US5357253A — System and method for earth probing with deep sub…

Claim 1

Independent Claim 118 words

A system for earth exploration by generating and radiating low frequency electromagnetic energy deeply into the earth and analyzing return information, the system comprising: a) means for generating a series of pulsed electromagnetic signals in a low frequency range less than about 3 Megahertz, so as to form a series of electromagnetic pulses having respective spectra which collectively cover a portion of the low frequency range that is substantially larger than any individual pulse's spectrum; b) means for radiating the electromagnetic pulses into the earth, so as to penetrate the earth to substantial depths; c) means for detecting electromagnetic reflections from subsurface layers or objects; and d) means for extracting deep subsurface return information from the electromagnetic reflections.

Claim 2

Independent Claim 118 words

A system for earth exploration by generating and radiating low frequency electromagnetic energy deeply into the earth and analyzing return information, the system comprising: a) means for generating a series of pulsed electromagnetic signals in a low frequency range less than about 3 Megahertz, so as to form a series of electromagnetic pulses having respective spectra which collectively cover a portion of the low frequency range that is substantially larger than any individual pulse's spectrum; b) means for radiating the electromagnetic pulses into the earth, so as to penetrate the earth to substantial depths; c) means for detecting electromagnetic reflections from subsurface layers or objects; and d) means for extracting deep subsurface return information from the electromagnetic reflections.

Claim 3

Dependent Claim 22 words

The system of claim 1, wherein the extracting means includes: means for removing system distortions such as detecting-device bias and compensation errors.

Claim 4

Dependent Claim 32 words

The system of claim 1, wherein the generating means constitutes means for generating electromagnetic energy in a series of pulsed electromagnetic signals having frequencies in a range from 0.3 to 3,000 Kilohertz.

Claim 5

Dependent Claim 38 words

The system of claim 1, wherein the generating means constitutes means for generating electromagnetic energy in a series of pulses having energies in excess of 300,000 joules per sounding, each sounding corresponding to the series of electromagnetic pulses.

Claim 6

Dependent Claim 130 words

The system of claim 1, wherein: a) the means for detecting includes: 1) a first receiving antenna; and 2) a second receiving antenna; b) the extracting means includes means for automatically compensating for direct leakage from the generating means by using a spatial notching technique, the compensating means including a combiner, responsive to signals received by the first and second antennas; c) the first and second receiving antennas are positioned relative to the generating means so that the combiner combines (1) attenuated versions of direct signals received by the first receiving antenna with (2) signals derived from those signals received by the second receiving antenna; and d) the combiner cancels portions of the signals received by the second receiving antenna that are due to direct transmission from the generating means.

Claim 7

Dependent Claim 55 words

The system of claim 1, wherein the extracting means includes means for switching automatically between: (1) a DC bias adjustment position, in which reflection signals are gated off; and (2) a long time integration position, in which the reflection signals are gated on for removal of interference that would otherwise mask weak return information signals.

Claim 8

Dependent Claim 37 words

The system of claim 1, wherein the extracting means includes: means for integrating a signal derived from the electromagnetic reflections during a pulse period, so as to remove interference that would otherwise mask weak return information signals.

Claim 9

Dependent Claim 53 words

The system of claim 5, wherein the extracting means further includes: vector calibration and error removal means for (1) determining a reference vector derived from signals from the first receiving antenna, and (2) removing phase and amplitude error from a signal derived from signals from the second receiving antenna by using vector operations.

Claim 10

Dependent Claim 46 words

The system of claim 1, wherein the extracting means includes: means for applying a low side-lobe weighting function to a signal derived from the electromagnetic reflections, so as to allow extraction of weak subsurface return information even in the presence of strong surface or subsurface reflections.

Claim 11

Dependent Claim 32 words

The system of claim 1, wherein the extracting means includes: means for applying an Inverse Fast Fourier Transform so as to convert signals derived from the electromagnetic reflections to corresponding depth signals.

Claim 12

Dependent Claim 32 words

The system of claim 1, wherein the extracting means includes: means for applying a depth sensitivity compensation function so as to compensate for reduced-magnitude signals reflected from deeper subsurface layers or objects.

Claim 13

Dependent Claim 27 words

The system of claim 1, further comprising: a recorder means for obtaining depth profiles and a stacking arrangement, so as to form three-dimensional images of subsurface structures.

Claim 14

Dependent Claim 15 words

The system of claim 1, further comprising: means for displaying depth images of subsurface structures.

