Decision network for receiver of PSK digital signals

Details Decision network for receiver of PSK digital signals Decision network for receiver of PSK digital signals

1976-03-25

1978-02-28

Griffin, Robert L.

Telegraphy

Code transmitters

Rotary contact

325320, 178 67, H04L 1524

Patent

active

040769569

ABSTRACT:
In a phase-shift-keying (PSK) signaling system with or without amplitude modulation, using two channel carriers of like frequency in relative phase quadrature to identify one of eight signal levels, each signal level is associated with one of eight equispaced radii emanating from the center of an orthogonal matrix or coordinate system. That matrix is divided by its coordinate axes into four quadrants each encompassing three zones of potential signal deviation, i.e. a middle zone centered on the bisector of the quadrant and two lateral zones whose outer boundaries coincide with those of the quadrant. The signals incoming at a receiver input over the two channels are coherently detected and filtered to supply a pair of coordinates defining a point on the matrix generally falling into one of the three zones of a quadrant; upon conversion into digital form, with six modular bits and one sign bit each, these signals by their modular bits address one of 4,096 cells of a first read-only memory to call forth one of three two-bit combinations stored in these cells. The bit combination so read out identifies the zone -- irrespective of quadrant -- defined by the detected coordinates; these bits, together with the sign bits derived from the incoming signals, address one of 12 cells in a second read-only memory which thereupon delivers a three-bit word indicating the corresponding signal level and, if desired, two collateral multibit words fed back to the receiver input for correcting distortions of the next-following signals.

REFERENCES:
patent: 3706945 (1972-12-01), Yanagidaira
patent: 3805191 (1974-04-01), Kawai
patent: 3818346 (1974-06-01), Fletcher
patent: 3845412 (1974-10-01), Rearwin

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