Patent ID: 6044071
Filing Date: 2000-03-28
Classification: G01S

Abstract:
A system for providing a signal structure for code-division multiplexed radio positioning comprising:means for providing an available radio frequency band for signal transmission,a coherent signal source from which carrier frequency and all lower frequencies used in code definition are derived through frequency synthesis,means for providing a radio frequency carrier approximately centered in the available band,means providing binary phase shift modulation of said carrier frequency by a composite signal made up of:(a) a first coded signal whose code is publicly known having a short repeat interval, whose spectral content lies within the center portion of said available band and(b) a second coded signal having a much longer repeat-interval composed of repetitions of said multi-bit symbol repeated in direct or inverted form according to the values of said second coded signal, not publicly released, whose repeat interval is much longer than that of said first coded signal,wherein said multi-bit symbol has an odd number of chips with equal numbers of binary 0 and 1 bit values, and is chosen from among all such multi-bit signals for its having low autocorrelation values with shifted versions of itself.