Claim 15

Dependent Claim 173 words

A deep probing radar generating and radiating system for use in obtaining reflected signal data to permit mapping of layers or objects beneath the surface of the earth or other media, the system comprising: a) means for generating pulses of high power electromagnetic waves of various respective frequencies, each frequency being in a low frequency range of less than about 3 MHz; b) a transmitting antenna which is small in comparison to the electromagnetic waves' wavelengths, the transmitting antenna responsive to the generating means to radiate the pulses of electromagnetic waves deeply into the earth or other media; c) timing means for controlling the frequency of the waves generated by the generating means so as to cause respective frequency spectra of the pulses to collectively cover a substantial percentage of the low frequency range; and d) means for tuning the transmitting antenna to resonance in response to a control signal from the timing means so as to generate the high power pulses, the control signal changing between at least some of the pulses.

Claim 16

Dependent Claim 173 words

A deep probing radar generating and radiating system for use in obtaining reflected signal data to permit mapping of layers or objects beneath the surface of the earth or other media, the system comprising: a) means for generating pulses of high power electromagnetic waves of various respective frequencies, each frequency being in a low frequency range of less than about 3 MHz; b) a transmitting antenna which is small in comparison to the electromagnetic waves' wavelengths, the transmitting antenna responsive to the generating means to radiate the pulses of electromagnetic waves deeply into the earth or other media; c) timing means for controlling the frequency of the waves generated by the generating means so as to cause respective frequency spectra of the pulses to collectively cover a substantial percentage of the low frequency range; and d) means for tuning the transmitting antenna to resonance in response to a control signal from the timing means so as to generate the high power pulses, the control signal changing between at least some of the pulses.

Claim 17

Dependent Claim 25 words

The system of claim 14 wherein the generating means includes: a variable frequency power source connected to drive the transmitting antenna through the tuning means.

Claim 18

Dependent Claim 59 words

The system of claim 14 wherein the tuning means includes: plural means for switching a corresponding plurality of reactive circuit elements into and out of a circuit so as to alter the antenna circuit's resonant frequency to match the frequency of the pulses of electromagnetic waves, the switching means being controlled by the control signal from the timing means.

Claim 19

Dependent Claim 61 words

The system of claim 16, wherein: the control signal is a binary word having a plurality of bits; and the switching means constitute a number of switches arranged with respect to the corresponding reactive circuit elements so as to selectively switch each corresponding reactive circuit element into and out of the circuit in accordance with respective bits from the binary word.

Claim 20

Dependent Claim 12 words

The system of claim 17, wherein the reactive circuit elements are capacitors.

Claim 21

Dependent Claim 47 words

The system of claim 18, wherein: there are N capacitors having values C, 2C, . . . 2.sup.(N-1) C, so that an aggregate capacitance of any integral multiple of a single capacitance C can be achieved by selectively switching the capacitors into and out of the circuit.

Claim 22

Dependent Claim 12 words

The system of claim 17, wherein the reactive circuit elements are inductors.

Claim 23

Dependent Claim 44 words

The system of claim 20, wherein: there are N inductors having values L, L/2, . . . L/2.sup.(N-1), so that an aggregate inductance, L divided by any integer through N-1, can be formed by selectively switching the inductors into and out of the circuit.

Claim 24

Dependent Claim 13 words

The system of claim 14, wherein the transmitting antenna is a loop antenna.

Claim 25

Dependent Claim 13 words

The system of claim 14, wherein the transmitting antenna is a dipole antenna.

Claim 26

Dependent Claim 38 words

The system of claim 14, wherein the timing means includes means for synchronizing operations of: (1) changing the frequency of the pulsed signals generated by the generating means; with (2) sending of control signals to the tuning means.

Claim 27

Dependent Claim 30 words

The system of claim 14, wherein the timing means includes means for controlling the generating means to generate a series of pulses of consecutively higher frequency within the frequency range.

Claim 28

Dependent Claim 35 words

The system of claim 14, further comprising: means for monitoring the amplitude and phase of the electromagnetic waves radiated from the antenna, so as to allow compensating for deviations in frequency, spurious signals and noise.

Claim 29

Dependent Claim 20 words

The system of claim 26, wherein the monitoring means includes: a second antenna located physically close to the transmitting antenna.

Claim 30

Dependent Claim 31 words

The system of claim 26, further comprising: a processing means for receiving a signal from the monitoring means and causing the timing means to alter operating parameters of the generating means.

Claim 31

Dependent Claim 104 words

A receiver subsystem for use in a system for earth probing having a transmitting antenna, the receiver comprising: a) first and second receiving antennas for producing respective first and second antenna output signals, the first receiving antenna positioned much closer to the transmitting antenna than the second receiving antenna; b) means for attenuating the first antenna output signal to produce an attenuated signal; and c) means for combining signals derived from the attenuated signal and the second antenna output signal, so as to substantially remove signal components from the second antenna output signal that are caused by direct signal transmission from the transmitting antenna.

