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Phase modulation compensated amplitude modulator using digitally selected amplifiers

  • US 4,952,890 A
  • Filed: 09/12/1989
  • Issued: 08/28/1990
  • Est. Priority Date: 09/12/1989
  • Status: Expired due to Term
First Claim
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1. A phase modulation compensated RF amplitude modulated amplifier system comprising:

  • a common RF driver for supplying a common RF driver signal;

    a plurality of actuatable RF amplifiers each having an input circuit for receiving said common RF drive signal and each having a fully on condition for amplifying said common drive signal to provide an amplified RF signal and a fully off condition, with each said RF amplifier exhibiting the characteristic that its input circuit has an input impedance which is greater when fully on than that when fully off, thereby tending to provide unwanted phase modulation of said plurality of RF amplifiers;

    means for actuating a selected one or more of said RF amplifiers to be fully on in dependence upon the magnitude of an input signal;

    means for combining said amplified RF signals provided by the selected actuated ones of said RF amplifiers to thereby provide a combined signal which is amplitude modulated in accordance with the magnitude of said input signals; and

    ,means for selectively adding a compensating impedance to the input circuit of each of said amplifiers that is not actuated to be fully on to thereby compensate for any said unwanted phase modulation of said plurality of RF amplifiers.

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