Multipath compensation for code phase signals

• US 5,493,588 A
• Filed: 12/09/1994
• Issued: 02/20/1996
• Est. Priority Date: 01/22/1992
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Lennen, Gary R.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Bocure, Tesfaldet
• Application Number:
  US08/353,498
• Time in Patent Office: 438 Days
• Field of Search: 375/355, 375/365, 375/366, 375/367, 375/368, 375/347, 375/267, 375/285, 375/208, 342/350, 342/356, 342/357, 342/358, 342/378, 364/728.03
• US Class Current: 375/343
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/709 Correlator structure

Abstract

Methods for synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, which consists of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal. An idealized correlation function A_I (t), formed from the product of a digital reference signal with a time-shifted reference signal, and a measured correlation signal A_M (t), formed from the product of a received signal and a time-shifted reference signal, are computed. Peak amplitudes A_M (p_M) and A_I (p_I) are found for the respective measurable and idealized punctual code phase shifts p_M and p_I. In a first embodiment of the invention, the correlation measurements formed on the early side (or on the late side) of the peak for the correlation function A(t) are combined to form an estimate of the time delay associated with a multipath signal. In a second embodiment, correlation measurements formed on both the early and late sides of the peak are combined to form an estimate of the multipath time delay. In a third embodiment, a gradient difference is formed from two sets of correlation measurements to estimate the multipath time delay. In a fourth embodiment, correlation functions formed from in-phase and quadrature signals are used to estimate the multipath time delay. This fourth embodiment allows code phase multipath time delay to be measured in the absence of receiver carrier phase lock. All four embodiments may be used in a fixed amplitude variable time (FAVT) mode and in a fixed time variable amplitude (FTVA) mode.

Claims

1. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite code phase SATPS signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of U early code phase shift values e_I,i <

p_I (i=1, . . . , U;

U≧

2) for the first correlation function A_I (t) for which the code phase shift differences p_I -e_I,i =Δ

_I,e,i have selected values;

(6) determining a sequence of U early code phase shift values e_M,i <

p_M (i=1, . . . , U) for the second correlation function A_M (t) for which the code phase shift differences p_M -e_M,i =Δ

_M,e,i have selected values;

(7) forming a sequence of U correlation amplitude ratios defined by the relations x_e,i =(A_M (e_M,i)/A_M (p_M))-(A_I (e_I,i)/A_I (p_I)) for i=1, . . . , U;

(8) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =F.sub.e (x.sub.e,1, x.sub.e,2, . . . , x.sub.e,U),

where F_e is a selected function of U variables; and

(9) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

2. The method of claim 1, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

3. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of V late code phase shift values l_I,j >

p_I (j =1, . . . , V;

V≧

2) for the first correlation function A_I (t) for which the code phase shift differences p_I -l_I,j =Δ

_I,l,j have selected values;

(6) determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t) for which the code phase shift differences p_M -l_M,j =Δ

_M,l,j have selected values;

(7) forming a sequence of V correlation amplitude ratios defined by the relations x_l,i =(A_M (l_M,j)/A_M (p_M))-(A_I (l_I,j)/A_I (p_I)) for j=1, . . . , V;

(8) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =F.sub.l (x.sub.l,1,x.sub.l,2, . . . , x.sub.l,V),

where F_l is a selected function of V variables; and

(9) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

4. The method of claim 3, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

5. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of U early code phase shift values e_I,i <

p_I (i=1, . . . , U;

U≧

1) for the first correlation function A_I (t) for which the code phase shift differences p_I -e_I,i =Δ

_I,e,i have selected values;

(6) determining a sequence of U early code phase shift values e_M,i <

p_M (i=1, . . . , U) for the second correlation function A_M (t) for which the code phase shift differences p_M -e_M,i =Δ

_M,e,i have selected values;

(7) determining a sequence of V late code phase shift values l_I,j >

p_I (j =1, . . . , V;

U+V≧

2) for the first correlation function A_I (t) for which the code phase shift differences p_I -l_I,j =Δ

_I,l,j have selected values;

(8) determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t) for which the code phase shift differences p_M -l_M,j =Δ

_M,l,j have selected values;

