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DS/CDMA receiver for high-speed fading environment

  • US 5,646,964 A
  • Filed: 07/08/1994
  • Issued: 07/08/1997
  • Est. Priority Date: 07/08/1993
  • Status: Expired due to Term
First Claim
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1. A receiver for a direct-sequence code division multiple access (DS/CDMA) communication system wherein a plurality of signal sources transmit DS/CDMA signals on a radio frequency carrier, each of the DS/CDMA signals being produced by spreading a symbol with a unique spread code at predetermined chip intervals, comprising:

  • receiver means having a spectral bandwidth for receiving said DS/CDMA signals;

    an interference canceller for cancelling signals from desired sources introduced to a signal received by the receiver means from a desired source by using a feedback signal;

    a phase variation canceller for cancelling a fading-related phase variation that occurs between successive symbols of the signal from the desired source;

    decision means for comparing an input signal with a decision threshold and producing an output signal representing one of two discrete values depending on whether the input signal is higher or lower than the threshold, the interference canceller and the phase variation canceller being connected in series between said receiver means and said decision means for producing an interference- and phase-variation-cancelled signal, andcorrection signal generator means for deriving a correction signal from said interference- and phase-variation cancelled signal and applying the correction signal to said interference canceller as said feedback signal,wherein the interference canceller is a linear equalizer including;

    a tapped-delay line having delay-line tap intervals equal to or smaller than said predetermined chip intervals;

    a plurality of multipliers connected to successive taps of the delay line for multiplying tap signals on said successive taps with respective tap weight vectors;

    an adder for summing outputs of the multipliers to produce a signal as an output signal of the interference canceller; and

    a tap-weight controller for deriving said tap weight vectors respectively from correlations between said tap signals and said feedback signal, whereby the tap weight vectors are orthogonally oriented to the signals from the undesired sources.

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