Variable suppression of multipath signal effects
First Claim
1. A method of formation of an autocorrelation difference function of an incoming signal that reduces effects of presence of a multipath signal in the incoming signal, the method comprising the steps of:
- (1) receiving an incoming digital signal s(t) that can vary with the time t and that has a digital signal bit period with a selected length Δ
τ
chip ;
(2) forming a first signal product difference
space="preserve" listing-type="equation">Δ
s.sub.1 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1(t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1(t+τ
-t.sub.L ;
qL),where Sd (t) is a selected reference signal, w1(t;
q) is a first selected, non-constant weighting signal that may depend upon one or more parameters q, τ
is a selected time shift, tE and tL are first and second selected time values satisfying 0<
tL -tE <
2Δ
τ
chip ;
(3) forming a second signal product difference
space="preserve" listing-type="equation">Δ
s.sub.2 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1 (t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1 (t+τ
-t.sub.L ;
qL),where w1 (t;
q) is a second selected weighting signal that may depend upon one or more parameters q;
(4) selecting an integer n≧
2 and setting an accumulation An-1 =0;
(5) examining the incoming digital signal bit value bn, for the time interval defined by nΔ
τ
chip ≦
t<
(n+1)Δ
τ
chip, and the immediately preceding digital bit value bn-1 of the reference signal Sd (t);
(6) when bn-1 ≠
bn, computing the contribution of the first signal product difference over a time interval In ={t'"'"'|tn-1 +Δ
<
t'"'"'≦
tn +Δ
}, where Δ
is a selected time value satisfying 0≦
Δ
<
Δ
τ
chip, to an autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this contribution to An-1 to form An ;
(7) when bn-1 =bn, computing the contribution of the second signal product difference over the time interval In to the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this integral or sum to An-1 to form An ;
(8) replacing the integer n by the integer n+1 and repeating steps (5), (6) and (7) at least once;
(9) interpreting the accumulation AN for a selected positive integer N as the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t);
(10) determining at least one value t0 of the time shift variable τ
for which the autocorretation difference function Δ
AC#(τ
;
q) changes sign; and
(11) interpreting the time value t=t0 as an estimate of the time at which a signal, which is substantially free of the presence of a multipath signal, was received.
2 Assignments
0 Petitions
Accused Products
Abstract
Method and apparatus for formation of an autocorrelation difference function of an incoming digital signal that reduces the effects of presence of a multipath signal or of noise in an incoming digital composite signal. An incoming digital composite signal, including direct and multipath signals, is received that has a bit value transition interval of length Δτchip. Two or three consecutive bit values bn-2, bn-1 and bn of the direct (ideal) signal are examined. If a test condition for these bit values is satisfied, a first non-uniform weighting function w1(t) is used to compute the contribution of a time interval In ={t'"'"'|tn-1 +Δ<t'"'"'≦tn +Δ}, where Δ is a selected time value satisfying 0≦Δ<Δτchip, to first and second autocorrelation functions AC#(τ;E) and AC#(τ;L) with respective selected first and second time shifts τ=tE and τ=tL (>tE) If the test condition is not satisfied, a second weighting function w1 (t) is used to compute the contribution of the time interval In to AC#(τ;E) and AC#(τ;L). An autocorrelation difference function ΔAC#(τ)=AC#(τ;E) and AC#(τ;L) is formed in which the effects of noise or of multipath signals is suppressed, relative these effects in a conventionally computed autocorrelation difference function ΔAC(τ)=AC(τ;E)-AC(τ;L).
