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Noise inverter circuit for a power line communication system

  • US 4,609,839 A
  • Filed: 10/01/1984
  • Issued: 09/02/1986
  • Est. Priority Date: 10/01/1984
  • Status: Expired due to Term
First Claim
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1. A noise inverter circuit for a power line communication system comprising:

  • first and second input terminals for receiving an alternating current electrical communication signal voltage which may include impulse noise;

    third and fourth output terminals for providing an output alternating current electrical communication signal voltage, said second input terminal and said fourth output terminal being connected in common;

    first and second oppositely polled capacitors each connected at one end thereof to said first input terminal;

    first and second diodes each having an anode and a cathode, the cathode of said first diode being connected to the other end of said first capacitor and the anode of said second diode being connected to the other end of said second capacitor;

    a first resistor connected at one end to the anode of said first diode and the cathode of said second diode and at the other end to the common connection of said second input terminal and the fourth output terminal, said first and second capacitors charging through said first and second diodes, respectively, and said first resistor to the prevailing peak signal voltage on alternate polarity peaks;

    a second resistor connected between said first and second capacitors to provide a discharge path therebetween;

    a third resistor connected between said first input terminal and said third output terminal for limiting the peak voltage across said first and second capacitors and reducing the peak output voltage across said third and fourth output terminals; and

    first and second transistors of opposite conductivity type each having a base, collector and emitter, the collectors of said first and second transistors being connected in common to said third output terminal, the emitters of said first and second transistors being connected to the common connection of said second input terminal and said fourth output terminal, the base of said first transistor being connected to the cathode of said first diode, and the base of said second transistor being connected to the anode of said second diode, whereby said first and second transistors are biased into conduction on alternate polarity peaks for signal voltages above a predetermined amplitude to thereby invert the peak amplitudes to a value less than the signal amplitude.

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