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Active antenna

  • US 5,296,866 A
  • Filed: 07/29/1991
  • Issued: 03/22/1994
  • Est. Priority Date: 07/29/1991
  • Status: Expired due to Fees
First Claim
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1. An active antenna including an antenna, a feedback winding, and circuit means:

  • said antenna having positive inductance and positive resistance, including any impedances coupled into said antenna from the environment, said antenna being field coupled to said feedback winding;

    said circuit means including an operational amplifier and a voltage-controlled current source, the output of said operational amplifier connected to said voltage-controlled current source, said circuit means providing a negative inductance and a negative resistance, the magnitude of said negative inductance being on the order of said antenna positive inductance but somewhat less, and the magnitude of said negative resistance being on the order of said antenna positive resistance but somewhat less;

    means to connect the antenna and said circuit means in a configuration which provides an algebraic addition of said positive and negative inductances and resistances, with the total active antenna circuit impedance being a very small, but positive, series inductance and resistance;

    said antenna being connected to the inverting input of said operational amplifier, and said voltage-controlled current source being controlled by the output of said amplifier and providing current to said feedback winding.

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