1975-05-21
1977-01-18
Murray, Richard
325464, 325469, H04B 116
Patent
active
040042316
ABSTRACT:
A circuit arrangement for automatic fine tuning of a broadcast receiver to an assigned transmission frequency. The receiver has an input stage which can be tuned over a desired receiving frequency range by a variable control voltage fed to the input stage. The input stage feeds a discriminator having an S-shaped output signal characteristic and producing an output signal having a given nominal value when the input stage is tuned to the assigned frequency. A first variable frequency clock generator is controlled by a control signal depending on the output signal of the discriminator and feeds an up/down counter the count of which is converted by a digital-analog converter into the control voltage for the input stage. The first clock generator is so designed that its output signal frequency varies constantly in dependence on the deviation of the discriminator output signal from the nominal value, and that it has a zero value when the discriminator output signal has the nominal value. The first clock generator operates the counter only when the input stage has become tuned to a frequency within a certain range of the selected frequency. Outside this range, the counter is clocked by a fixed high frequency clock generator. An image frequency detector is connected to the discriminator output for generating a disabling signal when the input stage is tuned to an image frequency, the disabling signal being applied to prevent switching from the fixed frequency clock generator to the variable frequency clock generator.
REFERENCES:
patent: 3649919 (1972-03-01), Fridman
patent: 3903433 (1975-09-01), Leuschner
patent: 3916179 (1975-10-01), Cuzzo
Elshuber Karl
Gotz Laszlo
Comfort James T.
Donaldson Richard L.
Levine Harold
Masinick Michael A.
Murray Richard
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