegenüber Rausch- und Störeinflüssen unempfindlichere Schaltung zur Dekodierung derartiger, in einem Signalgemisch enthaltener Zusatzinformationen anzugeben.It is therefore an object of the invention to provide a less sensitive to noise and interference influences circuit for decoding such, contained in a signal mixture additional information.

Die Aufgabe wird entsprechend den Merkmalen des Anspruchs 1 wie folgt gelöst:

  • Schaltung zur Dekodierung einer Zusatzinformation in einem Signalgemisch mit
  • einer Filtereinrichtung zur Separation eines Signalbereiches im Signalgemisch, das in kodierter Form die Zusatzinformation enthält,
  • einer adaptiven Dekodiereinrichtung, die aus dem separierten Signalbereich die Zusatzinformation unter Berücksichtigung eines Signalgütekennwertes dekodiert, und
  • einer Einrichtung zur Bestimmung des Signalgütekennwertes aus dem jeweiligen Empfangszustand des Signalgemisches oder des separierten Signalbereiches.
The object is achieved according to the features of claim 1 as follows:
  • Circuit for decoding additional information in a composite signal with
  • a filter device for separating a signal region in the signal mixture, which contains the additional information in coded form,
  • an adaptive decoding device which decodes the additional information taking into account a signal quality characteristic from the separated signal region, and
  • a device for determining the signal quality characteristic from the respective reception state of the signal mixture or the separated signal region.

Die Lösung der Aufgabe hat den Vorteil, daß vorhandene Schaltungskonzepte grundsätzlich weiter verwendet werden können und die Verbesserungen über einfache Zusatzschaltungen erreicht werden. Da die Signalverarbeitung in der Regel rein digital ist, ist es für die Verarbeitung unwesentlich, ob für die zusätzlichen Funktionen Zusatzschaltungen verwendet werden oder ob die zusätzliche Funktionen über zusätzliche Programmschritte mittels bereits vorhandenen Prozessoren realisiert werden. Hierbei besteht der Aufwand nur in einem geänderten Programm.The solution of the problem has the advantage that existing circuit concepts can basically be used further and the improvements can be achieved via simple additional circuits. Since the signal processing is generally purely digital, it is unimportant for the processing whether additional circuits are used for the additional functions or whether the additional functions are realized via additional program steps by means of already existing processors. Here, the effort is only in a modified program.

Der Signalgütekennwert, der ein Maß für die Qualität des empfangenen Signals ist, läßt sich an verschiedenen Stellen des Signalgemisches bestimmen. Das hängt selbstverständlich von der Art des jeweiligen Signalgemisches ab. Die digitale Verarbeitung hat hierbei den Vorteil, daß die Signale in der Regel als normierte Signale vorliegen, deren Wertebereich innerhalb der Zahlenwerte -1 und +1 liegt. Über die definierten Pegel der Träger und ihre rauschbedingten Amplitudenschwankungen kann dann leicht ein derartiger Gütewert bestimmt werden.The signal quality characteristic, which is a measure of the quality of the received signal, can be determined at different points in the signal mixture. Of course, this depends on the type of signal mix. The advantage of digital processing is that the signals are generally available as normalized signals whose value range lies within the numerical values -1 and +1. About the defined level of the carrier and its noise-induced amplitude fluctuations can then easily be determined such a quality value.

Wenn sich im Signalspektrum Bereiche finden, in denen kein Signal vorhanden sein sollte, dann kann mit einer Pegelmessung in diesem Bereich auf vorteilhafte Weise das allgemeine Rauschen bestimmt werden oder ein störendes Fremdsignal. Derartige Signalbereiche finden sich insbesondere bei den angegebenen Signalgemischen des Konsumbereiches, weil sich bei diesen aus Kompatibilitätsgründen die einzelnen Signalbereiche meist nicht überlappen. In der Regel sind die zusätzlichen Informationen mit verschiedenen Trägern verkoppelt, die im Frequenzspektrum so angeordnet sind, daß sich deren Modulationsbereiche nicht überlappen. In den Zwischenbereichen sollte bei einem ordnungsgemäßen Signal oder bei guten Empfangsverhältnissen kein Signal vorhanden sein. Über die Bestimmung des jeweiligen Rauschwertes in diesen Bereichen kann z. B. durch eine Komplementbildung oder Quotientenbildung ein Signalgütekennwert bestimmt werden.If there are areas in the signal spectrum in which no signal should be present, then with a level measurement in this area the general noise can be advantageously determined or a disturbing external signal. Such signal ranges can be found in particular in the specified signal mixtures of the consumption range, because for compatibility reasons, the individual signal ranges usually do not overlap. In general, the additional information is coupled with different carriers, which in the frequency spectrum so are arranged so that their modulation ranges do not overlap. There should be no signal in the intermediate areas if the signal is good or the reception conditions are good. About the determination of the respective noise value in these areas can, for. B. by a complementation or quotient a signal quality characteristic can be determined.

