Electrical audio signal processing systems and devices – Binaural and stereophonic – Broadcast or multiplex stereo
Patent
1995-08-25
1997-12-09
Kuntz, Curtis
Electrical audio signal processing systems and devices
Binaural and stereophonic
Broadcast or multiplex stereo
381 7, H04H 500
Patent
active
056968302
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a circuit arrangement for deriving a quality signal, dependent on the quality of a received multiplex signal, in a stereo broadcast receiver, the multiplex signal containing a sum signal (L+R) in the base band, a subcarrier modulated with a difference signal (L-R) and a pilot signal having half the frequency of the subcarrier.
In the case of car radios, in particular, the quality of reception can fluctuate strongly--for example, owing to dips in the received field strength, owing to multipath reception or owing to the reception of interference signals. In order to keep the disturbances thereby produced as small as possible, various methods are known for masking these disturbances in the LF signal. Thus, it is possible, for example, in the case of poor reception to attenuate the LF signal temporarily, or to reduce the stereo channel separation. These known measures assume, however, that the signal quality can be determined correctly.
SUMMARY OF THE INVENTION
It is the object of the present invention to specify a circuit arrangement for deriving at least one quality signal dependent on the quality of a received signal.
This object is achieved according to the invention when the multiplex signal in digital form is multiplied by a reference carrier, obtained from a scanning rate generated in the broadcast receiver, in two phase angles mutually shifted by 90.degree., the mixed signals produced by the multiplication are each multiplied by a correction signal to form corrected mixed signals, the corrected mixed signals are added and fed together with the sum signal to a matrix circuit in order to form stereo audio signals (L, R), the mixed signals are further multiplied by the respective other correction signal, and the products of these multiplications are subtracted from one another and subjected to lowpass filtering.
The circuit arrangement according to the invention permits the detection of audible disturbances and is based on the evaluation of the symmetry of the stereo difference signal at subcarrier frequency. It is essential in this procedure that an undisturbed signal must be symmetrical relative to the carrier because of the double sideband amplitude modulation. In the circuit arrangement according to the invention, this symmetry is guaranteed in the case of an undisturbed signal by means of in-phase feeding of the sidebands to be compared. An asymmetry therefore permits the conclusion that there is a disturbance which is audible in the LF signal.
One feature of the invention contributes to symmetry in the undisturbed case in an advantageous way owing to the fact that to form the correction signals the multiplex signal is multiplied by a reference pilot signal, phase-coupled to the reference carrier, in two phase angles mutually shifted by 90.degree., the further mixed signals produced are subjected to lowpass filtering, and for the purpose of forming the first correction signal the lowpass-filtered, further mixed signals are squared and subtracted from one another and, for the purpose of forming the second correction signal, are multiplied, by one another and by two.
The effect of a fluctuation, not relevant for the purposes of the circuit arrangement according to the invention, in the amplitude of the pilot signal can be suppressed by providing that the lowpass-filtered, further mixed signals are squared and added for the purpose of forming a signal representing the amplitude of the pilot signal, and that the correction signals are controlled with the aid of the signal representing the amplitude of the pilot signal for the purpose of standardizing their amplitude.
In general, the direction of the asymmetry of the sidebands is not important, and so an absolute value generation is provided downstream of the lowpass filter. This is preferably performed by squaring.
The quality signal derived using the circuit arrangement can by all means be an analog signal, which can assume intermediate values between two limiting values. For many purposes, howeve
REFERENCES:
patent: 4630299 (1986-12-01), Welles, II et al.
patent: 5222252 (1993-06-01), Kasser
patent: 5442709 (1995-08-01), Vogt et al.
patent: 5483694 (1996-01-01), Bartels et al.
Chahabadi Djahanyar
Herrmann Matthias
Kaesser Jurgen
Vogt Lothar
Kuntz Curtis
Lee Ping W.
Robert & Bosch GmbH
Striker Michael J.
LandOfFree
Circuit arrangement for deriving a quality signal dependent on t does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Circuit arrangement for deriving a quality signal dependent on t, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circuit arrangement for deriving a quality signal dependent on t will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1614244