Method for mitigating multipath effects in radio ranging systems
First Claim
1. A process for providing an optimal estimate of range in a signal ranging system, comprising the steps of:
- receiving a transmitted signal having ranging information contained therein and including a secondary path signal, and translating a combined received signal to a baseband signal;
sampling the baseband signal synchronously with a modulation waveform creating a sampled baseband signal and combining successive repetitions of a plurality of range bearing information features of the sampled baseband signals;
correlating the combined sampled baseband signals and a plurality of artificially delayed representations of a known transmitted signal creating a plurality of received signal representations based on the range bearing information features of the sampled baseband signals;
computing a maximum likelihood estimate of range using selected pairs of received signal representations;
constraining the relative amplitude of the secondary path signal estimate based on knowledge of the transmitted signal environment; and
computing a second maximum likelihood estimate of range while constraining the relative amplitude of the secondary path signal using the received signal representations.
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Accused Products
Abstract
This invention involves a method for mitigating multipath effects in radio ranging systems which is based on searching for and finding a maximum likelihood estimate of range for a received signal in a signal ranging system. In determining the maximum likelihood estimate, the correlation process uses a high resolution step method in processing the received signal sample values to develop an estimation statistic. The estimation statistic using the correlations of the received signal is based on a new derived representative set of coefficients formed from a nonlinear combination of parameters of the received signal transformed into an invertible linear combination which allows solution of the maximization process of the estimation statistic. Additionally there is a method of constraining the relative amplitude of received secondary signals to obtain a refinement of the optimal solution of range. Also the method includes a process to reduce the magnitude of the processing required by the receiver by reducing the size of the overall sample of the signal that must be managed by the receiver. The method may be used in a signal environment where multiple secondary path signals are received by the signal ranging system.
34 Citations
8 Claims
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1. A process for providing an optimal estimate of range in a signal ranging system, comprising the steps of:
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receiving a transmitted signal having ranging information contained therein and including a secondary path signal, and translating a combined received signal to a baseband signal; sampling the baseband signal synchronously with a modulation waveform creating a sampled baseband signal and combining successive repetitions of a plurality of range bearing information features of the sampled baseband signals; correlating the combined sampled baseband signals and a plurality of artificially delayed representations of a known transmitted signal creating a plurality of received signal representations based on the range bearing information features of the sampled baseband signals; computing a maximum likelihood estimate of range using selected pairs of received signal representations; constraining the relative amplitude of the secondary path signal estimate based on knowledge of the transmitted signal environment; and computing a second maximum likelihood estimate of range while constraining the relative amplitude of the secondary path signal using the received signal representations. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A process for providing a reduced set of correlation values for a signal ranging system range estimate, comprising the steps of:
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sampling of a received signal having a code modulation signal with range bearing information features including a secondary signal component at each modulation waveform transition region using a priori knowledge of a known transmitted signal wherein the sampling at the modulation waveform transition regions uses only a small subset of the received signal in code information; averaging corresponding modulation waveform transition region samples based on statistical success of sampling relative to the range bearing information features including the secondary signal component, over a selected averaging interval; and providing an averaged sample signal to a correlation processor.
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Specification