FSK DEMODULATION CIRCUIT AND FREQUENCY RETENTION CIRCUIT
PURPOSE:To make the device small in size and low in cost by eliminating the need for an oscillator with high precision for discrimination of a frequency component of an FSK signal. CONSTITUTION:This circuit is provided with a counter 32 counting number of oscillated pulses from a self-oscillation ci...
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Format: | Patent |
Sprache: | eng |
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Zusammenfassung: | PURPOSE:To make the device small in size and low in cost by eliminating the need for an oscillator with high precision for discrimination of a frequency component of an FSK signal. CONSTITUTION:This circuit is provided with a counter 32 counting number of oscillated pulses from a self-oscillation circuit 31, a latch circuit 33 storing a count for one period of a reference signal in the counter 32 as a reference pulse number, and a comparator circuit 34 comparing the count of the counter 32 with the reference pulse number stored in the latch circuit 33 and outputting a coincidence signal when they are coincident and the count of the counter 32 is cleared in a rising timing of an FSK signal. Thus, when one period of the FSK signal is longer than one period of the reference signal, the comparator circuit 34 outputs the coincidence signal and when shorter, no coincidence signal is outputted. The frequency component of the FSK signal is discriminated based on the presence/absence of the coincidence signal. |
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