VERFAHREN UND EINRICHTUNG ZUM FESTSTELLEN DES AUFTRETENS EINER ERWARTETEN DIGITALEN SIGNALFOLGEART

• Main Author: CARMEL FIORINO,BENJAMIN
• Format: Patent
• Language: German
• Published: 04.07.1974
• Subjects: BASIC ELECTRONIC CIRCUITRY; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; INFORMATION STORAGE; INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORDCARRIER AND TRANSDUCER; PHYSICS; PULSE TECHNIQUE; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

The base frequency of digital data signal is detected by using the transitions in the digital signal to control the duration of ramp signals generated by ramp generators. One ramp is restarted by each positive transition while a second ramp is restarted by each negative transition. Comparators monitor each ramp and compare the ramp against a threshold level. The threshold is set so that the comparator will change its state of output at a time period T=1/2f where f is the base frequency of the expected data signal. The outputs from the two comparators are exclusive-OR'd to produce a signal whose duration is a measure of the frequency departure of the input data signal from the expected data frequency. The output of the exclusive-OR is integrated to obtain an average DC voltage level which is a measure of the frequency of the input data signal. This average DC level varies linearly with the departure of the input data frequency from the expected data frequency. The output of the integrator is compared against a threshold by a comparator. This comparator generates an output signal indicating when the frequency of the input data signal is approaching the expected data frequency, i.e., the condition of beginning of record or beginning of data block. The threshold used by this last comparator may be adjusted to change the selectivity or bandwidth of frequencies that will result in the apparatus detecting the beginning of a data record.