Electrical audio signal processing systems and devices – Binaural and stereophonic – Broadcast or multiplex stereo
Patent
1995-08-25
1997-08-26
Kuntz, Curtis
Electrical audio signal processing systems and devices
Binaural and stereophonic
Broadcast or multiplex stereo
381 10, H04H 500
Patent
active
056618107
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a circuit arrangement for deriving signals for masking audio signals in a broadcast radio receiver.
Particularly in the case of automobile radios, the reception quality can fluctuate severely as a result of glitches in the received field strength. In order to keep the interference caused by this as low as possible, measures are known for masking this interference in audio signals. For example, if the received field strength is low, it is thus possible to reduce the stereo channel isolation or to temporarily attenuate the audio signals.
SUMMARY OF THE INVENTION
The object of the present invention is to specify a circuit arrangement for a broadcast radio receiver, in particular for an automobile radio having digital signal processing, by means of which suitable signals for masking the audio signals are produced.
According to the invention, the circuit arrangement for deriving masking signals for masking audio signals in a broadcast radio receiver includes a first low-pass filter means for filtering an input signal substantially proportional to a received field strength in the radio receiver to form a first low-pass filter output signal; a second low-pass filter means for filtering the input signal to form a second low-pass filter output signal; a first weighting circuit means for weighting the first low-pass filter output signal of the first low-pass filter means with first coefficients to form a first weighted output signal; means for forming a masking signal for reducing stereo channel isolation from the first weighted output signal of the first weighting circuit means; second weighting circuit means for forming a second weighted output signal from the first low-pass filter output signal or the second low-pass filter output signal with second coefficients according to a switching signal indicative of the presence of interference in the audio signals; switching means for selecting the first low-pass filter output signal for weighting in the second weighting circuit means when no interference is indicated by the switching signal and the second low-pass filter output signal for weighting in the second weighting circuit means when interference is indicated by the switching signal; and means for forming a masking signal for damping the audio signal from the second weighted output signal of the second weighting circuit means.
The circuit arrangement according to the invention has the advantage that the signals which are produced can be matched to the masking which is respectively to be carried out so that an intervention, which is carried out by the masking, in the audio signals does not cause further audible interference, as far as possible.
In the case of an advantageous embodiment it is provided that the masking is carried out by attenuation of the audio signals and that the predetermined function contains a linear component and a constant component, each having a coefficient which is stored in a memory. At the same time, it is preferably provided that the weighted signal which is proportional to the field strength is limited to a maximum value.
Another advantageous embodiment comprises the masking being carried out by a reduction in the stereo channel isolation, the weighting being carried out by multiplication by a coefficient which is stored in a memory.
Although, in the case of the circuit arrangement according to the invention, the coefficients can also be permanently stored, a development of the invention is particularly advantageous in that the coefficient or coefficients is or are stored in a non-volatile memory and can be varied with the aid of a microcomputer, a display device and a control device and with the aid of a program for operator guidance.
As a result of this development, it is possible to match individual items in a large batch of broadcast radio receivers to different operational conditions which may, for example, be typical of a state. It can also be made possible for a service workshop or even the user to vary the coefficients.
A
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Chahabadi Djahanyar
Herrmann Matthias
Kaesser Jurgen
Vogt Lothar
Chang Vivian
Kuntz Curtis
Robert & Bosch GmbH
Striker Michael J.
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