EP0691049B1 - Methode pour la derivation d'un signal de qualite dependant de la qualite d'un signal multiplex de reception - Google Patents

Methode pour la derivation d'un signal de qualite dependant de la qualite d'un signal multiplex de reception Download PDF

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Publication number
EP0691049B1
EP0691049B1 EP94911061A EP94911061A EP0691049B1 EP 0691049 B1 EP0691049 B1 EP 0691049B1 EP 94911061 A EP94911061 A EP 94911061A EP 94911061 A EP94911061 A EP 94911061A EP 0691049 B1 EP0691049 B1 EP 0691049B1
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EP
European Patent Office
Prior art keywords
signal
signals
multiplied
quality
mixed signals
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP94911061A
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German (de)
English (en)
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EP0691049A1 (fr
Inventor
Djahanyar Chahabadi
Matthias Hermann
Lothar Vogt
Jürgen KÄSSER
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Blaupunkt Werke GmbH
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Blaupunkt Werke GmbH
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Priority claimed from DE4309518A external-priority patent/DE4309518A1/de
Application filed by Blaupunkt Werke GmbH filed Critical Blaupunkt Werke GmbH
Publication of EP0691049A1 publication Critical patent/EP0691049A1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/12—Arrangements for observation, testing or troubleshooting
    • 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
    • H04H40/27—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95
    • H04H40/36—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving
    • H04H40/45—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast systems receiving

