Spread spectrum receiver with multi-path cancellation
First Claim
1. A spread spectrum receiver, comprising:
- means for forming a composite of direct path and multipath coded spread spectrum signal components from a plurality of satellites;
means for generating a model of the direct path and multipath signal components from a selected one of the satellites; and
means responsive to the direct path component of the model for deriving information from the composite related to the selected satellite.
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Accused Products
Abstract
A terrestrial C/A code GPS receiver system digitally samples, filters and stores a segment of 11 half chips of the received composite as a binary number and multiplexes this number for parallel correlation with each of a series of multibit code replicas for the satellites to be tracked. Multipath interference is canceled by deriving code phase timing from a model of the signal being tracked in each satellite channel. The model includes weighted, time delayed components of a plurality of time shifted versions of the code. A feedback control loop is used to match the amplitude profile of the model to the amplitude profile of the signal as received. The earliest version of the code having significant amplitude components may be used as the prompt code or the prompt code phase may be selected to be between the first and second versions of the code having significant amplitude components.
217 Citations
19 Claims
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1. A spread spectrum receiver, comprising:
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means for forming a composite of direct path and multipath coded spread spectrum signal components from a plurality of satellites; means for generating a model of the direct path and multipath signal components from a selected one of the satellites; and means responsive to the direct path component of the model for deriving information from the composite related to the selected satellite. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of operating a spread spectrum receiver in the presence of multipath signal interference comprising the steps of:
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tracking spread spectrum signals with a model of multipath and direct path components of the signals from a selected source; and correlating the spread spectrum signals as received with a replica of the direct path components of said model. - View Dependent Claims (12, 13, 14, 15)
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16. A method of processing GPS signals in a multipath environment, comprising the steps of:
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applying a digital representation of a composite of spread spectrum signals received from a plurality of satellites to a satellite specific carrier tracking channel including carrier phase rotation and code correlation at a code phase; and deriving the code phase by analysis of the composite before code correlation. - View Dependent Claims (17, 18, 19)
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Specification