DOUBLE FREQUENCY-SHIFT KEY DEMODULATION STUDY.
Final rept., 4 Apr 62-30 June 63.
PAGE COMMUNICATIONS ENGINEERS INC WASHINGTON D C
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The continued investigation of an improved technique for the detection of received signals in double frequency-shift keying systems is reported on. Under an earlier RADC contract, a variable decision technique was applied to an experimental DFSK demodulator and, in controlled tests, achieved a substantial reduction in teleprinter errors during frequency selective fading. To realize more fully the performance potential of the experimental demodulator under operational conditions, a tuning indicator and automatic alarm system were added, and the decision logic was refined and simplified. A rigorous theoretical analysis of optimum performance characteristics confirmed and validated earlier test results. Actual performance was tested over a 2500-mile radio path in comparison with a conventional DFSK system. In singlediversity operation, the experimental demodulator performed as well as the conventional system in dual diversity. With both systems in single diversity, it appeared to outperform the conventional demodulator by about 40 to 1 in error rate. Author