Mit dem Signalgütekennwert lassen sich in der Dekodiereinrichtung einzelne oder alle Kennwerte gewichten und/oder zugehörige Bewertungsschwellen verändern. Dadurch wird eine zuvor starre Dekodiereinrichtung an die Empfangsbedingungen angepaßt.With the signal quality characteristic, individual or all characteristic values can be weighted in the decoding device and / or associated evaluation thresholds can be changed. As a result, a previously rigid decoding device is adapted to the reception conditions.

Die mit dem Signalgütekennwert verbesserte Auswertung der Zusatzinformation hat den Vorteil, daß der Filteraufwand relativ gering bleiben kann. Die erhöhte Sicherheit bei der Auswertung der gestörten Zusatzinformation ergibt sich nämlich nicht aus einer höheren Güte der Filter. Dies ist möglich, weil gleichsam der Störanteil und nicht der Nutzsignalanteil erfaßt und bewertet wird. Die Bestimmung eines relativ hohen Störanteils - ein niedriger Störanteil ist uninteressant, weil er keine Falschdekodierung verusacht - erfordert bei den vorliegenden Signalen in der Regel keine schmalbandigen Filter. Zur Ausblendung des Nutzsignalbereiches eignen sich daher einfache Kerbfilter oder Bandpässe, deren Sperrbereich so gelegt wird, daß das jeweilige Nutz- oder Zusatzsignal weitgehend unterdrückt wird.The improved with the Signalgütekennwert evaluation of additional information has the advantage that the filter cost can remain relatively low. The increased safety in the evaluation of the disturbed additional information does not result from a higher quality of the filter. This is possible because, as it were, the interference component and not the useful signal component is detected and evaluated. The determination of a relatively high noise component - a low interference component is of no interest because it does not cause false decoding - generally does not require narrow-band filters for the present signals. For blanking the useful signal range, therefore, simple notch filters or band-pass filters whose blocking range is set so that the respective useful or additional signal is largely suppressed.

Die Erfindung und weitere vorteilhafte Ausgestaltungen werden nun anhand der Figuren der Zeichnung näher erläutert:

  • Fig. 1 zeigt schematisch als Blockschaltbild ein Ausführungsbeispiel der Erfindung zur Dekodierung einer Zusatzfunktion in einem Stereo-Multiplexsignal,
  • Fig. 2 zeigt das zugehörige Frequenzschema,
  • Fig 3 zeigt als Blockschaltbild ein weiteres Ausführungsbeispiel der Erfindung und
  • Fig. 4 und Fig. 5 stellen jeweils ein zugehöriges Frequenzschema dar.
The invention and further advantageous embodiments will now be described with reference to the figures of the drawing:
  • 1 shows schematically as a block diagram an embodiment of the invention for decoding an additional function in a stereo multiplex signal,
  • 2 shows the associated frequency scheme,
  • 3 shows a block diagram of a further embodiment of the invention and
  • FIGS. 4 and 5 each illustrate an associated frequency scheme.

