JPS56764A - Fsk modulation system - Google Patents

Abstract

PURPOSE:To increase the reliability of data transmission, by avoiding the discontinuity of phase at the switching point of input data, by obtaining the FSK modulation signal after the synchronism of the input data with the signals in frequencies f1, f2 and also with the FSK modulation output signal. CONSTITUTION:The input data a is formed into the signal (e) taking synchronism with the FSK modulation output signal (b) at the FF circuit 4. This signal (e) is taken with the synchronism with the signal (c) in frequency f1 at the FF circuit 5, and the signal (h) output from the gate circuit 9 starts the pulse with a delay in the maximum T1=1/f1 from the rising point of the signal (e) and the pulse is stopped at the trailing of the signal (e). On the other hand, the output signal (e) is synchronized with the signal (d) in frequency f2 at the FF circuit 6, and the signal (i) from the gate circuit 10 starts the pulse with a delay of maximum T2=1/f2 from the trailing point of the signal (e) and the pulse stops at the leading of the signal (e). FSK modulation signal (b) is obtained by passing through the signals h, i to the gate circuit 11. This signal (b) has the region in continuous with 1, 0 levels at the switching point of the input data (a).