Dropout detecting circuitry for a frequency modulated carrier, particularly for a video recorder
First Claim
1. In a dropout detecting circuit for a frequency modulated carrier, particularly for a video recorder, in which the carrier is modulated over a definite frequency deviation range and is demodulated in an FM detector whose output voltage is used in an evaluation circuit to produce a switching pulse representing the dropout, the improvement comprising, in combination, a demodulator constituting said FM detector and providing a digital output signal having a first value within such deviation range of the carrier and a second value outside such deviation range;
- and an evaluation circuit connected to said demodulator and producing said switching pulse responsive to only said second value of such digital output signal, said demodulator comprising a re-triggerable monoflop having a control input and an output; and
an edge-triggered D flip-flop having first and second control inputs and having outputs;
said FM carrier being applied to the control input of said retriggerable monoflop and to said first input of said edge-triggered D flip-flop;
said output of said retriggerable monoflop being connected to said second control input of said D flip-flop;
such switching pulse being derived at one of the outputs of said D flip-flop.
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Accused Products
Abstract
The carrier is modulated over a definite frequency deviation range and is demodulated in an FM detector whose output voltage is used in an evaluation circuit to produce a switching pulse representing the dropout. The FM detector is constituted by a demodulator providing a digital output signal having a first value "1" within the deviation range and a second value "0" outside the deviation range. An evaluation circuit is connected to the demodulator and produces the switching pulse responsive to only the second value "O". The demodulator includes an retriggerable monoflop and an edge-triggered D flip-flop, and the FM carrier is supplied to the control input of the retriggerable monoflop and to a first control input of the edge-triggered D flip-flop. One output of the monoflop is connected to a second control input of the D flip-flop and the switching pulse is provided at one of the outputs of the D flip-flop. Two such demodulators may be used, and have unequal pulse durations at the outputs of the respective monoflops and have their outputs connected to the inputs of an AND stage whose output voltage serves as the switching pulse.
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Citations
6 Claims
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1. In a dropout detecting circuit for a frequency modulated carrier, particularly for a video recorder, in which the carrier is modulated over a definite frequency deviation range and is demodulated in an FM detector whose output voltage is used in an evaluation circuit to produce a switching pulse representing the dropout, the improvement comprising, in combination, a demodulator constituting said FM detector and providing a digital output signal having a first value within such deviation range of the carrier and a second value outside such deviation range;
- and an evaluation circuit connected to said demodulator and producing said switching pulse responsive to only said second value of such digital output signal, said demodulator comprising a re-triggerable monoflop having a control input and an output; and
an edge-triggered D flip-flop having first and second control inputs and having outputs;
said FM carrier being applied to the control input of said retriggerable monoflop and to said first input of said edge-triggered D flip-flop;
said output of said retriggerable monoflop being connected to said second control input of said D flip-flop;
such switching pulse being derived at one of the outputs of said D flip-flop. - View Dependent Claims (2, 3, 4, 5, 6)
- and an evaluation circuit connected to said demodulator and producing said switching pulse responsive to only said second value of such digital output signal, said demodulator comprising a re-triggerable monoflop having a control input and an output; and
Specification