Das Blockschaltbild von Fig. 1 zeigt eine Empfangseinrichtung 10 für ein Signalgemisch sf', das für das Ausführungsbeispiel ein Stereo-Multiplexsignal ist. In der Empfangseinrichtung 10 findet die Umsetzung des hochfrequent übertragenen Signalgemisches in das Basisband statt, das für das angegebene Beispiel in Fig. 2 schematisch dargestellt ist. Das im Basisband befindliche Signalgemisch sf ist digitalisiert und wird einer Signalverarbeitungseinrichtung 20 für Tonsignale zugeführt, die über weitere Mischer 22 und Tonverarbeitungsstufen 24 die gewünschten Ausgangssignale R, L erzeugt. Die Signale sf werden ferner einer Mischereinrichtung 32 zugeführt, mit der die Zusatzinformation fz im Signalgemisch sf in eine tiefere Frequenzlage, insbesondere in eine Basisbandlage umgesetzt wird.The block diagram of Fig. 1 shows a receiving means 10 for a composite signal sf ', which is a stereo multiplex signal for the embodiment. In the receiving device 10, the conversion of the high-frequency transmitted signal mixture takes place in the baseband, which is shown schematically for the example given in FIG. The baseband signal mixture sf is digitized and is supplied to a signal processing device 20 for audio signals, which generates the desired output signals R, L via further mixers 22 and sound processing stages 24. The signals sf are further supplied to a mixer device 32, with which the additional information fz in the signal mixture sf is converted into a lower frequency position, in particular into a baseband position.

Wird beispielsweise die bei 57 kHz liegende Zusatzinformation fz in das Basisband transformiert, dann können die einzelnen Komponenten ki mittels einfacher Filtereinrichtungen 35, 36, 37 voneinander getrennt werden. Die getrennten Komponenten ki werden danach einer Dekodiereinrichtung 40 zugeführt, um die einzelnen Kennungssignale kz zu bilden, beispielsweise ein Mono/Stereo-Umschaltsignal u oder ein ARI-Kennungssignal (Auto-Radio Information), das der Tonverarbeitungsstufe 24 bzw der Empfangseinrichtung 10 zugeführt wird.If, for example, the additional information fz lying at 57 kHz is transformed into the baseband, then the individual components ki can be separated from one another by means of simple filter devices 35, 36, 37. The separated components ki are then supplied to a decoder 40 to form the individual identification signals kz, for example, a mono / stereo switching signal u or an auto-radio information (ARI) signal supplied to the sound processing stage 24 and the receiving means 10, respectively.

Zur Trennung der einzelnen Komponenten ki in der Filtereinrichtung 34 oder in den Tief- oder Bandpässen 35, 36, 37 werden zuvor die Verarbeitungsfrequenzen mittels Dezimierungseinrichtungen heruntergesetzt, um den Schaltungsaufwand für die Filter zu verkleinern. Aus dem Signal fz wird ferner mittels eines Bandpasses 38 ein signalfreier Frequenzabschnitt erfaßt, um daraus mittels einer Einrichtung 50 einen Signalgütekennwert kg zu bestimmen. Dieser Signalgütekennwert kg wird der Dekodiereinrichtung 40 zugeführt, die sich dadurch adapitiv an die jeweiligen Empfangsbedingungen anpassen kann.In order to separate the individual components ki in the filter device 34 or in the low-pass or band-pass filters 35, 36, 37, the processing frequencies are previously reduced by means of decimation devices in order to reduce the circuit complexity for the filters. From the signal fz is further detected by means of a bandpass filter 38, a signal-free frequency section to determine therefrom by means of a device 50 a signal quality characteristic kg. This signal quality characteristic kg is fed to the decoder 40, which can thereby adapitively adapt to the respective reception conditions.

In Fig. 2 wird das Frequenzschema eines Stereo- Multiplexsignals sf dargestellt, das bei 57 kHz einen Hilfsträger enthält, der mit einer Zusatzinformation fz, beispielsweise einem ARI-Kennungssignal moduliert ist Ebenso kann durch die Erfindung die Sicherherheit der Pilotsignalerkennung bei 19 kHz erhöht werden, wodurch die automatische Stereoumschaltung weniger gestört wird.FIG. 2 shows the frequency scheme of a stereo multiplex signal sf which contains a subcarrier at 57 kHz which is modulated with additional information fz, for example an ARI identification signal. The invention can also increase the reliability of the pilot signal recognition at 19 kHz. whereby the automatic stereo switching is less disturbed.

