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Coherent, fixed BAUD rate FSK communication method and apparatus

  • US 3,924,065 A
  • Filed: 04/05/1974
  • Issued: 12/02/1975
  • Est. Priority Date: 04/05/1974
  • Status: Expired due to Term
First Claim
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1. A frequency shift key (FSK) communication apparatus for communicating time division binary message codes comprising a predetermined number of message bits, having logic levels representing logical '"'"''"'"''"'"''"'"'ones'"'"''"'"''"'"''"'"' and logical '"'"''"'"''"'"''"'"'zeros'"'"''"'"''"'"''"'"', from a transmitter station to a receiver station, the apparatus comprising:

  • a digital encoder in the transmitter station, having a predetermined message code comprising a predetermined number (N) message bits, generating at least two output signal levels for each message bit of the N-bit message code at a digital encoder output signal;

    an FSK generator in the transmitter station receiving the digital encoder output signal and providing an output signal having a distinct frequency in response to each received digital encoder output signal level, the FSK generator output signal having a fixed transmission time for the (N) bit message code independent of the number of logical '"'"''"'"''"'"''"'"'ones'"'"''"'"''"'"''"'"' and logical '"'"''"'"''"'"''"'"'zeros'"'"''"'"''"'"''"'"' comprising the (N) bit message code;

    means in the transmitter station receiving the FSK generator output signal and providing a transmitter master clock signal derived from the received FSK generator output signal and having a frequency coherently related to the FSK generator output signal frequency, the transmitted master clock signal being connected to the digital encoder and operating the digital encoder to provide the digital encoder output signal in one condition of the digital encoder;

    means in the transmitter station receiving and transmitting the FSK generator output signal;

    means in the receiver station receiving the transmitted FSK generator output signal and providing an output signal corresponding to the received FSK generator output signal;

    means in the receiver station receiving the output signal corresponding to the transmitted FSK generator output signal and providing a receiver master clock signal derived from the received FSK generator output signal and having a frequency coherently related to the FSK generator output signal frequency; and

    means in the receiver station receiving the receiver master clock signal, receiving the output signal corresponding to the transmitted FSK generator output signal and decoding the transmitted FSK generator output signal to derive the transmitted message code, the receiveR master clock signal providing the receiver master clock signal pulses for decoding the transmitted FSK generator output signal at a frequency coherently related to the frequency of the transmitter master clock signal.

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