(9) forming a sequence of L correlation amplitude ratios defined by the relations x_e,i =(A_M (e_M,i)/A_M (p_M)) -(A_I (e_I,i)/A_I (p_I)) for i=1, . . . , U;

(10) forming a sequence Of V correlation amplitude ratios defined by the relations x_l,j =(A_M (l_M,j)/A_M (p_M)) -(A_I (l_I,j)/A_I (p_I)) for j=1, . . . , V;

(11 ) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =F(x.sub.e,1, . . . , x.sub.e,U, x.sub.l,1, . . . , x.sub.l,V),

where F is a selected function of U+V variables; and

(12) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

6. The method of claim 5, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component. S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

7. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of U early code phase shift values e_I,i <

p_I (i=1, . . . , U;

U≧

2) for the first correlation function A_I (t) for which the code phase shift amplitude ratios A_I (e_I,i)/A_I (p_I)=r_I,e,i have selected values;

(6) determining a sequence of U early code phase shift values e_M,i <

p_M (i=1, . . . , U) for the second correlation function A_M (t) for which the code phase shift amplitude ratios A_M (e_M,i)/A_M (p_M)=r_M,e,i have selected values;

(7) forming a sequence of U code phase shift differences defined by the relations Y_e,i =(p_M -e_M,i)-(p_I -e_I,i) for i=1, . . . , U;

(8) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =G.sub.e (y.sub.e,1, y.sub.e,2, . . . , y.sub.e,U),

where G_e is a selected function of U variables; and

(9) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

8. The method of claim 7, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship-between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

9. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of V late code phase shift values l_I,j >

p_I (j =1, . . . , V;

V≧

2) for the first correlation function A_I (t) for which the code phase shift amplitude ratios A_I (l_I,j)/A_I (p_I)=r_I,e,j have selected values;

(6) determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t) for which the code phase shift amplitude ratios A_M (l_M,j)/A_M (p_M)=r_M,l,j have selected values;

(7) forming a sequence of V code phase shift differences defined by the relations y_l,j =(p_M -l_M,j)-(p_I -l_I,j) for j=1, . . . , V;

(8) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =G.sub.l (y.sub.l,1, y.sub.l,2, . . . , y.sub.l,V),

where G_l is a selected function of V variables; and

(9) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

10. The method of claim 9, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship-between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

11. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of U early code phase shift values e_I,i <

p_I (i=1, . . . , U;

U≧

1) for the first correlation function A_I (t) for which the code phase shift amplitude ratios A_I (e_I,i)/A_I (p_I)=r_I,e,i have selected values;

(6) determining a sequence of U early code phase shift values e_M,i <

p_M (i=1, . . . , U) for the second correlation function A_M (t) for which the code phase shift amplitude ratios A_M (e_M,i)/A_M (p_M)=r_M,e,i have selected values;

(7) determining a sequence of V late code phase shift values l_I,j >

p_I (j =1, . . . , V;

U+V≧

2) for the first correlation function A_I (t) for which the code phase shift amplitude ratios A_I (l_I,j)/A_I (p_I)=r_I,e,j have selected values;

(8) determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t) for which the code phase shift amplitude ratios A_M (l_M,j)/A_M (p_M)=r_M,l,j have selected values;

(9) forming a sequence of U code phase shift differences defined by the relations y_e,i =(p_M -e_M,i)-(p_I -e_I,i) for i=1, . . . , U;

(10) forming a sequence Of V code phase shift differences defined by the relations y_l,j =(p_M -l_M,j)-(p_I -l_I,j) for j=1, . . . , V;

(11) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =G(y.sub.e,1, . . . , y.sub.e,U, y.sub.l,1, . . . , y.sub.l,V),

where G is a selected function of U+V variables; and

(12) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

12. The method of claim 11, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship-between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

13. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of U early code phase shift values e_I,j <

p_I (i=1, . . . , U;

U≧

1) for the first correlation function A_I (t) for which the code phase shift differences p_I -e_I,i =Δ

_I,e,i have selected values, and forming a first sequence of gradient values B_I,e,i =(A_I (p_I)-A_I (e_I,i))/(p_I -e_I,i);

(6) determining a sequence of U early code phase shift values e_M,i <

p_M (i=1, . . . , U) for the second correlation function A_M (t), for which the code phase shift differences p_M -e_M,i =Δ

