Suppression of multipath signal effects
First Claim
1. A method for use in decoding a composite signal having a signal-distorting component, the method comprising the steps of:
- receiving a digital composite signal that can vary with time t and that has a digital signal bit period with a selected length Δ
τ
chip ;
generating a selected digital reference signal;
generating a first weighting signal that is not constant in time and that, when mixed with the reference signal and the composite signal, reduces the effect of presence of a signal-distorting component in the composite signal;
mixing the first weighting signal with the reference signal and the composite signal to produce a first correlation function that represents a first timing relationship between the composite signal and the reference signal;
generating a second weighting signal that is not constant in time and that, when mixed with the reference signal and the composite signal, reduces the effect of presence of a signal-distorting component in the composite signal;
mixing the second weighting signal with the reference signal and the composite signal to produce a second correlation function that is distinct from said first correlation function and that represents a second timing relationship between said composite signal and said reference signal; and
forming a correlation difference function Δ
AC(τ
) that is a difference between the first correlation function and the second correlation function, where τ
is a time shift variable that allows variation of at least one of the first timing relationship and the second timing relationship.
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Abstract
Method and apparatus for formation of an autocorrelation difference function of an incoming digital signal, with bit transition interval length Δτchip, that reduces the effects of presence of a multipath signal in an incoming composite signal. First and second autocorrelation functions AC(τ;E;qE) and AC(τ;L;qL) are formed with respective first and second selected time shift values τ=tE and τ=tL, which replicate an estimate of an autocorrelation function AC(τ;P;qP) at an intermediate time shift value τ=tP that satisfies tE <tP <tL with tL -tE <2Δτchip, and which depend upon one or more parameters qE and qL, respectively. Independently chosen, non-uniform weighting functions w1(t;qE) and w2(t;qL) are used for formation of the respective autocorrelation functions AC(τ;E;qE) and AC(τ;L;qL) that depend upon one or more parameters qE and qL. Reduction of non-multipath and/or noise effects is achieved by particular choices of weighting functions. The correlator spacing tL -tE may be narrow (e.g., ΔtL-E ≦0.3Δτchip) or may be any larger value, up to 2Δτchip, with appropriate choice of the weighting functions w1 and w2.
25 Citations
26 Claims
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1. A method for use in decoding a composite signal having a signal-distorting component, the method comprising the steps of:
-
receiving a digital composite signal that can vary with time t and that has a digital signal bit period with a selected length Δ
τ
chip ;generating a selected digital reference signal; generating a first weighting signal that is not constant in time and that, when mixed with the reference signal and the composite signal, reduces the effect of presence of a signal-distorting component in the composite signal; mixing the first weighting signal with the reference signal and the composite signal to produce a first correlation function that represents a first timing relationship between the composite signal and the reference signal; generating a second weighting signal that is not constant in time and that, when mixed with the reference signal and the composite signal, reduces the effect of presence of a signal-distorting component in the composite signal; mixing the second weighting signal with the reference signal and the composite signal to produce a second correlation function that is distinct from said first correlation function and that represents a second timing relationship between said composite signal and said reference signal; and forming a correlation difference function Δ
AC(τ
) that is a difference between the first correlation function and the second correlation function, where τ
is a time shift variable that allows variation of at least one of the first timing relationship and the second timing relationship. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for use in decoding a composite signal having a signal-distorting component, the method comprising the steps of:
-
receiving a digital composite signal that can vary with time t and that has a digital signal bit period with a selected length Δ
τ
chip ;generating a selected digital reference signal; generating a first weighting signal that is not constant in time and that, when mixed with the reference signal and the composite signal, reduces the effect of presence of a signal-distorting component in the composite signal; mixing the first weighting signal with the reference signal and the composite signal to produce a first correlation function that represents a first timing relationship between the composite signal and the reference signal; generating a second weighting signal that is not constant in time and that, when mixed with the reference signal and the composite signal, reduces the effect of presence of a signal-distorting component in the composite signal, where the first weighting signal and the second weighting signal are equal to each other but may be shifted in time relative to each other; and mixing the second weighting signal with the reference signal and the composite signal to produce a second correlation fuinction that is distinct from said first correlation function and that represents a second timing relationship between said composite signal and said reference signal.
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14. Apparatus for use in decoding a composite signal having a signal-distorting component, the apparatus comprising:
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a signal antenna that receives an incoming composite signal that can vary with time t; a signal receiver/processor, including a computer, that receives the incoming signal from the signal antenna, that forms a digital composite signal, having a digital signal bit period with a selected length Δ
τ
chip, from the incoming composite signal, where the computer is programmed;to generate a selected digital reference signal; to generate a first weighting signal that is not constant in time and that, when mixed with the digital reference signal and the digital composite signal, reduces the effect of presence of a signal-distorting component in the composite signal; to mix the first weighting signal with the reference signal and the composite signal to produce a first correlation function that represents a first timing relationship between the composite signal and the reference signal; to generate a second weighting signal that is not constant in time and that, when mixed with the reference signal and the composite signal, reduces the effect of presence of a signal-distorting component in the composite signal; to mix the second weighting signal with the reference signal and the composite signal to produce a second correlation function that is distinct from the first correlation function and that represents a second timing relationship between the composite signal and the reference signal; and to form a correlation difference function Δ
AC(τ
) that is the difference between the first correlation function and the second correlation function, where τ
is a time shift variable that allows variation of at least one of the first timing relationship and the second timing relationship. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. Apparatus for use in decoding a composite signal having a signal-distorting component, the apparatus comprising:
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a signal antenna that receives an incoming composite signal that can vary with time t; a signal receiver/processor, including a computer, that receives the incoming signal from the signal antenna, that forms a digital composite signal, having a digital signal bit period with a selected length Δ
τ
chip, from the incoming composite signal, where the computer is programmed;to generate a selected digital reference signal; to generate a first weighting signal that is not constant in time and that, when mixed with the digital reference signal and the digital composite signal, reduces the effect of presence of a signal-distorting component in the composite signal; and to mix the first weighting signal with the reference signal and the composite signal to produce a first correlation function that represents a first timing relationship between the composite signal and the reference signal; to generate a second weighting signal that is not constant in time and that, when mixed with the reference signal and the composite signal, reduces the effect of presence of a signal-distorting component in the composite signal, where the first weighting signal and the second weighting signal are equal to each other but may be shifted in time relative to each other; and to mix the second weighting signal with said reference signal and said composite signal to produce a second correlation function that is distinct from said first correlation function and that represents a second timing relationship between said composite signal and said reference signal.
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Specification