Definitions

  • the invention relates to a method for deriving a quality signal dependent on the quality of a received multiplex signal in a stereo broadcast receiver, the multiplex signal being a sum signal (L + R) in baseband, a subcarrier modulated with a difference signal (LR) and a pilot signal with half Frequency of the subcarrier contains.
  • the reception quality can fluctuate greatly - for example due to drops in the received field strength, through multi-path reception or through the reception of interference signals.
  • various measures for masking these interference in the LF signal are known. In the event of poor reception, for example, it is possible to temporarily attenuate the LF signal or to reduce the stereo channel separation.
  • these known measures require that the signal quality can be determined correctly.
  • An FM car radio is known from EP 0 472 865 A2, in which a detection of interference, in particular caused by multipath reception, from the LF signal to be reproduced is provided.
  • the difference signal and the sum signal from the LF signal for the right and left channel (U LR, U L + R ) are phase-shifted with the 38 kHz subcarrier or with the 38 kHz subcarrier with respect to the suppressed 38 kHz subcarrier 38 kHz subcarrier multiplied and the product signals thus formed after low-pass filtering, rectification and another low-pass filtering fed to a quotient.
  • the output signal of the quotient generator represents a quality signal which indicates disturbances in the received LF signal and which, after evaluation by a threshold value circuit, brings about a readjustment of the receiving part of the car radio.
  • the object of the present invention is to provide a method for deriving at least one quality signal which is dependent on the quality of a received signal.
  • the method according to the invention enables the detection of audible disturbances and is based on the evaluation of the symmetry of the auxiliary carrier-frequency stereo difference signal. It is essential in this procedure that an undisturbed signal must be symmetrical to the carrier due to the two-sideband amplitude modulation. In the method according to the invention, this symmetry is in the case of an undisturbed Signals guaranteed by in-phase feeding of the sidebands to be compared. An asymmetry therefore leads to the conclusion that there is an audible disturbance in the LF signal.
  • a further development of the invention contributes to symmetry in the undisturbed case in that the signals multiplied by the phase-shifted reference pilot signals are low-pass filtered, and in that the further mixed signals thus created are squared and subtracted from one another to form the first correction signal and to form the second Correction signal with each other and multiplied by the value 2.
  • Formation of the first correction signal are squared and subtracted from one another and are multiplied with one another and with two to form the second correction signal.
  • the effect of a fluctuation in the amplitude of the pilot signal which is not relevant for the purposes of the method according to the invention can be suppressed by squaring and adding the low-pass filtered further mixed signals to form a signal representing the amplitude of the pilot signal, and by the correction signals using the amplitude of the pilot signal representing signal can be controlled in the sense of normalizing their amplitude.
  • the direction of the asymmetry of the sidebands is not important, so that an amount is provided after the low-pass filter. This is preferably done by squaring.
  • the quality signal derived with the method may well be an analog signal that can take intermediate values between two limit values.
  • a binary signal can be used for many purposes.
  • One embodiment of the invention therefore provides that the amount formed is compared with a threshold value and the comparison result is output as a quality signal.
  • circuit arrangement according to the invention is limited to implementation using individual circuits corresponding to the blocks. Rather, the circuit arrangement according to the invention can be implemented in a particularly advantageous manner with the aid of highly integrated circuits. In this case, digital signal processors can be used which, with suitable programming, carry out the processing steps shown in the block diagrams.
  • the circuit arrangement according to the invention together with further circuit arrangements within an integrated circuit, can form essential parts of a radio receiver.
  • a digital multiplex signal MPX is fed via an input 1, which contains a sum signal L + R, a subcarrier modulated with a difference signal LR and a pilot signal in a manner known per se.
  • the frequency of the auxiliary carrier is 38 kHz, while the pilot signal has a frequency of 19 kHz.
  • the angular frequency of the pilot signal is referred to below as w p .
  • multipliers 2, 3, 4, 5 and an adder 6 are provided in the stereo decoder according to FIG. 1, from whose output the demodulated difference signal LR together with the multiplex signal one of two further adders via a further multiplier 7 8, 9 existing matrix circuit is supplied.
  • the decoded digital stereo audio signals L and R reach outputs 12, 13 via two low-pass filters 10, 11.