-
Citations
18 Claims
-
1. A method of formation of an autocorrelation difference function of an incoming signal that reduces effects of presence of a multipath signal in the incoming signal, the method comprising the steps of:
-
(1) receiving an incoming digital signal s(t) that can vary with the time t and that has a digital signal bit period with a selected length Δ
τ
chip ;(2) forming a first signal product difference
space="preserve" listing-type="equation">Δ
s.sub.1 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1(t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1(t+τ
-t.sub.L ;
qL),where Sd (t) is a selected reference signal, w1(t;
q) is a first selected, non-constant weighting signal that may depend upon one or more parameters q, τ
is a selected time shift, tE and tL are first and second selected time values satisfying 0<
tL -tE <
2Δ
τ
chip ;(3) forming a second signal product difference
space="preserve" listing-type="equation">Δ
s.sub.2 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1 (t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1 (t+τ
-t.sub.L ;
qL),where w1 (t;
q) is a second selected weighting signal that may depend upon one or more parameters q;(4) selecting an integer n≧
2 and setting an accumulation An-1 =0;(5) examining the incoming digital signal bit value bn, for the time interval defined by nΔ
τ
chip ≦
t<
(n+1)Δ
τ
chip, and the immediately preceding digital bit value bn-1 of the reference signal Sd (t);(6) when bn-1 ≠
bn, computing the contribution of the first signal product difference over a time interval In ={t'"'"'|tn-1 +Δ
<
t'"'"'≦
tn +Δ
}, where Δ
is a selected time value satisfying 0≦
Δ
<
Δ
τ
chip, to an autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this contribution to An-1 to form An ;(7) when bn-1 =bn, computing the contribution of the second signal product difference over the time interval In to the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this integral or sum to An-1 to form An ;(8) replacing the integer n by the integer n+1 and repeating steps (5), (6) and (7) at least once; (9) interpreting the accumulation AN for a selected positive integer N as the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t);(10) determining at least one value t0 of the time shift variable τ
for which the autocorretation difference function Δ
AC#(τ
;
q) changes sign; and(11) interpreting the time value t=t0 as an estimate of the time at which a signal, which is substantially free of the presence of a multipath signal, was received. - View Dependent Claims (2, 3, 4)
-
-
5. A method of formation of an autocorrelation difference function of an incoming signal that reduces effects of presence of a multipath signal in the incoming signal, the method comprising the steps of:
-
(1) receiving an incoming digital signal s(t) that can vary with the time t and that has a digital signal bit period with a selected length Δ
τ
chip ;(2) forming a first signal product difference
space="preserve" listing-type="equation">Δ
s.sub.1 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1(t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (tτ
-t.sub.L)w1(t+τ
-t.sub.L ;
qL),where Sd (t) is a selected reference signal, w1(t;
q) is a first selected, non-constant weighting signal that may depend upon one or more parameters q, τ
is a selected time shift, tE and tL are first and second selected time values satisfying 0<
tL -tE <
2Δ
τ
chip ;(3) forming a second signal product difference
space="preserve" listing-type="equation">Δ
s.sub.2 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1 (t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1 (t+τ
-t.sub.L ;
qL),where w1 (t;
q) is a second selected weighting signal that may depend upon one or more parameters q;(4) selecting an integer n≧
3 and setting an accumulation An-1 =0;(5) examining the incoming digital signal bit value bn, for the time interval defined by nΔ
τ
chip ≦
t<
(n+1)Δ
τ
chip, and the two immediately preceding digital bit values bn-1 and bn-2 of the reference signal Sd (t);(6) when bn-2 =bn-1 and bn-1 ≠
bn, computing the contribution of the first signal product difference over a time interval In ={t'"'"'|tn-1 +Δ
<
t'"'"' ≦
tn +Δ
}, where Δ
is a selected time value satisfying 0≦
Δ
<
Δ
τ
chip, to an autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this contribution to An-1 to form An ;(7) when bn-2 ≠
bn-1 or bn-1 =bn, computing the contribution of the second signal product difference over the time interval In to the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this integral or sum to An-1 to form An ;(8) replacing the integer n by the integer n+1 and repeating steps (5), (6) and (7) at least once; (9) interpreting the accumulation AN for a selected positive integer N as the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t); and(10) determining at least one value t0 of the time shift variable τ
for which the autocorrelation difference function Δ
AC#(τ
;
q) changes sign; and(11) interpreting the time value t=t0 as an estimate of the time at which a signal, which is substantially free of the presence of a multipath signal, was received. - View Dependent Claims (6, 7, 8)
-
-
9. Apparatus for formation of an autocorrelation difference function of an incoming signal that reduces effects of presence of a multipath signal in the incoming signal, the apparatus comprising:
-
