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Feed forward amplifier

  • US 5,455,537 A
  • Filed: 08/19/1994
  • Issued: 10/03/1995
  • Est. Priority Date: 08/19/1994
  • Status: Expired due to Fees
First Claim
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1. A feed forward amplifier comprising:

  • a main amplifier coupled between an input at which an input signal is received and an output at which an output signal is provided, said output signal being an amplification of said input signal, and said main amplifier being responsive to said input signal for providing an amplified input signal;

    sampling means responsive to said amplified input signal for providing a sample of said amplified input signal;

    comparison means for comparing said sample of said amplified input signal with a sample of said input signal to produce a difference signal indicative of distortions introduced by said main amplifier;

    an error amplifier responsive to said difference signal for providing a distortion signal which is an amplification of said difference signal;

    combiner means for combining said distortion signal with said amplified input signal to provide said output signal, thereby compensating for said distortions;

    means for combining a variable frequency, constant peak amplitude pilot signal in an input signal path between said input and said sampling means;

    a correlation power detector having;

    (a) coupler means responsive to a sample of said output signal for providing a pair of sample signals having equal amplitude and ninety (90) degrees phase difference;

    (b) a pair of mixers, each mixer being responsive to a sample of said pilot signal and to one of said sample signals for providing a multiplication signal, each multiplication signal being the product of said sample of said pilot signal and one of said sample signals;

    (c) a pair of averaging circuit means each responsive to one of said multiplication signals for providing an averaged signal, each averaged signal being respectively indicative of the average of a corresponding multiplication signal;

    (d) means for providing a pilot signal power signal as the sum of the squares of said averaged signals, said pilot signal power signal being indicative of the magnitude of said pilot signal in said output signal; and

    means responsive to said pilot signal power signal for adjusting the gain and phase of said difference signal to minimize the magnitude of said pilot signal power signal.

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