In Fig. 3 sind die wesentlichen Funktionseinheiten der Erfindung anhand eines weiteren Ausführungsbeispiels dargestellt. Dabei bezieht sich das Signalgemisch sf (vgl. Fig. 4) auf ein standardisiertes Fernsehsignal mit einem ersten und zweiten Tonträger FM1, FM2, wobei der Tonträger FM2 eine zusätzliche Information fz' über eine AM-Modulation enthält. Da die Zusatzinformation fz' im Bereich des Trägers FM2 liegt, sind der besseren Übersicht wegen die vorausgehenden Verarbeitungsstufen zur Vorfilterung und Frequenzumsetzung in Fig. 3 nicht dargestellt, sondern statt dessen wird in der Vorverarbeitungseinrichtung 300 eine Quelle 310 für dieses vorverarbeitete Signal fz' angegeben. Beim Ausgangssignal fz' liegt der Träger FM2 somit nicht mehr bei der Frequenz 54 kHz, sondern bei einer tieferen Frequenz, beispielsweise zwischen 8 kHz und 10 kHz. Das Videosignal, das R+L-Signal beim Träger FM1 und das R-Signal beim Träger FM2 sind nicht mehr oder nur als Reste vorhanden. Das Ausgangssignal fz' der Quelle 310 enthält somit je nach der mittels AM übertragenen Zusatzinformation nur noch den Träger FM2 und gegebenenfalls als oberes und unteres Seitenband eine Frequenzlinie k1 jeweils im Abstand von 171.5 Hz oder eine Frequenzlinie k2 im Abstand von 274.1 Hz. Mit diesen beiden Frequenzlinien wird kodiert, ob der jeweilige Audiokanal ein Stereo- oder Zweisprachensignal enthält. Wenn keine der Frequenzlinien k1, k2 vorhanden ist - also der Träger FM2 nicht amplitudenmoduliert ist - dient diese Information als Kennung, daß der jeweilige Audiokanal nur ein Monosignal enthält. Die Schwierigkeiten bei der Dekodierung ergeben sich, wenn durch Empfangsstörungen oder Fremdsignale die Trennung erschwert wird. Eine gewisse Abhilfe schaffen schmalbandige Filter für die Kennungssignale k1, k2, das Ergebnis bleibt jedoch trotz des erhöhten Aufwandes unbefriedigend.In Fig. 3, the essential functional units of the invention are illustrated by a further embodiment. In this case, the signal mixture sf (see Fig. 4) refers to a standardized television signal with a first and second sound carrier FM1, FM2, wherein the sound carrier FM2 contains additional information fz 'via an AM modulation. Since the additional information fz 'is in the range of the carrier FM2, the preceding processing steps for prefiltering and frequency conversion are not shown in FIG. 3 for the sake of clarity, but instead a source 310 for this preprocessed signal fz' is indicated in the preprocessing device 300. With the output signal fz ', the carrier FM2 is therefore no longer at the frequency 54 kHz, but at a lower frequency, for example between 8 kHz and 10 kHz. The video signal, the R + L signal at the carrier FM1 and the R signal at the carrier FM2 are no longer or only as residues. Depending on the additional information transmitted by means of AM, the output signal fz 'of the source 310 thus contains only the carrier FM2 and optionally a frequency line k1 at 171.5 Hz or a frequency line k2 at a distance of 274.1 Hz as the upper and lower sideband Frequency lines are encoded as to whether the respective audio channel contains a stereo or bilingual signal. If none of the frequency lines k1, k2 is present - ie the carrier FM2 is not amplitude modulated - this information serves as an identifier that the respective audio channel contains only one mono signal. The difficulties in decoding arise when the separation is hampered by interference or foreign signals. Narrow-band filters for the identification signals k1, k2 provide a certain remedy, but the result remains unsatisfactory despite the increased complexity.