a signal antenna that receives an incoming digital signal s(t) that can vary with the time t and that has a digital signal bit period with a selected length Δ
τ
chip ;a signal receiver/processor, including a computer, that generates a selected digital reference signal Sd (t), that examines a signal bit value bn and the immediately preceding digital bit value bn-1 of the reference signal Sd (t), and that is programmed to; (1) receive an incoming digital signal s(t) that can vary with the time t and that has a digital signal bit period with a selected length Δ
tchip ;(2) form a first signal product difference
space="preserve" listing-type="equation">Δ
s.sub.1 (t;
τ
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1(t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1(t+τ
-t.sub.L ;
qL),where w1(t;
q) is a first selected, non-constant weighting signal that may depend upon one or more parameters q, τ
is a selected time shift, tE and tL are first and second selected time values satisfying 0<
tL -tE <
2Δ
τ
chip ;(3) form a second signal product difference
space="preserve" listing-type="equation">Δ
s.sub.2 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1 (t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1 (t+τ
-t.sub.L ;
qL),where w1 (t;
q) is a second selected weighting signal that may depend upon one or more parameters q;(4) select an integer n≧
2 and set an accumulation An-1 =0;(5) examine the bit value bn, for a time interval defined by nΔ
τ
chip ≦
t<
(n+1)Δ
τ
chip, and the immediately preceding bit value bn-1 of the reference signal Sd (t);(6) when bn-1 ≠
bn, compute the contribution of the first signal product difference over the time interval In ={t'"'"'|tn-1 +Δ
<
t'"'"'≦
tn +Δ
}, where Δ
is a selected time value satisfying 0≦
Δ
<
Δ
τ
chip to an autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this contribution to An-1 to form An ;(7) when bn-1 =bn, compute the contribution of the second signal product difference over the time interval In to the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this integral or sum to An-1 to form An ;(8) replace the integer n by the integer n+1 and repeat steps (5), (6) and (7) at least once; (9) interpret the accumulation AN for a selected positive integer N as the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t);(10) determine at least one value t0 of the time shift variable τ
for which the autocorrelation difference function Δ
AC#(τ
;
q) changes sign; and(11) interpret the time value t=t0 as an estimate of the time at which a signal, which is substantially free of the presence of a multipath signal, was received. - View Dependent Claims (10, 11, 12)
-
-
13. Apparatus for formation of an autocorrelation difference function of an incoming signal that reduces effects of presence of a multipath signal in the incoming signal, the apparatus comprising:
-
a signal antenna that receives an incoming digital signal s(t) that can vary with the time t and that has a digital signal bit period with a selected length Δ
tchip ;a signal receiver/processor, including a computer, that generates a selected digital reference signal Sd (t), that examines a bit value bn and the two immediately preceding digital bit values bn-1 and bn-2 of the reference signal Sd (t), and that is programmed to; (1) receive an incoming digital signal s(t) that can vary with the time t and that has a digital signal bit period with a selected length Δ
τ
chip ;(2) form a first signal product difference
space="preserve" listing-type="equation">Δ
s.sub.1 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1(t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1(t+τ
-t.sub.L ;
qL),where w1(t;
q) is a first selected, non-constant weighting signal that may depend upon one or more parameters q, τ
is a selected time shift, tE and tL are first and second selected time values satisfying 0<
tL -tE <
2Δ
τ
chip ;(3) form a second signal product difference
space="preserve" listing-type="equation">Δ
s.sub.2 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1 (t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1 (t+τ
-t.sub.L ;
qL),where w1'"'"'(t;
q) is a second selected weighting signal that may depend upon one or more parameters q;(4) select an integer n≧
3 and set an accumulation An-1 =0;(5) examine the bit value bn, for the time interval defined by nΔ
τ
chip ≦
t≦
(n+1)Δ
τ
chip, and the two immediately preceding digital bit values bn-1 and bn-2 of the reference signal Sd (t);(6) when bn-2 =bn-1 and bn-1 ≠
bn, compute the contribution of the first signal product difference over a time interval In ={t'"'"'|tn-1 +Δ
<
T'"'"'≦
tn +Δ
}, where Δ
is a selected time value satisfying 0≦
Δ
<
Δ
τ
chip, to an autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this contribution to An-1 to form An ;(7) when bn-2 ≠
bn-1 or bn-1 =bn, compute the contribution of the second signal product difference over the time interval In to the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this integral or sum to An-1 to form An ;(8) replace the integer n by the integer n+1 and repeat steps (5), (6) and (7) at least once; (9) interpret the accumulation AN for a selected positive integer N as the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t); and(10) determine at least one value t0 of the time shift variable T for which the autocorrelation difference function Δ
AC#(τ
;
q) changes sign; and(11) interpret the time value t=t0 as an estimate of the time at which a signal, which is substantially free of the presence of a multipath signal, was received. - View Dependent Claims (14, 15, 16)
