Patent ID: 6370207
Filing Date: 2002-04-09
Classification: G01S,H04B

Abstract:
A process for optimally estimating the direct path propagation delay of a received signal when also receiving one or more secondary propagation path signals, the process comprising the steps:A. selecting a direct propagation path signal delay estimate {circumflex over (&tgr;)} and a secondary path additional propagation delay estimate &Dgr;{circumflex over (&tgr;)} as a point ({circumflex over (&tgr;)}, &Dgr;{circumflex over (&tgr;)}) on a two-dimensional plane; B. computing the value of the cross-correlation R&af;(Ï„^)=&Integral;t0t0+T&it;r~&af;(t)&it;m&af;(t-Ï„^)&it;&dd;t,â€ƒwhere {tilde over (r)}(t) represents the received signal translated to baseband, m(tâˆ’{circumflex over (&tgr;)}) represents a replica of the signal modulation delayed by {circumflex over (&tgr;)}, and [t0,t0+T] is the interval of observation of {tilde over (r)}(t); C. computing the value of the cross-correlation R&af;(Ï„^+Î”Ï„^)=&Integral;t0t0+T&it;r~&af;(t)&it;m&af;(t-(Ï„^+Î”Ï„^))&it;&dd;t,â€ƒwhere m(tâˆ’({circumflex over (&tgr;)}+&Dgr;{circumflex over (&tgr;)})) represents a replica of the signal modulation delayed by {circumflex over (&tgr;)}+&Dgr;{circumflex over (&tgr;)}, and {tilde over (r)}(t) and [t0,t0+T] are as defined in step B; D. Obtaining the value of the zero-delay signal modulation replica autocorrelation K&af;(0)=&Integral;t0t0+T&it;m2&af;(t)&it;&dd;t,â€ƒand the value of the signal modulation replica autocorrelation K&af;(Î”Ï„^)=&Integral;t0t0+T&it;m&af;(t)&it;m&af;(t-Î”Ï„^)&it;&dd;tâ€ƒat the delay &Dgr;{circumflex over (&tgr;)}; E. computing a=(K&af;(0)-Î³i)&it;Re&af;[R&af;(Ï„^)]-Re&af;[R&af;(Ï„^+Î”Ï„^)&it;K&af;(Î”Ï„^)](K&af;(0)+Î³i&it;Î±c2)&it;(K&af;(0)-Î³i)-K2&af;(Î”Ï„^),&NewLine;&it;b=(K&af;(0)+Î±c2&it;Î³i)&it;Re&af;[R&af;(Ï„^+Î”Ï„^)]-Re&af;[R&af;(Ï„^)&it;K&af;(Î”Ï„^)](K&af;(0)+Î³i&it;Î±c2)&it;(K&af;(0)-Î³i)-K2&af;(Î”Ï„^),&NewLine;&it;c=(K&af;(0)-Î³i)&it;Im&af;[R&af;(Ï„^)]-Im&af;[R&af;(Ï„^+Î”Ï„)&it;K&af;(Î”Ï„^)](K&af;(0)+Î³i&it;Î±c2)&it;(K&af;(0)-Î³i)-K2&af;(Î”Ï„^),&NewLine;&it;d=(K&af;(0)+Î±c2&it;Î³i)&it;Im&af;[R&af;(Ï„^+Î”Ï„^)]-Im&af;[R&af;(Ï„^)&it;K&af;(Î”Ï„^)](K&af;(0)+Î³i&it;Î±c2)&it;(K&af;(0)-Î³i)-K2&af;(Î”Ï„^),â€ƒusing the values obtained in steps B, C and D, where Re stands for the real part and Im stands for the imaginary part, with &ggr;i=0 and with &agr;c a maximum value selected for the secondary path signal relative amplitude; F. computing an estimation statistic &Lgr;=2Re[(aâˆ’jc)R({circumflex over (&tgr;)})]+2Re[(bâˆ’jd)R({circumflex over (&tgr;)}+&Dgr;{circumflex over (&tgr;)})]âˆ’2(ab+cd)K(&Dgr;{circumflex over (&tgr;)})âˆ’(a2+b2+c2+d2)K(0) â€ƒwith the values a, b, c, and d obtained from step E; G. assigning the computed estimation statistic A of step F to the point ({circumflex over (&tgr;)},&Dgr;{circumflex over (&tgr;)}) of step A.