Apparatus and method for search tuning of satellite television sound carriers
AssigneeDeutsche ITT Industries GmbH
InventorsThomas Hilpert, Stefan Mueller
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Abstract
Apparatus and method for frequency-tuning the frequency-modulated sound carriers of multichannel sound transmission signals in a satellite television receiver. By utilizing digital signal processing, the audio range of the television satellite channel is searched for the desired sound carrier in steps. Then the FM center frequency is determined by calculating the average amplitude density in each measurement interval.
Claims20
Apparatus for use with a television receiver having frequency modulated sound carriers of multichannel sound transmission standards suitable for television satellite reception using a digital sound processing section for frequency tuning said television receiver, said television receiver including a quadrature mixer, a channel filter having an output, a demodulator coupled to said output, a sound stage and a central control unit which continuously tunes said quadrature mixer by utilizing a frequency programmable digital generator, comprising:
- tuning means coupled to said generator for frequency tuning by use of an automatic search control where the frequency of a heterodyne signal pair is changed in steps and each search tuning frequency step represents a measurement interval;
- filter switching means coupled to said channel filter for switching the passband of said channel filter by said central control unit to a bandwidth lying between twice and five times the bandwidth of said search tuning frequency step;
- demodulator switching means coupled to said demodulator for switching by said central control unit to amplitude demodulation;
- extreme value detection means coupled to an evaluating device and a display device for determining a relative maximum value of an amplitude from adjacent measurement intervals, wherein said relative maximum value is provided to said evaluating device and said display device and is assigned to an associated search tuning frequency step by said central control unit.
Method for use with a television receiver having frequency modulated sound carriers of multichannel sound transmission standards suitable for television satellite reception using a digital sound processing section for frequency tuning said television receiver, said television receiver including a quadrature mixer, a channel filter having an output, a demodulator coupled to said output, a sound stage and a central control unit which continuously tunes said quadrature mixer by utilizing a frequency programmable digital generator, comprising the steps of:
- frequency tuning by use of an automatic search control the frequency of a heterodyne signal pair provided by a generator in steps wherein each search tuning frequency step represents a measurement interval;
- switching the passband of a channel filter by a central control unit to a bandwidth lying between twice and five times the bandwidth of said search tuning frequency step;
- changing a demodulator to amplitude demodulation by said central control unit;
- determining a relative maximum value of an amplitude from adjacent measurement intervals, wherein said relative maximum value is provided to an evaluating device and a display device and is assigned to an associated search tuning frequency by said central control unit.
Dependencies are inferred from the claim text.