-
-
17. A method of formation of an autocorrelation difference function of an incoming signal that reduces effects of presence of a multipath signal in the incoming signal, the method comprising the steps of:
-
(1) receiving an incoming digital signal s(t) that can vary with the time t and that has a digital signal bit period with a selected length Δ
τ
chip ;(2) forming a first signal product difference
space="preserve" listing-type="equation">Δ
s.sub.1'"'"' (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1(t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1(t+τ
-t.sub.L ;
qL),where Sd (t) is a selected reference signal, w1(t;
q) is a first selected, non-constant weighting signal that may depend upon one or more parameters q and that is periodic with period equal to Δ
τ
chip, τ
is a selected time shift, tE and tL are first and second selected time values satisfying 0<
tL -tE <
2Δ
τ
chip ;(3) forming a second signal product difference
space="preserve" listing-type="equation">Δ
s.sub.2 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1 (t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1 (t+τ
-t.sub.L ;
qL),where w1 (t;
q;
k) is a second selected weighting signal that may depend upon one or more parameters q and that is periodic with period kΔ
τ
chip, where k is a selected integer ≧
2;(4) selecting an integer n≧
2 and setting an accumulation An-1 =0;(5) examining the incoming digital signal bit value bn, for the time interval defined by nΔ
τ
chip ≦
t≦
(n+1)Δ
τ
chip, and the immediately preceding digital bit value bn-1 of the reference signal Sd (t);(6) when bn-1 ≠
bn, computing the contribution of the first signal product difference over a time interval In ={t'"'"'|tn-1 +Δ
<
t'"'"'≦
tn +Δ
}, where Δ
is a selected time value satisfying 0≦
Δ
<
Δ
τ
chip, to an autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this contribution to An-1 to form An ;(7) when bn-1 =bn, computing the contribution of the second signal product difference over the time interval In to an autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this integral or sum to An-1 to form An ;(8) replacing the integer n by the integer n+1 and repeating steps (5), (6) and (7) at least once; (9) interpreting the accumulation AN for a selected positive integer N as an autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t);(10) determining at least one value t0 of the time shift variable τ
for which the autocorrelation difference function Δ
AC#(τ
;
q) changes sign; and(11) interpreting the time value t=t0 as an estimate of the time at which a signal, that is substantially free of the presence of a multipath signal, was received.
-
-
18. A method of formation of an autocorrelation difference function of an incoming signal that reduces effects of presence of a multipath signal in the incoming signal, the method comprising the steps of:
-
(1) receiving an incoming digital signal s(t) that can vary with the time t and that has a digital signal bit period with a selected length Δ
τ
chip ;(2) forming a first signal product difference
space="preserve" listing-type="equation">Δ
s.sub.1 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1(t+τ
-t.sub.E ;
qE)-s(t)S.sub.d (t+τ
-t.sub.L)w1(t+τ
-t.sub.L ;
qL),where Sd (t) is a selected reference signal, w1(t;
q) is a first selected, non-constant weighting signal that may depend upon one or more parameters q and that is periodic with period equal to Δ
τ
chip, τ
is a selected time shift, tE and tL are first and second selected time values satisfying 0<
tL -tE <
2Δ
τ
chip ;(3) forming a second signal product difference
space="preserve" listing-type="equation">Δ
s.sub.2 (t;
τ
;
t.sub.E ;
t.sub.L ;
qE;
qL)=s(t)S.sub.d (t+τ
-t.sub.E)w1 (t+τ
-t.sub.E)-s(t)S.sub.d (t+τ
-t.sub.L)w1 (t+τ
-t.sub.L ;
qL),where w1 (t;
q;
k) is a second selected weighting signal that may depend upon one or more parameters q and that is periodic with period kΔ
τ
hd chip, where k is a selected integer≧
2;(4) selecting an integer n≧
3 and setting an accumulation An-1 =0;(5) examining the bit value bn, for the time interval defined by nΔ
τ
chip ≦
t≦
(n+1)Δ
τ
chip, and the two immediately preceding digital bit values bn-1 and bn-2 of the reference signal Sd (t);(6) when bn-2 =bn-1 and bn-1 ≠
bn, computing the contribution of the first signal product difference over a time interval In ={t'"'"'|tn-1 +Δ
<
t'"'"'≦
tn +Δ
}, where Δ
is a selected time value satisfying 0≦
Δ
<
Δ
τ
chip, to an autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this contribution to An-1 to form An ;(7) when bn-2 ≠
bn-1 or bn-1 =bn, computing the contribution of the second signal product difference over the time interval In to the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t), and adding this integral or sum to An-1 to form An ;(8) replacing the integer n by the integer n+1 and repeating steps (5), (6) and (7) at least once; (9) interpreting the accumulation AN for a selected positive integer N as the autocorrelation difference function Δ
AC#(τ
;
q) for the incoming digital signal s(t); and(10) determining at least one value t0 of the time shift variable τ
for which the autocorrelation difference function Δ
AC#(τ
;
q) changes sign; and(11) interpreting the time value t=t0 as an estimate of the time at which a signal, that is substantially free of the presence of a multipath signal, was received.
-
Specification