An die Quelle 310 schließt sich eine Vorverarbeitungseinrichtung 320 für den Zusatzinformationsbereich fb (vgl. Fig. 4) an, die im wesentlichen eine Dezimierungseinrichtung mit einem Dezimierungsfilter enthält. Mögliche Gleichspannungsanteile werden durch eine Gleichspannungs-Unterdrückungsschaltung 330 unterdrückt. Das gefilterte Zusatzsignal fz ist einer adaptiven Dekodiereinrichtung 400 zugeführt, deren Ausgang die gewünschte Kennungssignale M, S, B für den Mono-, Stereo- oder Zweisprachenbetrieb liefert.The source 310 is followed by a preprocessing device 320 for the additional information area fb (see Fig. 4), which essentially contains a decimation device with a decimation filter. Possible DC components are suppressed by a DC voltage suppression circuit 330. The filtered additional signal fz is supplied to an adaptive decoding device 400 whose output supplies the desired identification signals M, S, B for monaural, stereo or double-voice operation.

Die adaptive Dekodiereinrichtung 400 enthält im Eingang einen als Signalgleichrichter dienenden Absolutwertbildner 405 zur Demodulation des AM-modulierten Signals fz, daran schließt sich eine Dezimationsstufe 410 an, mit der die Taktfrequenz von 32 kHz auf 2 kHz herabgesetzt wird. Mittels eines Bandpasses 415 und eines Absolutwertbildners 420 wird die Amplitude des Signals k1 bei 171 Hz bestimmt und dem Minuendeingang eines Subtrahierers 425 zugeführt. Mittels eines Bandpasses 430 und eines Absolutwertbildners 435 wird die Amplitude des Signals k2 bei 274 Hz bestimmt und dem Subtrahendeingang des Subtrahierers 425 zugeführt. Aus der Differenz wird mittels eines Tiefpasses 440 ein resultierender Kennwert ka gebildet. Über entsprechende Schaltschwellen könnten wie bei einer nichtadaptiven Dekodiereinrichtung aus diesem Kennwert ka die gesuchten Kennungssignale kz bzw. M, S, B bestimmt werden. Beispielsweise entspräche ein Wertebereich von +0,2 bis +1 dem Stereo-Kennungssignal S, ein Bereich von -0,2 bis +0,2 dem Mono-Kennungssignal M und ein Bereich von -1 bis -0,2 dem Zweisprachen-Kennungssignal B. Nach der Erfindung wird der resultierende Kennwert ka jedoch mittels des Signalgütekennwertes kg modifiziert. Die Schaltschwellen für den modifizierten Kennwert km sind durch eine Schwellwert-Erkennungsschaltung 445 vorgegeben, wobei die Schwellwertlage identisch zur nichtadaptiven Schaltung sein kann.The adaptive decoder 400 contains in the input an absolute value generator 405 serving as a signal rectifier for demodulating the AM-modulated signal fz, followed by a decimation stage 410, with which the clock frequency is reduced from 32 kHz to 2 kHz. By means of a bandpass 415 and an absolute value generator 420, the amplitude of the signal k1 is determined at 171 Hz and fed to the minuend input of a subtracter 425. By means of a bandpass 430 and an absolute value generator 435, the amplitude of the signal k2 is determined at 274 Hz and fed to the subtrahend input of the subtractor 425. From the difference, a resultant characteristic value ka is formed by means of a low-pass filter 440. By means of appropriate switching thresholds, the wanted identification signals kz or M, S, B could be determined from this characteristic value ka as in a non-adaptive decoding device. For example, a range of values from +0.2 to +1 would correspond to the stereo identification signal S, a range from -0.2 to +0.2 would correspond to the mono identification signal M, and a range from -1 to -0.2 would correspond to the dual-language identity signal B. According to the invention, however, the resulting characteristic ka is modified by means of the signal quality characteristic kg. The switching thresholds for the modified characteristic value km are predetermined by a threshold value recognition circuit 445, wherein the threshold value position can be identical to the non-adaptive circuit.