  • the multiplex signal is first multiplied by a reference carrier, the multiplication in 3 being carried out with a reference carrier which is phase-shifted by 90 ° compared to the multiplication in 2.
  • the samples of the reference carriers are read from a table 14, the frequency of the reference carriers being an integer fraction of the sampling frequency on which the multiplex signal is based.
  • the sampling frequency is generated in a manner known per se in the radio receiver.
  • the following mixed signals result from multiplication with the values of the reference carrier sin (2w p t) or cos (2w p t) read from table 14:
  • ⁇ is the phase difference between the received pilot signal and a reference pilot signal generated from the sampling clock within the receiver. Elements with a higher frequency are not shown in equations (1) and (2), since they are later filtered out by the low-pass filters 10, 11.
  • the subsequent matrix circuit from the adders 8, 9 and the low-pass filters 10, 11 then generate the digital output signals L and R.
  • the low-pass filters can also be designed such that in addition to the suppression of the frequencies above the useful signal, the de-emphasis is carried out.
  • the generation of the correction signals G38c and G38s supplied to the multipliers 4 and 5 is first explained below with reference to FIG. 1.
  • the multiplex signal MPX first multiplied by two reference pilot signals sin (w p t) and cos (w p t), which are phase-shifted by 90 ° with respect to one another and are read from a table 16.
  • the output signals of these circuits are fed to the network 21, with the aid of which the correction signals G38s and G38c are derived. Before a description of the other parts of FIG. 1, the network 21 is described in more detail with reference to FIGS. 2 and 3.
  • the signals SPC1 and SPC2 supplied via the inputs 23, 24 are squared at 25, 26 and multiplied at 27.
  • the squared signals SPC1 and SPC2 are subtracted from each other at 28 and added at 29.
  • the product of the two signals is multiplied by "2" at 30, so that the following signals result:
  • the quantity A characterizes the amplitude of the received pilot signal and is converted with the aid of a subtractor 31 and a threshold value circuit 32 into a switching signal STI which can be taken from an output 33 and used to indicate stereo reception.
  • the signals F38c and F38s are freed from the component A with the aid of filters 34, 35, to which the signal A is also supplied, so that the influence of fluctuations in the amplitude of the pilot signal on the stereo decoding is eliminated.
  • the signals G38c and G38s freed from component A can Outputs 36, 37 are removed and fed to the multipliers 4, 5 (FIG. 1).
  • the number ⁇ can be fixed. However, it is also possible to vary the number ⁇ and thus the settling time, for example to carry out a short settling time corresponding to a high bandwidth of the filter immediately after a transmitter has been reset, which is then reduced to a lower bandwidth for the purpose of improving the signal-to-noise ratio.
  • Parts 50 to 59 of the circuit arrangement according to FIG. 1 represent a symmetry detector, the function of which is based on the fact that when the stereo multiplex signal is multiplied by a reference carrier which is quadrature to the carrier of the stereo difference signal, in the case no output signal is produced from sidebands with the same high amplitude.
  • a reference carrier which is quadrature to the carrier of the stereo difference signal
  • Such a signal is generated in any case in stereo decoders with quadrature demodulation of the carrier-frequency stereo difference signal, in which multiplication is carried out with two reference carriers which are phase-shifted by 90 ° and the phase position relative to the carrier is determined by a PLL circuit.
  • the signal obtained from the demodulation of the quadrature component can be fed directly to a low-pass filter 53, which is followed by a sampling rate conversion 54 around the divider 24. An amount is then formed at 55, whereupon the resulting signal SD1 is compared with a threshold value SDS at 56 and 57. At 58 the comparison result is evaluated in such a way that the signal ASD at the output 59 has the value 1 if the signal SD1 is greater than the threshold value SDS.
  • the signal processing described below is required before the low-pass filtering at 53.
  • the signal Imr1 is multiplied by the correction signal G38s.
  • the signal Imr2 is multiplied at 51 by the correction signal G38c.
  • the output signals of the multipliers 50, 51 are subtracted from one another at 52 and fed to the low-pass filter 53.
  • the signal ASD representing the reception quality can be used to switch from stereo to mono reception and can be supplied to the multiplier 7 instead of the signal D, for example.
  • other quantities can be used to form the signal D, such as the received field strength via the amplitude of the IF signal or spectral components in the multiplex signal above 60 kHz. These criteria can also be combined in a suitable manner, which is indicated in FIG. 1 in the form of a circuit 22.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Stereo-Broadcasting Methods (AREA)
  • Noise Elimination (AREA)