Claim 32

Dependent Claim 104 words

A receiver subsystem for use in a system for earth probing having a transmitting antenna, the receiver comprising: a) first and second receiving antennas for producing respective first and second antenna output signals, the first receiving antenna positioned much closer to the transmitting antenna than the second receiving antenna; b) means for attenuating the first antenna output signal to produce an attenuated signal; and c) means for combining signals derived from the attenuated signal and the second antenna output signal, so as to substantially remove signal components from the second antenna output signal that are caused by direct signal transmission from the transmitting antenna.

Claim 33

Dependent Claim 24 words

The subsystem of claim 29, wherein the combining means includes a subtractor means for subtracting the attenuated signal from the second antenna output signal.

Claim 34

Dependent Claim 146 words

A receiver subsystem for use in a system for earth probing having a transmitter driving a transmitting antenna at a band of frequencies, the receiver comprising: a) first and second receiving antennas for producing respective first and second antenna output signals, the first receiving antenna positioned much closer to the transmitting antenna than the second antenna; b) first and second amplitude and phase detectors, connected to receive the respective first and second antenna output signals and provide respective first and second detector outputs expressed as respective first and second complex numbers; and c) means for dividing the second complex number by the first complex number to provide a quotient complex number which contains accurate information regarding subsurface reflections of transmitted energy but is compensated for frequency-dependent amplitude and phase variations of the transmitter, variations in earth loading and changes in antenna operating height above the ground.

Claim 35

Dependent Claim 146 words

A receiver subsystem for use in a system for earth probing having a transmitter driving a transmitting antenna at a band of frequencies, the receiver comprising: a) first and second receiving antennas for producing respective first and second antenna output signals, the first receiving antenna positioned much closer to the transmitting antenna than the second antenna; b) first and second amplitude and phase detectors, connected to receive the respective first and second antenna output signals and provide respective first and second detector outputs expressed as respective first and second complex numbers; and c) means for dividing the second complex number by the first complex number to provide a quotient complex number which contains accurate information regarding subsurface reflections of transmitted energy but is compensated for frequency-dependent amplitude and phase variations of the transmitter, variations in earth loading and changes in antenna operating height above the ground.

Claim 36

Dependent Claim 204 words

A receiver subsystem for use in a system for earth probing having a transmitter and an associated transmitting antenna, the receiver comprising: a) first and second receiving antennas for producing respective first and second antenna output signals, the first receiving antenna positioned much closer to the transmitting antenna than the second receiving antenna; b) means for attenuating the first antenna output signal to produce an attenuated signal; c) means for combining signals derived from the attenuated signal and the second antenna output signal, so as to substantially remove signal components from the second antenna output signal that are caused by direct signal transmission from the transmitting antenna, the combining means providing a combiner output; d) first and second amplitude and phase detectors, connected to receive the combiner output and the attenuator output, respectively, and provide respective first and second detector outputs expressed as respective first and second complex numbers; and e) means for dividing the second complex number by the first complex number to provide a quotient complex number which contains accurate information regarding subsurface reflections of transmitted energy but is compensated for frequency-dependent amplitude and phase variations of the transmitter, variations in earth loading and changes in antenna operating height above the ground.

Claim 37

Dependent Claim 204 words

A receiver subsystem for use in a system for earth probing having a transmitter and an associated transmitting antenna, the receiver comprising: a) first and second receiving antennas for producing respective first and second antenna output signals, the first receiving antenna positioned much closer to the transmitting antenna than the second receiving antenna; b) means for attenuating the first antenna output signal to produce an attenuated signal; c) means for combining signals derived from the attenuated signal and the second antenna output signal, so as to substantially remove signal components from the second antenna output signal that are caused by direct signal transmission from the transmitting antenna, the combining means providing a combiner output; d) first and second amplitude and phase detectors, connected to receive the combiner output and the attenuator output, respectively, and provide respective first and second detector outputs expressed as respective first and second complex numbers; and e) means for dividing the second complex number by the first complex number to provide a quotient complex number which contains accurate information regarding subsurface reflections of transmitted energy but is compensated for frequency-dependent amplitude and phase variations of the transmitter, variations in earth loading and changes in antenna operating height above the ground.

Claim 38

Dependent Claim 24 words

The subsystem of claim 32, wherein the combining means includes a subtractor means for subtracting the attenuated signal from the second antenna output signal.

Claim 39

Dependent Claim 31 words

The subsystem of claim 32, further comprising: processing means for receiving a signal from the first antenna so as to allow the processor means to control the transmitter's amplitude and phase.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-10-17	1998-04-18	1998-10-18	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-10-17	2002-04-18	2002-10-18	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-10-17	2006-04-18	2006-10-18	$7700.00	Window Closed / Lapsed

System and method for earth probing with deep subsurface penetration using low frequency electromagnetic signals

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag