Radio geophysical surveying method and apparatus

Claim 2

In a method for radio geophysical surveying wherein a calibration signal of a predetermined frequency and containing substantially only vertically polarized signal components is transmitted from a transmitter, surface propagated, received on a first receiver adapted to receive vertically polarized signal components only and received on a second receiver adapted for receiving vertically and horizontally polarized signal components, and wherein a survey signal of said predetermined frequency and containing both vertically and horizontally polarized signal components is transmitted and is received by said receivers, said vertically polarized signal components being surface propagated and received by said first and second receivers and said horizontally polarized signal components being propagated into the earth and reflected to the surface by subterranean formations and received on said second receiver only, the improvement comprising the steps of: (a) obtaining signals proportional to said calibration signal from said first and second receivers; (b) applying said signals proportional to said calibration signal to a difference amplifier resulting in a calibration difference signal; (c) measuring and recording the magnitude of said calibration difference signal and the phase thereof relative to the signal from said first receiver; (d) obtaining signals proportional to said survey signal from said first and second receivers; (e) applying said signals proportional to said survey signal to said difference amplifier resulting in a survey difference signal; (f) measuring and recording the magnitude of said survey difference signal and the phase thereof relative to the signal proportional to said survey signal from said first receiver; (g) vectorially subtracting the magnitude and phase of said calibration difference signal from the magnitude and phase of said survey difference signal resulting in a relative magnitude and phase of said reflected signal components; (h) recording said relative magnitude and phase; (i) similarly obtaining a relative magnitude and phase at each of a plurality of positions along a survey path; and (j) plotting said relative magnitude and phase for each of said positions thereby obtaining a graph from which characteristics of said subterranean formations are ascertained.

Claim 3

A method as set forth in claim 1 wherein: (a) said transmitter includes a transmitting antenna adapted for radiating both vertically and horizontally polarized signal components and for emitting a radiation pattern including a horizontally directed electric field vector and a horizontally directed magnetic field vector; (b) said second receiver includes a receiving antenna having a response pattern similar to said radiation pattern; and including the steps of: (c) obtaining said relative magnitude and phase at each of said positions along said survey path with the respective electric field vectors of said antennas in a mutually aligned relation; and (d) obtaining said relative magnitude and phase at each of said positions with the respective magnetic field vectors of said antennas in a mutually aligned relation.

Claim 4

A method as set forth in claim 2 wherein each of said transmitting and receiving antennas is a loop antenna formed substantially in a loop plane, said loop antennas each having an electric field vector parallel to said loop plane and a magnetic field vector perpendicular to said loop plane, and wherein: (a) said loop antennas are positioned with the loop plane vertical and substantially coplanar to thereby align said electric field vectors; and (b) said loop antennas are positioned with said loop planes vertical, parallel, and axially aligned to thereby align said magnetic field vectors.

Claim 5

A method as set forth in claim 1 wherein said receivers are spaced a first known distance from said transmitter for obtaining a first relative phase of reflected signal components and including the steps of: (a) moving said receivers a second known distance from said transmitter; (b) obtaining a second relative phase for reflected signal components received at said second known distance; and (c) computing the depth of said subterranean formations from a formula relating said known distances to said first and second relative phases.

Claim 6

A method as set forth in claim 1 wherein: (a) each of said first and second receivers has an adjustable output level and an output level meter; and including: (b) establishing common gain characteristics for said first and second receivers by adjusting said receivers to a predetermined output level for a given signal input level at a first of said positions along said survey path; and (c) balancing said first and second receivers to the same output level during reception of said calibration signal thereby, at each of said positions.

Claim 7

A method as set forth in claim 5 including: (a) conducting a signal of known level and at said predetermined frequency into each of said first and second receivers at said first position along said survey path; and (b) adjusting each of said first and second receivers to said predetermined output level to thereby establish said common gain characteristics.

Claim 8

A method as set forth in claim 5 wherein the power output level of said transmitter is adjustable and including: (a) providing a third receiver adapted for receiving vertically polarized signal components only and having an adjustable output level and an output meter; (b) adjusting said third receiver to have said predetermined output level for said given signal input level at said first position along said survey path; and at each of said positions: (c) adjusting said transmitter power output level such that the output level of said third receiver is substantially identical to said predetermined output level; and (d) adjusting the output levels of each of said first and second receivers to said predetermined output level subsequent to said adjusting said transmitter power output level.

Claim 9

A method as set forth in claim 7 including: (a) conducting a signal of known level and at said predetermined frequency into each of said first, second, and third receivers at said first position; and (b) adjusting each of said first, second, and third receivers for said predetermined output level at said first position to thereby establish said common gain characteristics.

Claim 10

A method as set forth in claim 1 and including: (a) recording said magnitude and phase of said calibration difference signal by electronically storing said magnitude in a magnitude register and said phase in a phase register; (b) providing computer means operative to transfer said magnitude and phase of said calibration difference signal respectively from said magnitude and phase registers to memory means associated with said computer means; (c) recording said magnitude and phase of said survey difference signal by storing same respectively in said magnitude and phase registers; (d) said computer means transferring said magnitude and phase of said survey difference signal into said memory means; (e) said computer means recalling said survey difference signal magnitude and phase and recalling and vectorially subtracting said calibration difference signal magnitude and phase respectively therefrom resulting in said relative magnitude and phase for one of said positions along said survey path; (f) recording said relative magnitude and phase by said computer means storing same in said memory means; (g) said computer means storing a relative magnitude and phase similarly obtained for each of said positions in said memory means; and (h) said computer means controlling a plotter to thereby plot a relative magnitude and phase for each of said positions thereby obtaining said graph.

Claim 11

In an apparatus for radio geophysical surveying including a transmitter, transmitting antenna means, a first receiver connected to a first receiving antenna responsive to vertically polarized signal components only, and a second receiver connected to a second receiving antenna responsive to both vertically and horizontally polarized signal components, each of said transmitter, transmitting antenna means, receivers, and receiving antennas being tuned to a predetermined frequency, said receivers having respective output signals in response to operation of said transmitter, said apparatus for determining the relative magnitude and phase of horizontally polarized signal components radiated from said transmitting antenna means, propagated into the earth, reflected to the surface by subterranean formations and received by said second receiver through said second receiving antenna, said relative magnitude and phase being determined for each of a plurality of positions along a survey path, the improvement comprising: (a) a difference amplifier having one input connected to the output of said first receiver and another input connected to the output of said second receiver, said difference amplifier having a difference output signal proportional to the vectorial difference of said receiver output signals; (b) means for measuring the magnitude of said difference signal connected to the output of said difference amplifier; and (c) phase measuring means connected to the output of said difference amplifier and to the output of said first receiver for measuring the phase of said difference signal relative to the phase of the output signal of said first receiver.

Claim 12

In an apparatus for radio geophysical surveying including a transmitter, transmitting antenna means, a first receiver connected to a first receiving antenna responsive to vertically polarized signal components only, and a second receiver connected to a second receiving antenna responsive to both vertically and horizontally polarized signal components, each of said transmitter, transmitting antenna means, receivers, and receiving antennas being tuned to a predetermined frequency, said receivers having respective output signals in response to operation of said transmitter, said apparatus for determining the relative magnitude and phase of horizontally polarized signal components radiated from said transmitting antenna means, propagated into the earth, reflected to the surface by subterranean formations and received by said second receiver through said second receiving antenna, said relative magnitude and phase being determined for each of a plurality of positions along a survey path, the improvement comprising: (a) a difference amplifier having one input connected to the output of said first receiver and another input connected to the output of said second receiver, said difference amplifier having a difference output signal proportional to the vectorial difference of said receiver output signals; (b) means for measuring the magnitude of said difference signal connected to the output of said difference amplifier; and (c) phase measuring means connected to the output of said difference amplifier and to the output of said first receiver for measuring the phase of said difference signal relative to the phase of the output signal of said first receiver.

Claim 13

In an apparatus for radio geophysical surveying including a transmitter, transmitting antenna means, a first receiver connected to a first receiving antenna responsive to vertically polarized signal components only, and a second receiver connected to a second receiving antenna responsive to both vertically and horizontally polarized signal components, each of said transmitter, transmitting antenna means, receivers, and receiving antennas being tuned to a predetermined frequency, said receivers having respective output signals in response to operation of said transmitter, said apparatus for determining the relative magnitude and phase of horizontally polarized signal components radiated from said transmitting antenna means, propagated into the earth, reflected to the surface by subterranean formations and received by said second receiver through said second receiving antenna, said relative magnitude and phase being determined for each of a plurality of positions along a survey path, the improvement comprising: (a) a difference amplifier having one input connected to the output of said first receiver and another input connected to the output of said second receiver, said difference amplifier having a difference output signal proportional to the vectorial difference of said receiver output signals; (b) means for measuring the magnitude of said difference signal connected to the output of said difference amplifier; (c) phase measuring means connected to the output of said difference amplifier and to the output of said first receiver for measuring the phase of said difference signal relative to the phase of the output signal of said first receiver; (d) a magnitude storage register connected to said magnitude measuring means for storing the magnitude of said difference signal; (e) a phase storage register connected to said phase measuring means for storing the phase of said difference signal; (f) computer means having said magnitude register and said phase register connected thereto and including: (1) memory means for receiving two successive values, each of said values including the magnitude and the phase for each of said positions along said survey path; and (2) means for complex subtraction of a first of said successive values of said magnitude and phase from the second of said successive values for each of said positions, thereby obtaining a resultant magnitude and phase for each of said positions in said memory means; and (g) plotting means connected to said computer means for plotting said resultant magnitude and phase for each of said positions along said survey path.

Claim 14

In an apparatus for radio geophysical surveying including a transmitter, transmitting antenna means, a first receiver connected to a first receiving antenna responsive to vertically polarized signal components only, and a second receiver connected to a second receiving antenna responsive to both vertically and horizontally polarized signal components, each of said transmitter, transmitting antenna means, receivers, and receiving antennas being tuned to a predetermined frequency, said receivers having respective output signals in response to operation of said transmitter, said apparatus for determining the relative magnitude and phase of horizontally polarized signal components radiated from said transmitting antenna means, propagated into the earth, reflected to the surface by subterranean formations and received by said second receiver through said second receiving antenna, said relative magnitude and phase being determined for each of a plurality of positions along a survey path, the improvement comprising: (a) a difference amplifier having one input connected to the output of said first receiver and another input connected to the output of said second receiver, said difference amplifier having a difference output signal proportional to the vectorial difference of said receiver output signals; (b) means for measuring the magnitude of said difference signal connected to the output of said difference amplifier; (c) phase measuring means connected to the output of said difference amplifier and to the output of said first receiver for measuring the phase of said difference signal relative to the phase of the output signal of said first receiver; (d) a magnitude storage register connected to said magnitude measuring means for storing the magnitude of said difference signal; (e) a phase storage register connected to said phase measuring means for storing the phase of said difference signal; (f) computer means having said magnitude register and said phase register connected thereto and including: (1) memory means for receiving two successive values, each of said values including the magnitude and the phase for each of said positions along said survey path; and (2) means for complex subtraction of a first of said successive values of said magnitude and phase from the second of said successive values for each of said positions, thereby obtaining a resultant magnitude and phase for each of said positions in said memory means; and (g) plotting means connected to said computer means for plotting said resultant magnitude and phase for each of said positions along said survey path.

Claim 15

In an apparatus for radio geophysical surveying including a transmitter, transmitting antenna means, a first receiver connected to a first receiving antenna responsive to vertically polarized signal components only, and a second receiver connected to a second receiving antenna responsive to both vertically and horizontally polarized signal components, each of said transmitter, transmitting antenna means, receivers, and receiving antennas being tuned to a predetermined frequency, said receivers having respective output signals in response to operation of said transmitter, said apparatus for determining the relative magnitude and phase of horizontally polarized signal components radiated from said transmitting antenna means, propagated into the earth, reflected to the surface by subterranean formations and received by said second receiver through said second receiving antenna, said relative magnitude and phase being determined for each of a plurality of positions along a survey path, the improvement comprising: (a) a difference amplifier having one input connected to the output of said first receiver and another input connected to the output of said second receiver, said difference amplifier having a difference output signal proportional to the vectorial difference of said receiver output signals; (b) means for measuring the magnitude of said difference signal connected to the output of said difference amplifier; (c) phase measuring means connected to the output of said difference amplifier and to the output of said first receiver for measuring the phase of said difference signal relative to the phase of the output signal of said first receiver; (d) each of said first and second receivers having an adjustable output level and an output level meter; (e) a third receiver connected to said first receiving antenna, said third receiver having an adjustable output level and an output level meter; (f) said third receiver being adjusted at the first of said positions along said survey path to a predetermined output level thereof for a given input level thereinto; and (g) said first and second receivers each being adjusted for said predetermined output level during reception of a signal containing said vertically polarized signal components only, at each of said positions.

