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Location system

  • US 9,261,581 B2
  • Filed: 05/26/2015
  • Issued: 02/16/2016
  • Est. Priority Date: 04/07/2011
  • Status: Active Grant
First Claim
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1. A system for transmitting information comprising:

  • a transmitter unit configured to transmit an ultrasound signal comprising (i) a signature comprising a first pattern which is PSK-encoded on a first carrier and a second pattern which is PSK-encoded on a second carrier, wherein the first and second carriers have the same frequency but wherein the second carrier is out of phase with first carrier, and wherein the second pattern is offset from the first pattern in time by a transmitter-specific offset, and (ii) a PSK-encoded message-bearing portion;

    a receiver unit configured to receive the ultrasound signal from the transmitter unit; and

    a processing subsystem configured;

    to use the first and second patterns in the received signal to characterise a motion-induced phase distortion in the received signal;

    to use said characterisation to compensate for motion-induced phase distortion in the message-bearing portion of the received signal, thereby generating a compensated signal; and

    to decode the message from the compensated signal.

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