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Spread-spectrum receiver with progressive fourier transform

  • US 7,227,884 B2
  • Filed: 07/31/2002
  • Issued: 06/05/2007
  • Est. Priority Date: 02/28/2000
  • Status: Active Grant
First Claim
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1. A communications system for receiving a plurality of messages from a plurality of transmitters that each use a common spreading code, comprising:

  • a receiver that is configured to receive a composite signal that comprises the plurality of messages from the plurality of transmitters, each message having a transmitter code-phase relative to a code-phase of the receiver, each transmitter code-phase being independent of the code-phase of the receiver, anda message discriminator that is configured to;

    discriminate at least one message from the plurality of messages based on the transmitter code-phase corresponding to the at least one message, andsearch each frequency of a plurality of frequencies for energy content at each code-phase of a plurality of code-phases to discriminate the at least one message at the transmitter code-phase, wherein;

    the message discriminator comprises;

    a detector that is configured to determine a measure of the energy content at each code-phase at a given frequency of the plurality of frequencies, and to identify one or more code-phases at the given frequency, based on the measure of the energy content,a demodulator, operably coupled to the detector, that is configured to demodulate an input signal corresponding to the composite signal, based on at least one of the identified one or more code-phases at the given frequency,the receiver is configured to provide a downconverted composite signal at a baseband frequency of the plurality of messages, andthe detector determines the measure of the energy content at each code-phase based on a Fourier Transform that is applied to the downconverted composite signal at one or more given frequencies.

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