Abstract

Un circuit sert à dériver un signal de qualité dépendant de la qualité d'un signal multiplex de réception dans un récepteur radio stéréo. Le signal multiplex contient un signal d'addition (L+R) dans la bande de base, une porteuse auxiliaire modulée par un signal différentiel (L-R) et un signal pilote dont la fréquence équivaut à la moitié de la fréquence de la porteuse auxiliaire. Le signal multiplex numérique est multiplié par une porteuse de référence tirée d'une cadence de balayage générée dans le récepteur radio, en deux positions de phase mutuellement décalées de 90°. Les signaux mélangés produits par la multiplication sont multipliés chacun par un signal de correction, de manière à former des signaux mélangés corrigés qui sont additionnés et transmis avec le signal d'addition à un circuit matriciel afin de former les signaux audio stéréo (L, R). Les signaux mélangés sont en outre multipliés chacun par l'autre signal de correction. Les produits de ces multiplications sont soustraits l'un de l'autre et dirigés à travers un filtre passe-bas.

Claims (7)

  1. Procédé pour prélever dans un récepteur radio stéréo un signal de qualité fonction de la qualité d'un signal multiplex reçu, le signal multiplex contenant le signal de somme (L + R) dans la bande de base, une porteuse auxiliaire modulée avec un signal différentiel (L-R) et un signal pilote avec la demi fréquence de la porteuse auxiliaire, procédé dans lequel le signal multiplex (MPX) est multiplié (2, 3) sous forme numérique par une porteuse de référence (14), obtenue à partir d'un cycle de signaux de balayage produit dans le récepteur radio, dans deux positions de phase décalées à 90° l'une par rapport à l'autre,
    caractérisé en ce que
    les signaux composés provenant de la multiplication (Ims1, Ims2) sont multipliés respectivement par un signal de correction (G38c, G38s) en formant des signaux composés corrigés (Ims1, Ims2), les signaux de correction (G38c, G38s) étant prélevés du signal multiplex (MPX) en les multipliant par deux signaux pilotes de référence déphasés à 90°, en ce que les signaux composés corrigés (6) (Ims1, Ims2) sont additionnés, en ce que les signaux composés (Ims1, Ims2) sont multipliés (51, 50) par respectivement l'autre signal de correction (G38s, G38c), en ce que les produits (52) qui en résultent sont soustraits l'un de l'autre et filtrés dans un filtre passe-bas (53) et en ce qu'un signal de qualité est prélevé des produits filtrés par le filtre passe-bas.
  2. Procédé selon la revendication 1,
    caractérisé en ce que
    les signaux multipliés par les signaux pilotes de référence déphasés l'un par rapport à l'autre sont filtrés à travers un filtre passe-bas (17, 18) et en ce que les autres signaux composés qui en résultent ainsi (SPC1, SPC2) sont élevés au carré (25, 26) pour former le premier signal de correction (G38c) et sont soustraits l'un de l'autre (28) et sont multipliés (30) l'un par l'autre (27) et par la valeur 2 pour former le second signal de correction (G38s).
  3. Procédé selon la revendication 2,
    caractérisé en ce que
    les autres signaux (SPC1, SPC2) filtrés à travers un filtre passe-bas sont élevés au carré (25, 26) et additionnés (28, 29) pour former un signal représentant l'amplitude du signal pilote.
  4. Procédé selon la revendication 3,
    caractérisé en ce que
    les signaux (F38s, F38c) produits selon la revendication 2 sont modifiés à l'aide du signal représentant l'amplitude (A) du signal pilote dans le sens d'une normalisation de leur amplitude (34, 35).
  5. Procédé selon l'une des revendications précédentes,
    caractérisé en ce que
    on réalise une formation de la valeur absolue (55) après le filtre passe-bas (53).
  6. Procédé selon la revendication 5,
    caractérisé en ce que
    la formation de la valeur absolue est réalisée sous la forme d'une élévation au carré.
  7. Procédé selon l'une des revendications 5 ou 6,
    caractérisé en ce que
    la valeur absolue formée (55) est comparée à une valeur de seuil (57) et le résultat de la comparaison (58) est délivré en tant que signal de qualité (ASD).
EP94911061A 1993-03-24 1994-03-22 Methode pour la derivation d'un signal de qualite dependant de la qualite d'un signal multiplex de reception Expired - Lifetime EP0691049B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4309518A DE4309518A1 (de) 1993-03-24 1993-03-24 Schaltungsanordnung zur Ableitung mindestens eines von der Qualität eines empfangenen Signals abhängigen Qualitätssignals
DE4309518 1993-03-24
PCT/DE1994/000320 WO1994022228A1 (fr) 1993-03-24 1994-03-22 Circuit pour la derivation d'un signal de qualite dependant de la qualite d'un signal multiplex de reception

Publications (2)

Publication Number Publication Date
EP0691049A1 EP0691049A1 (fr) 1996-01-10
EP0691049B1 true EP0691049B1 (fr) 1997-06-11

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EP94911061A Expired - Lifetime EP0691049B1 (fr) 1993-03-24 1994-03-22 Methode pour la derivation d'un signal de qualite dependant de la qualite d'un signal multiplex de reception

Country Status (5)

Country Link
US (1) US5696830A (fr)
EP (1) EP0691049B1 (fr)
JP (1) JP3640669B2 (fr)
DE (1) DE59403123D1 (fr)
WO (1) WO1994022228A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19630395C1 (de) * 1996-07-26 1997-10-02 Sgs Thomson Microelectronics Elektrische Stummsteuerschaltung
US20030087618A1 (en) * 2001-11-08 2003-05-08 Junsong Li Digital FM stereo decoder and method of operation
WO2006077761A1 (fr) * 2005-01-24 2006-07-27 Pioneer Corporation Generateur de signal de sous-porteuse et demodulateur de signal multiplexe
JP4916974B2 (ja) * 2007-08-03 2012-04-18 オンセミコンダクター・トレーディング・リミテッド Ｆｍチューナ

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4630299A (en) * 1985-02-22 1986-12-16 General Electric Company Digital circuit for decoding digitized, demodulated FM stereo signals
DE4027399C2 (de) * 1990-08-30 1995-11-30 Blaupunkt Werke Gmbh UKW-Autoradio
DE4241362C2 (de) * 1992-12-09 1997-06-05 Blaupunkt Werke Gmbh Rundfunkempfänger
DE4303387A1 (de) * 1993-02-05 1994-08-11 Blaupunkt Werke Gmbh Schaltungsanordnung zur Decodierung eines Multiplexsignals in einem Stereo-Rundfunkempfänger

Also Published As

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WO1994022228A1 (fr) 1994-09-29
DE59403123D1 (de) 1997-07-17
JPH08508142A (ja) 1996-08-27
JP3640669B2 (ja) 2005-04-20
EP0691049A1 (fr) 1996-01-10
US5696830A (en) 1997-12-09

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