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A digital frequency discriminator processes input pulses including first and second time separated input pulses to determine if the frequency of any two sequential pulses lie within a predetermined frequency band with upper and lower frequency limits and that they are received for at least a predete

A digital frequency discriminator processes input pulses including first and second time separated input pulses to determine if the frequency of any two sequential pulses lie within a predetermined frequency band with upper and lower frequency limits and that they are received for at least a predetermined period of time. A delay timer is coupled to sense the input pulse stream and operates in a pulse sensing standby mode prior to receipt of the first input pulse. Upon receipt of the first input pulse, the delay timer switches into a time-limited active mode to define a fixed duration delay interval having a duration equal to the period of the upper frequency limit of the frequency band. The delay timer switches back into the pulse sensing standby mode upon completion of the delay interval. A gate timer is coupled to the output of the delay timer and switches from a standby mode into a time-limited active mode upon completion of the delay interval to define a fixed duration bandwidth interval. A monitoring circuit includes a first input coupled to monitor the input pulse stream and a second input coupled to monitor the output of the gate timer. The monitoring circuit generates a frequency coincidence signal when the second input pulse is received during the bandwidth interval to indicate that the frequency of the input pulse lies within the predetermined frequency band. A recognition circuit is coupled to monitor the output of the coincidence detector to ensure that the coincidence signal is received for at least a predetermined period of time.

대표청구항 ▼

A signal-synchronized digital frequency discriminator for digitally processing an optical input signal including first and second time separated optical input pulses to determine if the frequency of any two sequential pulses lies within a predetermined frequency band with upper and lower frequency l

A signal-synchronized digital frequency discriminator for digitally processing an optical input signal including first and second time separated optical input pulses to determine if the frequency of any two sequential pulses lies within a predetermined frequency band with upper and lower frequency limits, comprising: a. an optical signal detector circuit for receiving the optical input signal consisting of a series of spaced-apart optical pulses and for generating an electrical output signal including output pulses synchronized with the optical input pulses; b. a delay timer having a pulse detector coupled to sense the output pulses from the optical signal detector for operating in a pulse sensing standby mode prior to receipt of the first pulse, for switching into a time-limited active mode upon receipt of the first pulse to define a fixed duration delay interval having a duration equal to the period of the upper frequency limit of the frequency band, and for switching back into the pulse sensing standby mode upon completion of the delay interval; c. a gate timer coupled to an output of the delay timer for switching from a standby mode into a time-limited active mode upon completion of the delay interval to define a fixed duration bandwidth interval; and d. a monitoring circuit having a first input coupled to the pulse detector to monitor the pulses and a second input coupled to monitor an output of the gate timer for generating a frequency coincidence signal when the second pulse is received during the bandwidth interval to indicate that the frequency of the optical input pulses lies within the predetermined frequency band.