Coded or modulated digital data converts to nonreturn to zero /NRZ/ data. Technique includes logic implementation and pertinent timing diagrams. Demodulation to NRZ facilitates digital logic operations on incoming data. Phase-delay modulation has advantage of inherent self-timing not present in NRZ modulation

Lewin, J.

English

NASA Technical Reports Server

September 1971	 Brief 71-10345 
NASA TECH BRIEF 
Goddard Space Flight Center 
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NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a aubscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Digital Decoder for Phase-Delay Coded Data 
fl
A digital decoding technique can be used to 
convert "phase-delay" coded or modulated digital 
data to nonreturn to zero (NRZ) data. The technique 
includes logic implementation and pertinent timing 
diagrams. Demodulation to NRZ facilitates digital 
logic operations on incoming data. 
Phase-delay modulation, originally developed in 
conjunction with high-density (saturation) digital 
tape recording, combines the advantages of both 
NRZ and phase modulation. Unlike phase modula-
tion, which has two transitions per bit at the 
maximum character rate, phase-delay modulation 
requires at most one transition per bit and thus 
permits a higher packing density. Consequently, 
though phase-delay modulation requires approximately 
the same bandwidth as NRZ modulation, it has the 
advantage of inherent self-timing not present in 
NRZ modulation. 
A potential time-phase ambiguity exists in re-
ceiving and decoding phase-delay data when the 
timing information is extracted from the transitions 
in the incoming data bits. A clock phase shift of ir 
radians (1800) can occur when the receiver syn-
chronizes to the "wrong" (half-a-bit out of phase) 
transitions. Proper phasing of the receiver clock and 
data must be ensured at all times for reliable de-
coding operation.
Although operation of the decoder in converting 
phase-delay data to NRZ, as well as tracking the 
correct phase, has been confirmed in the laboratory, 
its quantitative performance under severe noise condi-
tions has not yet been evaluated. Under such condi-
tions, it may be necessary to include coding or error 
detection techniques to augment the phase-tracking 
circuitry. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: TSP71-10345 
Patent status: 
No patent action is contemplated by NASA. 
Source: J. Lewin of
Astro-Electronics Div. 
Radio Corp. of America

under contract to 
Goddard Space Flight Center 
(G SC- 10894) 
Category 01 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19710000343 2020-03-17T02:28:17+00:00Z


Digital decoder for phase-delay coded data

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