_M,e,i have selected values, and forming a second sequence of gradient values B_M,e,i =(A_M (p_M)-A_M (e_M,i))/(p_M -e_M,i);

(7) forming a sequence of U gradient differences z_e,i =B_M,e,i -B_I,e,i for i=1, . . . , U;

(8) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =H.sub.e (z.sub.e,1, . . . , z.sub.e,U),

where H_e is a selected function of U variables; and

(9) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

14. The method of claim 13, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship-between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

15. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of V late code phase shift values l_I,j >

p_I (j =1, . . . , V;

V≧

1) for the first correlation function A_I (t) for which the code phase shift differences p_I -l_I,j =Δ

_I,l,j have selected values, and forming a first sequence of gradient values B_I,l,j =(A_I (p_I)-A_I (l_I,j))/(p_I -l_I,j);

(6) determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t), for which the code phase shift differences p_M -l_M,j =Δ

_M,l,j have selected values, and forming a second sequence of gradient values B_M,l,j =(A_M (p_M)-A_M (l_M,j))/(p_M -l_M,j);

(7) forming a sequence of V gradient differences z_l,j =B_M,l,j -B_I,l,j for j=1, . . . , V;

(8) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =H.sub.l (z.sub.l,1, . . . , z.sub.l,V),

where H_l is a selected function of V variables; and

(9) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

16. The method of claim 15, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship-between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

22. The method of claim 15, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship-between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

17. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of U early code phase shift values e_I,i <

p_I (i=1, . . . , U;

U≧

1) for the first correlation function A_I (t) for which the code phase shift differences p_I -e_I,i =Δ

_I,e,i have selected values, and forming a first sequence of gradient values B_I,e,i =(A_I (p_I)-A_I (e_I,i))/(p_I -e_I,i);

(6) determining a sequence of U early code phase shift values e_M,i <

p_M (i=1, . . . , U) for the second correlation function A_M (t) for which the code phase shift differences p_M -e_M,i =Δ

_M,e,i have selected values, and forming a second sequence of gradient values B_M,e,i =(A_M (p_M)-A_M (e_M,i))/(p_M -e_M,i);

(7) determining a sequence of V late code phase shift values l_I,j >

p_I (j =1, . . . , V;

U+V≧

2) for the first correlation function A_I (t) for which the code phase shift p_I -e_I,j =Δ

_I,e,j have selected values and forming a first sequence of gradient values B_I,l,j =(A_I (p_I)-A_I (l_I,j))/(p_I -l_I,j);

(8) determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t) for which the code phase shift differences p_M -l_M,j =Δ

_M,l,j have selected values, and forming a second sequence of gradient values B_M,l,j =(A_M (p_M)-A_M (l_M,j))/(p_M -l_M,j);

(9) forming a sequence of U gradient differences z_e,i =B_M,e,i -B_I,e,i for i=1, . . . , U;

(10) forming a sequence of V gradient differences z_e,j =B_M,e,j -B_I,e,j for j=1, . . . , V;

(11) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =H(z.sub.e,1, . . . , z.sub.e,U, z.sub.l,1, . . . , z.sub.l,V),

where H is a selected function of U+V variables; and

(12) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

18. The method of claim 17, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship-between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

24. The method of claim 17, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship-between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

19. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of U early code phase shift values e_I,i <

p_I (i=1, . . . , U;

U≧

1) for the first correlation function A_I (t) for which the correlation amplitude ratios r_I,e,i =A_I (e_I,i)/A_I (p_I) have selected values, and forming a first sequence of gradient values B_I,e,i =(A_I (p_I)-A_I (e_I,i))/(p_I -e_I,i);

(6) determining a sequence of U early code phase shift values e_M,i <

p_M (i=1, . . . , U) for the second correlation function A_M (t), for which the correlation amplitude ratios r_M,e,i =A_M (e_M,i)/A_M (p_M) have selected values, and forming a second sequence of gradient values B_M,e,i =(A_M (p_M) -A_M (e_M,i))/(p_M -e_M,i);

(7) forming a sequence of U gradient differences z_e,i =B_M,e,i -B_I,e,i for i=1, . . . , U;

(8) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =K.sub.e (z.sub.e,1, . . . , z.sub.e,U),

where K_e is a selected function of U variables; and

(9) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

20. The method of claim 19, wherein the steps (1), (2) and (3) comprise the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship-between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function.

21. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=P_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of V late code phase shift values l_i,j >

p_I (j =1, . . . , V;

V≧

1) for the first correlation function A_I (t.sub.), for which the correlation amplitude ratios r_I,l,j =A_I (l_I,j)/A_I (p_I) have selected values, and forming a sequence of gradient values B_I,l,j =(A_I (p_I)-A_I (l_I,j))/(p_I -l_I,j);

(6) determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t), for which the correlation amplitude ratios r_M,l,j =A_M (l_M,l)/A_M (p_M) have selected values, and forming a sequence of gradient values B_M,l,j =(A_M (p_M)-A_M (l_M,j))/(p_M -l_M,j);

(7) forming a sequence of V gradient differences z_l,j =B_M,l,j -B_I,l,j for j=1, . . . ,V;

(8) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =K.sub.l (z.sub.l,1, . . . , z.sub.l,V),

where K_l is a selected function of V variables; and

(9) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

23. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

(1) generating a first correlation function A_I (t) representing a timing relationship between a selected reference signal and the reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

(2) receiving a distorted composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal;

(3) generating a second correlation function A_M (t) representing a timing relationship between the composite signal and the reference signal;

(4) determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the second correlation function;

(5) determining a sequence of U early code phase shift values e_I,i <

p_I (i=1, . . . , U;

U≧

1) for the first correlation function A_I (t) for which the correlation amplitude ratios r_I,e,i =A_I (e_I,i)/A_I (p_I) have selected values, and forming a first sequence of gradient values B_I,e,i =(A_I (p_I)-A_I (e_I,i))/(p_I -e_I,i);

(6) determining a sequence of U early code phase shift values e_M,i <

p_M (i=1, . . . , U) for the second correlation function A_M (t) for which the correlation amplitude ratios r_M,e,i =A_M (e_M,i)/A_M (p_M) have selected values, and forming a second sequence of gradient values B_M,e,i =(A_M (p_M) -A_M (e_M,i))/(p_M -e_M,i);

(7) determining a sequence of V late code phase shift values l_I,j >

p_I (j =1, . . . , V;

U+V≧

1) for the first correlation function A_I (t) for which the correlation amplitude ratios r_I,l,j =A_I (l_I,j)/A_I (p_I) have selected values and forming a sequence of gradient values B_I,l,j =(A_I (p_I)-A_I (l_I,j))/(p_I -l_I,j);

(8) determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t) for which the correlation amplitude ratios r_M,l,j =A_M (l_M,l)/A_M (p_M) have selected values, and forming a sequence of gradient values B_M,l,j =(A_M (p_M)-A_M (l_M,j))/(p_M -l_M,j);

(9) forming a sequence of U gradient differences z_e,i =B_M,e,i -B_I,e,i for i=1, . . . , U;

(10) forming a sequence of V gradient differences z_l,j =B_M,l,j -B_I,l,j for j=1, . . . , V;

(11) determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =K(z.sub.e,1, . . . , z.sub.e,U, z.sub.l,1, . . . , z.sub.l,V),

where K is a selected function of U+V variables; and

(12) subtracting the difference p_M -p_I from an apparent time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

25. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function;

determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the first combined correlation function;

determining a sequence of U early code phase shift values e_I,i <

p_I (i=1, . . . , U;

U≧

1) for the first correlation function A_I (t) for which the code phase shift differences p_I -e_I,i =Δ

_I,e,i have selected values;

determining a sequence of U early code phase shift values e_M,i <

p_M (i =1, . . . , U) for the second correlation function A_M (t) for which the code phase shift differences p_M -e_M,i =Δ

_M,e,i have selected values;

forming a sequence of U correlation amplitude ratios defined by the relations x_e,i =(A_M (e_M,i)/A_M (p_M))-(A_I (e_I,i)/A_I (p_I)) for i=1, . . . , U; and

determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =F.sub.e (x.sub.e,1, x.sub.e,2, . . . , x.sub.e,U),

where F_e is a selected function of U variables.

26. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function;

determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the first combined correlation function;

determining a sequence of V late code phase shift values l_I,j >

p_I (j=1, . . . , V;

V≧

1) for the first correlation function A_I (t) for which the code phase shift differences p_I -l_I,j =Δ

_I,l,j have selected values;

determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t) for which the code phase shift differences p_M -l_M,i =Δ

_M,l,j have selected values;

forming a sequence of V correlation amplitude ratios defined by the relations x_l,i =(A_M (l_M,j)/A_M (p_M))-(A_I (l_I,j)/A_I (p_I)) for j=1, . . . , V;

determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =F.sub.l (x.sub.l,1, x.sub.l,2, . . . , x.sub.l,V),

where F_l is a selected function of V variables; and

subtracting the difference p_M -p_I from an apparent, time of arrival of the composite code phase SATPS signal to redetermine the time of arrival of this signal.

27. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function;

determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the first combined correlation function;

determining a sequence of U early code phase shift values e_I,i <

p_I (i=1, . . . , U;

U≧

1) for the first correlation function A_I (t) for which the code phase shift amplitude ratios A_I (e_I,i)/A_I (p_I)=r_I,e,i have selected values;

determining a sequence of U early code phase shift values e_M,i <

p_M (i =1, . . . , U) for the second correlation function A_M (t) for which the code phase shift amplitude ratios A_M (e_M,i)/A_M (p_M)=r_M,e,i have selected values;

forming a sequence of U code phase shift differences defined by the relations y_e,i =(p_M -e_M,i)-(p_I -e_I,i) for i=1, . . . , U; and

determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =G.sub.e (y.sub.e,1, y.sub.e,2, . . . , y.sub.e,U),

where G_e is a selected function of U variables.

28. A method of synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, the composite signal consisting of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal, the method comprising the steps of:

receiving a selected reference signal S_ref (t) and generating an in-phase reference signal component S_ref,in-phase (t) and a quadrature reference signal component S_ref,quad (t) from this reference signal, where the reference signal is a digital signal with a timing cycle of selected length, and where A_I (t) has a peak amplitude at an unknown code phase shift value t=p_I ;

receiving a composite signal S_comp (t), consisting of a preferred, interference-free signal distorted by at least one interfering signal, and generating an in-phase reference signal component S_comp,in-phase (t) and a quadrature reference signal component S_comp,quad (t) from this composite signal;

generating a first correlation function A_I,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a second correlation function A_M,in-phase (t) representing a timing relationship between the signal S_ref,in-phase (t) and the signal S_comp,in-phase (t);

generating a third correlation function A_I,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a fourth correlation function A_M,quad (t) representing a timing relationship between the signal S_ref,quad (t) and the signal S_comp,quad (t);

generating a first combined correlation function

space="preserve" listing-type="equation">A.sub.I (t)=[(A.sub.I,in-phase (t)).sup.2 +(A.sub.I,quad (t)).sup.2 ].sup.1/2 ;

generating a second combined correlation function

space="preserve" listing-type="equation">A.sub.M (t)=[(A.sub.M,in-phase (t)).sup.2 +(A.sub.M,quad (t)).sup.2 ].sup.1/2 ; and

determining a nominal peak amplitude A_I (p_I) and the corresponding code phase shift value t=p_I of the first combined correlation function;

determining a nominal peak amplitude A_M (p_M) and the corresponding code phase shift value t=p_M of the first combined correlation function;

determining a sequence of V late code phase shift values l_I,j >

p_I (j=1, . . . , V;

V≧

1) for the first correlation function A_I (t) for which the code phase shift amplitude ratios A_I (l_I,j)/A_I (p_I)=r_I,e,j have selected values;

determining a sequence of V late code phase shift values l_M,j >

p_M (j=1, . . . , V) for the second correlation function A_M (t) for which the code phase shift amplitude ratios A_M (l_M,j)/A_M (p_M)=r_M,l,j have selected values;

forming a sequence of V code phase shift differences defined by the relations y_l,j =(p_M -l_M,j)-(p_I -l_I,j) for j=1, . . . , V; and

determining the difference in punctual code phase shift between the first and second correlation functions by the relation

space="preserve" listing-type="equation">p.sub.M -p.sub.I =G.sub.l (y.sub.l,1, y.sub.l,2, . . . , y.sub.l,V),

where G_l is a selected function of V variables.