Die Zusatzschaltung 500, mit der die adaptive Steuerung nach der Erfindung ermöglicht wird, enthält in ihrem Eingang ein Bandfilter 550 das mit dem gefilterten Zusatzsignal fz gespeist ist. Die Mittellage dieses Filters wird zweckmäßigerweise so gewählt, daß die untere Selektionsflanke den Träger FM2 mit dem ersten oder zweiten Kennungssignal k1, k2 nicht oder nur gering erfaßt, vgl. Fig. 5. Die darüberliegenden Frequenzanteile sollen jedoch möglichst ohne Dämpfung durchgelassen werden. Das vorausgehende Filter 320 darf daher mit seiner oberen Selektionsflanke nicht zu dicht an den Träger FM2 herankommen, weil ansonsten bereits das Filter 320 diese Frequenzen unterdrückt und der Bandpaß 550 keinen auszuwertenden Frequenzbereich mehr vorfindet.The additional circuit 500, with which the adaptive control is made possible according to the invention, contains in its input a bandpass filter 550 which is fed with the filtered additional signal fz. The middle position of this filter is expediently chosen so that the lower selection edge does not or only slightly detects the carrier FM2 with the first or second identification signal k1, k2, cf. Fig. 5. However, the overlying frequency components should be transmitted as possible without attenuation. The preceding filter 320 must therefore not come too close to the carrier FM2 with its upper selection edge, because otherwise the filter 320 already suppresses these frequencies and the bandpass filter 550 no longer finds a frequency range to be evaluated.

Die Rausch- oder Störsignalanteile am Ausgang des Bandpasses 550 werden mittels eines Quadrierers 555 gleichgerichtet. Die Quadrierung bewirkt zugleich eine Gewichtung der gemessenen Signalwerte. Ein Tiefpaß 560 glättet den Signalverlauf und mittels einer Dezimiereinrichtung 565 wird die Taktfrequenz von 32 kHz auf 2 kHz reduziert. Das Ausgangssignal der Dezimiereinrichtung 565 entspricht einem zwischen den Werten 0 und +1 liegenden Störkennwert ks, der mit dem gemessenen Störinhalt gleichlaufend zu- oder abnimmt. Mittels eines Subtrahierers 570 wird aus diesem Wert ks der Signalgütekennwert kg gebildet, indem der Störkennwert ks vom Zahlenwert +1 abgezogen wird.The noise or noise components at the output of the bandpass 550 are rectified by means of a squarer 555. The squaring effect at the same time Weighting of the measured signal values. A low-pass filter 560 smoothes the signal curve and by means of a decimator 565 the clock frequency is reduced from 32 kHz to 2 kHz. The output signal of the decimator 565 corresponds to an interference characteristic value ks which lies between the values 0 and +1 and increases or decreases in parallel with the measured interference content. By means of a subtracter 570, the signal quality parameter kg is formed from this value ks by subtracting the interference parameter ks from the numerical value +1.

Die adaptive Einwirkung des Signalgütekennwertes kg auf den ursprünglichen Kennwert ka erfolgt mittels eines Multiplizierers 575, dessen Ausgangssignal ein modifizierter oder adaptiver Kennwert km ist, der mittels der Schwellwert-Erkennungseinrichtung 445 die gewünschten Kennungssignale kz bzw. M, S, B liefert.The adaptive action of the signal quality parameter kg on the original characteristic value ka is effected by means of a multiplier 575 whose output signal is a modified or adaptive characteristic value km, which supplies the desired identification signals kz or M, S, B by means of the threshold value recognition device 445.

Liegen keine Störsignale vor, dann nimmt der Signalgütekennwert kg den Wert +1 an, wodurch der ursprüngliche Kennwert ka nicht verändert wird. Erhöht sich jedoch der Rauschanteil im gefilterten Zusatzsignal fz, dann wird der Signalgütekennwert kg kleiner und sinkt beispielsweise auf den Wert 0,5. Der Wert der ursprünglichen Kennwerte ka wird dadurch halbiert, wodurch die Tendenz für das Mono-Kennungssignal M verstärkt wird. Einzelne Signalausreißer, die durch Rausch- oder Fremdsignale bedingt sind, werden somit - beispielsweise im Monobetrieb oder beim Empfang eines Signals ohne den Träger FM2 - daran gehindert, den Empfänger fälschlicherweise umzuschalten. Das ist insbesondere für einen sicheren Monobetrieb wichtig, wenn das empfangene Signal weder ein Stereo- noch ein Zweisprachensignal enthält. Infolge der Erfindung ist bei unsicheren Empfangsbedingungen jedoch ein selbstätiges Umschalten nur bei eindeutigen Kennungssignalen k1, k2 bzw. ka möglich.If there are no interference signals, then the signal quality parameter kg assumes the value +1, whereby the original characteristic value ka is not changed. However, if the noise component in the filtered additional signal fz increases, then the signal quality parameter kg becomes smaller and drops, for example, to the value 0.5. The value of the original characteristics ka is thereby halved, whereby the tendency for the mono-identification signal M is increased. Individual signal outliers, which are caused by noise or foreign signals are thus prevented - for example, in mono mode or when receiving a signal without the carrier FM2 - wrong to switch the receiver. This is especially important for safe mono operation when the received signal contains neither a stereo nor a bilingual signal. As a result of the invention, however, an unsafe reception is possible only with unique identification signals k1, k2 or ka in unsecure reception conditions.

