High speed frequency-shift keying decoder
AssigneeFord Motor Company
InventorsJohn F. Kennedy, Robert D. Plowdrey
Life of this patent
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Abstract
A frequency-shift keying (FSK) signal detector splits an FSK signal into two paths. In one path, a phase-altering circuit having a variable frequency characteristic between the two encoding frequencies of the FSK signal provides either a phase lead or a phase lag depending upon the instantaneous frequency of the FSK signal. The phase-altered signal is sampled in response to the signal in the second path to decode a digital signal.
Claims8
Apparatus for decoding a frequency-shift keying (FSK) signal which modulates between a first frequency f.sub.1 and a second frequency f.sub.2 to encode digital information, comprising:
- wave-shaping means for shaping said FSK signal to generate substantially identical first and second wave-shaped signals;
- an LC tank circuit receiving said first wave-shaped signal for generating a phase-altered signal, said LC tank circuit having a resonant frequency f.sub.0 between said first frequency f.sub.1 and said second frequency f.sub.2 ;
- and
- sampling means for sampling one of said phase-altered signal or said second wave-shaped signal in response to a transition in the other one of said phase-altered signal or said second wave-shaped signal to generate a decoded signal.
A method for decoding a frequency-shift keying (FSK) signal which modulates between a first frequency f.sub.1 and a second frequency f.sub.2 to encode digital information, comprising the steps of:
- generating substantially identical first and second wave-shaped signals in response to said FSK signal;
- phase-altering said first wave-shaped signal to generate a phase-altered signal either leading or lagging said second wave-shaped signal depending on whether said first wave-shaped signal exhibits said frequency f.sub.1 or said frequency f.sub.2 by coupling said first wave-shaped signal to an LC tank circuit having a resonant frequency f.sub.0 between said first frequency f.sub.1 and said second frequency f.sub.2 ;
- and
- sampling one of said phase-altered signal or said second wave-shaped signal in response to a transition in the other one of said phase-altered signal or said second wave-shaped signal to generate a decoded signal.
Apparatus for decoding a frequency-shift keying (FSK) signal which modulates between a first frequency f.sub.1 and second frequency f.sub.2 to encode digital information, comprising:
- a first signal path receiving said FSK signal including the series connection of a first amplifier, an LC tank circuit, and a second amplifier to generate a phase-altered signal, said LC tank circuit having a resonant frequency f.sub.0 between said first frequency f.sub.1 and said second frequency f.sub.2 ;
- a second signal path receiving said FSK signal including the series connection of a third amplifier and a fourth amplifier to generate a reference signal;
- and
- a flip-flop responsive to said phase-altered signal and said reference signal to generate a decoded signal representing said digital information.
Dependencies are inferred from the claim text.