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Data transmission via multi-path channels using orthogonal multi-frequency signals with differential phase shift keying modulation

  • US 9,769,004 B2
  • Filed: 11/23/2015
  • Issued: 09/19/2017
  • Est. Priority Date: 10/05/2007
  • Status: Active Grant
First Claim
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1. A data communications system, for use over a multi-path channel, comprising:

  • an orthogonal frequency division multiplexing (OFDM) sub-carrier signal generator that outputs a plurality of OFDM sub-carrier signals;

    a differential quadrature phase shift keying (DQPSK) modulator that modulates each OFDM sub-carrier signal of the plurality of OFDM sub-carrier signals in response to input data, and forms a plurality of modulated OFDM sub-carrier signals in response to the input data;

    a summer that combines the plurality of modulated OFDM sub-carrier signals to form a transmitted signal;

    a receiver to output a received signal in response to the transmitted signal transmitted through the multi-path channel, the received signal having a missing sub-carrier signal at a center frequency located in the middle of a frequency spectrum of the received signal, the missing sub-carrier signal having zero amplitude;

    an OFDM sub-carrier reference generator that outputs a plurality of OFDM sub-carrier reference signals, the plurality of OFDM sub-carrier reference signals including an OFDM sub-carrier reference signal located at the center frequency;

    a non-coherent synchronizer that synchronizes an OFDM symbol interval to a demodulating interval by nulling a correlation between the received signal and the OFDM sub-carrier reference signal located at the center frequency; and

    a demodulator, using a DQPSK multi-carrier detector, that demodulates the received signal to form an output signal.

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