Der digitale Tiefpaß 560 kann auch nichtlineare Stufen oder Zähler enthalten, die unterschiedlich auf- oder entladen werden, um die Störunterdrückung weiter zu verbessern. Es wird darauf hingewiesen, daß das Ausführungsbeispiel von Fig. 3 nur ein vorteilhaftes Ausführungsbeispiel für die Erfindung darstellt. Vorteilhafte Weiterbildungen einzelner Funktionseinheiten oder ganzer Funktionsgruppen sind in das Belieben des Fachmannes gestellt.The digital low-pass filter 560 may also include non-linear stages or counters that are differently charged or discharged to further enhance noise suppression. It should be noted that the embodiment of Fig. 3 represents only an advantageous embodiment of the invention. Advantageous developments of individual functional units or entire functional groups are set at the discretion of the person skilled in the art.

In Fig 4 ist schematisch das Frequenzschema eines standardisierten Fernseh-Signalgemisches sf dargestellt. An den Videosignalbereich von 0 Hz bis ca 5 MHz schließt sich der frequenzmodulierte Tonsignalbereich mit dem ersten Träger FM1 bei 5,5 MHz an. In diesem Bereich wird bei einem Stereosignal das R+L-Signal übertragen, das auch das Monosignal darstellt. Bei einer Mehrtonübertragung enthält dieser Bereich das erste Tonsignal. Bei der Frequenz 5,74 MHz liegt der zweite Träger FM2, der in Frequenzmodulation das 2R-Signal oder das zweite Tonsignal enthält. Aus dem R+L-Signal und dem 2R-Signal wird mittels einer Stereomatrix bekanntlich das R- und das L-Signal gebildet. Es gibt jedoch viele Fernsehsender, die diesen zweiten Träger FM2 noch gar nicht aussenden. Die zusätzliche Kennung bezüglich des Mono-, Stereo- oder Mehrtonbetriebes ist dem Träger FM2 mittels der mehrfach beschriebenen, sehr niederfrequenten und damit nicht hörbaren Amplitudenmodulation überlagert.FIG. 4 schematically shows the frequency scheme of a standardized television signal mix sf. The frequency-modulated audio signal range with the first carrier FM1 at 5.5 MHz follows the video signal range from 0 Hz to about 5 MHz. In this range, the R + L signal is transmitted in a stereo signal, which also represents the mono signal. In a multi-tone transmission, this area contains the first sound signal. At the 5.74 MHz frequency is the second carrier FM2, which contains in frequency modulation the 2R signal or the second audio signal. From the R + L signal and the 2R signal, the R and L signals are known to be formed by means of a stereo matrix. However, there are many TV channels that do not yet broadcast this second carrier FM2. The additional identifier with respect to the mono, stereo or multi-tone operation is superimposed on the carrier FM2 by means of the multiply described, very low-frequency and thus inaudible amplitude modulation.

