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Proximity detecting apparatus

  • US 4,621,258 A
  • Filed: 08/22/1983
  • Issued: 11/04/1986
  • Est. Priority Date: 08/22/1983
  • Status: Expired due to Fees
First Claim
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1. Apparatus for detecting an intrusion of an ambient electromagnetic field of an antenna, in the presence of radiation about said antenna that produce voltages on the antenna for providing an indication of the intrusion of said electromagnetic field;

  • an antenna capable of receiving said electromagnetic radiation and having a voltage generated therein by said radiation and wherein there is a change in level of voltage so generated which will be above or below the level where there is no intrusion,a first amplifier for receiving said alternating current voltages at said levels and for producing a direct current voltage fluctuation at the same frequency as said alternating current voltage, but at a level elevated from that of the alternating current voltage;

    filtering means for receiving said direct current fluctuations and for producing a constant direct current voltage at a level responsive to each change in level of the fluctuating direct current voltage;

    a second amplifier receiving changes in level of said constant voltage to produce a negative or positive going square wave voltage pulse, constant in amplitude;

    a third amplifier responsive only to the negative going square wave voltage pulses to produce a positive going square wave voltage pulse;

    a fourth amplifier for receiving the output from said third amplifier having means there between whereby response of said fourth amplifier can be selectively made responsive to a single square wave voltage pulse or to a square wave voltage pulse produced after the occurrence of a plurality of square wave voltage pulses; and

    means receiving the output of said fourth amplifier for triggering an indication of said intrusion.

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