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Near direct conversion receiver and method for equalizing amplitude and phase therein

  • US 5,828,955 A
  • Filed: 08/30/1995
  • Issued: 10/27/1998
  • Est. Priority Date: 08/30/1995
  • Status: Expired due to Term
First Claim
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1. A receiver including:

  • (a) a downconversion means for receiving a radio frequency (RF) signal and downconverting said RF signal to an in-phase intermediate frequency (IF) signal (IFI) and a quadrature-phase IF signal (IFQ); and

    (b) processing means, operatively coupled to said downconversion means, and including a pair of analog-to-digital converters for digitizing the IFI and IFQ signals, and a digital signal processor (DSP), operatively coupled to said analog-to-digital converters, for correcting the digitized IF signals (IFI, IFQ) so that they are substantially equal in magnitude and substantially 90°

    out of phase, and then downconverting said digitized IF signals to baseband signals (I, Q), wherein said DSP includes phase correcting means including;

    (1) a phase shifter for phase shifting at least one of said IF signals and providing as a phase shifter output phase shifted representations of said at least one of said IF signals;

    (2) a multiplier, operatively coupled to said phase shifter, for multiplying said IF signals and providing as a multiplier output product signals representing products of said IF signals; and

    (3) an integrator, operatively coupled to said multiplier and said phase shifter, for summing said product signals, providing sum signals representing cumulative sums of said product signals, and feeding said sum signals back to said phase shifter;

    wherein said phase shifter shifts the phase of said at least one of said IF signals so as to minimize any error in the quadrature-phase relationship between the IFI and IFQ signals,wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal.

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