Derived clock from carrier envelope

Abstract

Abstract DIGITAL DATA TRANSMISSION AT VERY HIGH BIT RATES THROUGH RANDOMLY SELECTED ORDINARY VOICE-GRADE TELEPHONE LINES BY THE USE OF A TRANSMITTER WHICH INCLUDES DIGITAL DIFFERENTIAL MODULATION AND A RECEIVER WHICH INCLUDES A DIGITAL DIFFERENTIAL ANGLE DEMODULATION, TOGETHER WITH A DERIVED CLOCK CIRCUIT AT THE RECEIVER, IS DISCLOSED. THE COMMUNICATION LINK INCLUDES BANDPASS FILTERS WHICH BLOCK SIDEBAND FREQUENCIES LOCATED AT 1/T FROM THE CENTERPOINT, FO, OF THE FILTER, WHEREIN T IS THE MODULATION PERIOD, AND FO IS THE CARRIER FREQUENCY. FOR RANDOM DATA PATTERNS, THE ENVELOPE AT THE RECEIVER, DUE TO BAND-LIMITING, IS PEAKED AT THE MIDDLE OF A CENTER MODULATION PERIOD AND DROPS SUFFICIENTLY TOWARD ZERO AMPLITUDE BETWEEN MODULATION PERIODS SO AS TO CONTAIN STRONG 1/T HARMONICS WHICH PROVIDE FOR CLOCK DERIVATION BY SLAVING A LOCAL OSCILLATOR WITH A 1/T OUTPUT SIGNAL. FOR SOME NON-VARYING DATA PATTERNS, THE ENVELOPE DOES NOT INCLUDE SUFFICIENT RIPPLE FOR CLOCK DERIVATION. AMPLITUDE MODULATION OF THE DIGITAL ANGLE MODULATION SIGNAL AT A PREDETERMINED FREQUENCY IS PROVIDED AT THE TRANSMITTER SO AS TO PRODUCE A SIGNAL HAVING 1/2T SIDEBANDS WHICH ARE PASSED BY THE FILTER AND THUS ARE AVAILABLE AT THE RECEIVER FOR CLOCK DERIVATION.

Inventors

• 👤 Sang Y Whang
• 👤 Paul E Payne
• 👤 Robert G Ragsdale

Bibliographic Details