Self-synchronizing Bi-orthogonal Coded PCM Telemetry SystemThis report describes the complete design, theory, and experimental statistics of a self-synchronizing, biorthogonal coded PCM telemetry system for space communications. By selecting a proper code set, word synchronization is acquired without using a parallel channel and is maintained at a signal-to-noise ratio below 4 db. With the code's property of comma freedom, word synchronization can be achieved with a circuit requiring only a few logic modules. With the use of this circuit, signal detection can be performed in real time without the use of a computer. The measured probability of word error correspond to a signal-to-noise that is within 1 db of theoretical predictions; this is 3 db better than is obtain with the standard PCM systems now used on spacecraft. |
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ADDER analog signal bandwidth bi-orthogonal code set binary Bode plot circuit code words comma freedom comma-freedom-of-two property communication channel confidence factor correct phase correlation value correlator output data word decoding detected data determined Digilock code sets digit clock digit conditioner digit period diode EXCEEDING THRESHOLD filter gaussian noise given threshold Goddard Space Flight in-phase index of comma information bits input Kronecker product logic LOW-PASS FILTER maximum correlation level maximum likelihood detector modulo-two noise-free correlation number of digit orthogonal code orthogonal matrix out-of-phase positions p₁ performed phase-lock loop PROBABILITY OF EXCEEDING probability of word proper code set R₁ R₂ RECEIVED SIGNAL Reed-Muller code resistors SCALER self-synchronization property shown in Figure signal-to-noise ratio Space Flight Center spacecraft Stiffler code set Stiffler modifying code storage unit stored replicas synchronization statistics threshold level transition detector transmitted code volts Warner Miller WORD CLOCK word error word period word synchronization