In Fig. 5 ist schließlich das Frequenzschema des Signals fz nach der Vorverarbeitungseinrichtung 300 schematisch dargestellt. Damit eine digitale Signalverarbeitung mit 32 kHz erfolgen kann, ist der Träger FM2 in der Stufe 300 von 54 kHz auf 9 kHz umgesetzt worden. Das Signal fz enthält keinerlei Toninformation mehr, sondern alleine den gegebenenfalls amplitudenmodulierten Träger FM2. Das obere und untere Seitenband enthalten entweder die Frequenzlinie k1 oder die Frequenzlinie k2. Beide liegen wie angedeutet dicht beim Träger FM2. Der in der Vorverarbeitungseinrichtung 300 separierte Signalbereich fb, der die Zusatzinformation fz und einen signalfreien Bereich des Signalgemisches sf enthalten soll, ist schematisch dargestellt. Den zugehörigen Durchlaßbereich des Bandfilters 550 zeigt schematisch die gestrichelte Linie 550, die im wesentlichen den signalfreien Bereich im separierten Signalbereich fb erfaßt. Es ist dabei unerheblich, wenn ein geringer Anteil des Trägers FM2 noch miterfaßt wird. Ferner ist es unerheblich, wie weit der Durchlaßbereich den separierten Signalbereich fb überschreitet, wenn sichergestellt ist, daß dort keine Signalanteile mehr vorhanden sind. Dadurch sind die Anforderungen an das Filter 550 sehr gering und es ist mit digitalen Mitteln einfach zu realisieren.Finally, FIG. 5 schematically shows the frequency scheme of the signal fz after the preprocessing device 300. So that a digital signal processing can be done at 32 kHz, the carrier FM2 has been implemented in the stage 300 from 54 kHz to 9 kHz. The signal fz no longer contains any audio information, but solely the possibly amplitude-modulated carrier FM2. The upper and lower sidebands contain either the frequency line k1 or the frequency line k2. Both are as indicated close to the carrier FM2. The signal region fb separated in the preprocessing device 300, which is to contain the additional information fz and a signal-free region of the signal mixture sf, is shown schematically. The associated passband of the bandpass filter 550 schematically shows the dashed line 550, which essentially detects the signal-free region in the separated signal range fb. It is irrelevant if a small proportion of the carrier FM2 is still included. Furthermore, it is irrelevant how far the passband exceeds the separated signal range fb, if it is ensured that there are no more signal components. As a result, the requirements for the filter 550 are very low and it is easy to implement with digital means.

Claims (6)

  1. Circuit for decoding auxiliary data (fz) in a composite signal (sf), with
    - a filter device (34; 300) for separating a signal range (fb) in the composite signal (sf), which contains the auxiliary data (fz) in an encoded form,
    - an adaptive decoding device (40; 400) for decoding the auxiliary data (fz) from the separated signal range (fb) while taking into consideration a signal quality characteristic (kg) and
    - a device (50; 500) for determining the signal quality characteristic (kg),
    characterised in that
    the device (50; 500) determines the signal quality characteristic (kg) of the composite signal (sf) from the noise signal contained therein by means of a filter (38; 550), wherein the frequency range of the composite signal used for the determination of the signal quality characteristic is converted into a baseband position and does not have any useful signal content in a composite signal corresponding to standards.
  2. Circuit according to claim 1, characterised in that the adaptive decoding device (40; 400) is suitable for modifying at least one characteristic (ki; ka) and/or at least one evaluation threshold.
  3. Circuit according to claim 1, characterised in that the filter (38; 550) is designed such that the pass band range substantially covers the separated signal range (fb), the auxiliary data (fz) either lying in the stop band or being suppressed by separate filter means.
  4. Circuit according to claim 3, characterised in that the filter (38; 550) contains as a filter means a notch or band filter, the notch or stop band of which suppresses the auxiliary data (fz).
  5. Circuit according to claim 3 or 4, characterised in that the output signal of the filter (38;550), squared and low-pass filtered in subsequent stages (550; 560), represents a noise characteristic (ks) subtracted from a predetermined numerical value by means of a subtracting circuit (575), the output value of the subtracting circuit (575) being the signal quality characteristic (kg).
  6. Circuit according to any of claims 1 to 5, characterised in that at least one characteristic (ka; ki) is multiplied by the signal quality characteristic (kg) in the adaptive decoding device (40; 400).
EP96102902A 1996-02-27 1996-02-27 Circuit for decoding auxiliary data in a broadcast signal Expired - Lifetime EP0793361B1 (en)

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US08/805,767 US5978037A (en) 1996-02-27 1997-02-25 Circuit for decoding additional information in a composite signal

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