Low noise, electric field sensor
First Claim
Patent Images
1. A system for measuring a free space electric field, said system comprising:
- a ground connection;
an ultrahigh impedance antenna positioned in the electric field for generating a signal from the electric field;
an amplifier having an input port and an output port, wherein said amplifier generates an input bias current, said input bias current being combined with the signal to create an input potential at the input port;
an electrical circuit connected to said input port and said ground connection, said electrical circuit having at least one circuit element for controlling said input potential to stabilize said signal at said input port; and
a means connected between the output port and the input port for generating negative feedback for said amplifier below a selected cutoff frequency.
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Abstract
A system for measuring a free space electric field includes an ultrahigh impedance antenna positioned in the electric field to generate a signal from the electric field. An amplifier having an input port is provided to amplify the signal. The amplifier generates an input bias current which combines with the signal to create an input potential at the input port. An electrical circuit connects the input port to a ground connection and includes at least one circuit element for controlling the input potential to stabilize the signal at the input port.
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Citations
16 Claims
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1. A system for measuring a free space electric field, said system comprising:
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a ground connection; an ultrahigh impedance antenna positioned in the electric field for generating a signal from the electric field; an amplifier having an input port and an output port, wherein said amplifier generates an input bias current, said input bias current being combined with the signal to create an input potential at the input port; an electrical circuit connected to said input port and said ground connection, said electrical circuit having at least one circuit element for controlling said input potential to stabilize said signal at said input port; and a means connected between the output port and the input port for generating negative feedback for said amplifier below a selected cutoff frequency. - View Dependent Claims (2, 3, 4)
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5. A system for measuring a free space electric field, said system comprising:
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a ground connection; an ultrahigh impedance antenna positioned in the electric field for generating a signal from the electric field; an amplifier having an input port and an output port, wherein said amplifier generates an input bias current, said input bias current being combined with the signal to create an input potential at the input port; an electrical circuit connected to said input port and said ground connection, said electrical circuit having at least one circuit element for controlling said input potential to stabilize said signal at said input port; and a means connected between the output port and the input port for generating high gain negative feedback for said amplifier below a selected cutoff frequency and substantially no feedback above said selected cutoff frequency.
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6. A system for measuring a free space electric field, said system comprising:
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a ground connection; an ultrahigh impedance antenna positioned in the electric field for generating a signal from the electric field; an amplifier having an input port and an output port, wherein said amplifier generates an input bias current, said input bias current being combined with the signal to create an input potential at the input port; an electrical circuit connected to said input port and said ground connection, said electrical circuit having at least one circuit element for controlling said input potential to stabilize said signal at said input port; and a means connected between the output port and the input port for generating a high gain negative feedback for said amplifier below a first selected cutoff frequency ν
1, a high gain negative feedback for said amplifier above a second selected cutoff frequency ν
2, and substantially no feedback at frequencies between ν
1 and ν
2.
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7. A system for measuring a free space electric field, said system comprising:
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a ground connection; an ultrahigh impedance antenna positioned in the electric field for generating a signal from the electric field; an amplifier having an input port, an output port and an input capacitance at the input port, wherein said amplifier generates an input bias current, said input bias current being combined with the signal to create an input potential at the input port; and an electrical circuit connected to said input port and said ground connection, said electrical circuit having at least one circuit element for controlling said input potential to stabilize said signal at said input port and a means connected between the output port and the input port for eliminating the effect of said input capacitance of said amplifier. - View Dependent Claims (8, 9)
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10. A system for measuring a free space electric field, said system comprising:
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a ground connection; an antenna positioned in the electric field for generating a substantially a.c. signal from the electric field; an amplifier having an input port and an output port, wherein said amplifier generates a substantially d.c. input bias current, said d.c. input bias current being combined with the a.c. signal to create an input potential at the input port; an electrical circuit connected to said input port and said ground connection, said electrical circuit having at least one circuit element for draining said d.c. input potential to said ground connection to stabilize said a.c. signal at said input port; and a means connected between the output port and the input port for generating negative feedback for said amplifier below a selected cutoff frequency. - View Dependent Claims (11, 12)
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13. A system for measuring a free space electric field, said system comprising:
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a ground connection; an antenna positioned in the electric field for generating a substantially a.c. signal from the electric field; an amplifier having an input port, an output port and an input capacitance at the input port, wherein said amplifier generates a substantially d.c. input bias current, said d.c. input bias current being combined with the a.c. signal to create an input potential at the input port; an electrical circuit connected to said input port and said ground connection, said electrical circuit having at least one circuit element for draining said d.c. input potential to said ground connection to stabilize said a.c. signal at said input port; and a means connected between the output port and the input port for eliminating the effect of said input capacitance of said amplifier.
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14. A method for measuring a free space electric field, said method comprising the steps of:
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positioning an ultrahigh impedance antenna having an input capacitance in the electric field to generate a signal from the electric field; connecting said antenna to an input port of an amplifier, wherein said amplifier generates an input bias current, said input bias current being combined with the signal to create an input potential at the input port; connecting an electrical circuit to said input port and to a ground connection, said electrical circuit having at least one circuit element for controlling said input potential to stabilize said signal at said input port; generating negative feedback for said amplifier below a selected cutoff frequency; and eliminating the effect of said input capacitance of said amplifier. - View Dependent Claims (15, 16)
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Specification