DC & AC coupled E-field sensor
First Claim
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1. An E-field sensor comprising:
- an E-field sensing antenna;
a high input impedance amplifier having an input signal input, and an output signal output;
means coupling the E-field sensing antenna to the input signal input to supply an input signal from the E-field sensing antenna to the input signal input while substantially limiting any bias current flow at the input signal input to thereby tend to create a DC offset in an output signal at the output signal output of the amplifier; and
means for establishing a substantially DC reference signal coupled to the input signal from the E-field sensing antenna to produce a desired DC level on the input signal which affects operation of the amplifier to modify the DC offset in the output signal.
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Abstract
A method and apparatus is shown for detecting with high sensitivity by allowing the operation of an e-field amplifier without a DC bias resistor shunt with the amplifier input. E-fields produced by an approaching body, or changing E-field of the background, turn on the amplifier from a partial DC bias state with E-field coupling to the power supply of the amplifier. The result is high sensitivity and extremely long battery life. The amplifier is sensitive to transient and quasitatic DC E-field and the AC background signals. The signals are available simultaneously for processing at the output of the amplifier in a DC and AC coupled channel. The resulting signals are passed to a control system.
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Citations
14 Claims
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1. An E-field sensor comprising:
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an E-field sensing antenna; a high input impedance amplifier having an input signal input, and an output signal output; means coupling the E-field sensing antenna to the input signal input to supply an input signal from the E-field sensing antenna to the input signal input while substantially limiting any bias current flow at the input signal input to thereby tend to create a DC offset in an output signal at the output signal output of the amplifier; and means for establishing a substantially DC reference signal coupled to the input signal from the E-field sensing antenna to produce a desired DC level on the input signal which affects operation of the amplifier to modify the DC offset in the output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An E-field sensor comprising:
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an E-field sensing antenna; a high input impedance amplifier having an input signal input, and an output signal output; means coupling the E-field sensing antenna to the input signal input to supply an input signal from the E-field sensing antenna to the input signal input while substantially limiting any bias current flow at the input signal input to thereby tend to create a DC offset in an output signal at the output signal output of the amplifier; and means for establishing a reference signal coupled to the input signal from the E-field sensing antenna that will affect the input signal in a predetermined way to affect operation of the amplifier, wherein the means for establishing a reference signal includes a reference antenna, and a reference signal source for producing a reference signal on the reference antenna, wherein the reference antenna and the E-field sensor antenna are configured and positioned with respect to one another to provide electrical coupling wherein the reference signal will affect the input signal; and
wherein the reference signal is a substantially DC voltage level which creates a substantially DC voltage level on the reference antenna to adjust the DC level of the input signal to the amplifier and affect the operation of the amplifier to modify the DC offset of the output signal. - View Dependent Claims (14)
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Specification