	US 7,590,209 B2
	Method and computer program for identifying a transition in a phase-shift keying or frequency-shift keying signal
Stephen Ha, Greenville, Tex. (US)
Assigned to L3 Communications Integrated Systems L.P., Greenville, Tex. (US)
Filed on Dec. 30, 2005, as Appl. No. 11/323,835.
Prior Publication US 2007/0153947 A1, Jul. 05, 2007
Int. Cl. H04L 7/00 (2006.01)

U.S. Cl. 375—355

14 Claims

1. A system for identifying at least one phase transition in a phase-shift keying signal comprising a plurality of data samples corresponding to phase values, the system comprising:

a memory operable to store computing device executable instructions; and

a computing device operable to

select a portion of the signal to analyze;

apply a transform to the signal to obtain a frequency spectrum;

determine a maximum frequency spectrum corresponding to a first carrier frequency;

determine a starting approximation value of a slope of the phase transition;

calculate a bounded limit of slopes within which to search for the phase transition;

select a plurality of lines, each having a slope within the bounded limit and an initial value, wherein each line passes through at least one of the data samples;

calculate a sum for the data samples associated with each of the lines;

based on the sum for the data samples, identify a line that corresponds to a location of the phase transition;

determine a second carrier frequency corresponding to a second non-transition portion after the phase transition; and

calculate a magnitude of a change in phase by determining a vertical distance of the phase transition lying between the first carrier frequency, which corresponds to a first non-transition portion before the phase transition, and the second carrier frequency.