Claim 16

In an apparatus for radio geophysical surveying including a transmitter, transmitting antenna means, a first receiver connected to a first receiving antenna responsive to vertically polarized signal components only, and a second receiver connected to a second receiving antenna responsive to both vertically and horizontally polarized signal components, each of said transmitter, transmitting antenna means, receivers, and receiving antennas being tuned to a predetermined frequency, said receivers having respective output signals in response to operation of said transmitter, said apparatus for determining the relative magnitude and phase of horizontally polarized signal components radiated from said transmitting antenna means, propagated into the earth, reflected to the surface by subterranean formations and received by said second receiver through said second receiving antenna, said relative magnitude and phase being determined for each of a plurality of positions along a survey path, the improvement comprising: (a) a difference amplifier having one input connected to the output of said first receiver and another input connected to the output of said second receiver, said difference amplifier having a difference output signal proportional to the vectorial difference of said receiver output signals; (b) means for measuring the magnitude of said difference signal connected to the output of said difference amplifier; (c) phase measuring means connected to the output of said difference amplifier and to the output of said first receiver for measuring the phase of said difference signal relative to the phase of the output signal of said first receiver; (d) each of said first and second receivers having an adjustable output level and an output level meter; (e) a third receiver connected to said first receiving antenna, said third receiver having an adjustable output level and an output level meter; (f) said third receiver being adjusted at the first of said positions along said survey path to a predetermined output level thereof for a given input level thereinto; and (g) said first and second receivers each being adjusted for said predetermined output level during reception of a signal containing said vertically polarized signal components only, at each of said positions.

Claim 17

An apparatus as set forth in claim 12 including: a calibration unit connected to each of said receivers at the first of said plurality of positions along said survey path, said calibration unit generating a signal of known level and frequency for establishing said predetermined output level.

Claim 18

An apparatus as set forth in claim 12 including: (a) a single local oscillator for converting the frequency of the signals received by said receivers to a lower frequency, said local oscillator having a plurality of identical outputs; (b) one of said identical outputs being connected to said first receivers; (c) a second of said identical outputs being connected to said second receiver; and (d) a third of said identical outputs being connected to said third receiver.

Claim 19

In an apparatus for radio geophysical surveying including a transmitter, transmitting antenna means, a first receiver connected to a first receiving antenna responsive to vertically polarized signal components only, and a second receiver connected to a second receiving antenna responsive to both vertically and horizontally polarized signal components, each of said transmitter, transmitting antenna means, receivers, and receiving antennas being tuned to a predetermined frequency, said receivers having respsective output signals in response to operation of said transmitter, said apparatus for determining the relative magnitude and phase of horizontally polarized signal components radiated from said transmitting antenna means, propagated into the earth, reflected to the surface by subterranean formations and received by said second receiver through said second receiving antenna, said relative magnitude and phase being determined for each of a plurality of positions along a survey path, the improvement comprising: (a) a difference amplifier having one input connected to the output of said first receiver and another input connected to the output of said second receiver, said difference amplifier having a difference output signal proportional to the vectorial difference of said receiver output signals; (b) means for measuring the magnitude of said difference signal connected to the output of said difference amplifier; (c) phase measuring means connected to the output of said difference amplifier and to the output of said first receiver for measuring the phase of said difference signal relative to the phase of the output signal of said first receiver; and (d) said transmitter including: (1) oscillator means providing an oscillator signal, (2) a controlled transconductance amplifier connected to said oscillator means and having a gain control input, the gain of said controlled transconductance amplifier being determined by the level of an error signal applied at said gain control input, (3) an RF amplifier connected to an output of said controlled transconductance amplifier, (4) level sensing means connected to an output of said RF amplifier, said level sensing means generating an error signal proportional to the output level of said RF amplifier, and (5) said error signal being communicated to said controlled transconductance amplifier gain control input to control the gain thereof, said level sensing means and said controlled transconductance amplifier being operative to maintain a preset power output level of said transmitter.

Claim 20

In an apparatus for radio geophysical surveying including a transmitter, transmitting antenna means, a first receiver connected to a first receiving antenna responsive to vertically polarized signal components only, and a second receiver connected to a second receiving antenna responsive to both vertically and horizontally polarized signal components, each of said transmitter, transmitting antenna means, receivers, and receiving antennas being tuned to a predetermined frequency, said receivers having respsective output signals in response to operation of said transmitter, said apparatus for determining the relative magnitude and phase of horizontally polarized signal components radiated from said transmitting antenna means, propagated into the earth, reflected to the surface by subterranean formations and received by said second receiver through said second receiving antenna, said relative magnitude and phase being determined for each of a plurality of positions along a survey path, the improvement comprising: (a) a difference amplifier having one input connected to the output of said first receiver and another input connected to the output of said second receiver, said difference amplifier having a difference output signal proportional to the vectorial difference of said receiver output signals; (b) means for measuring the magnitude of said difference signal connected to the output of said difference amplifier; (c) phase measuring means connected to the output of said difference amplifier and to the output of said first receiver for measuring the phase of said difference signal relative to the phase of the output signal of said first receiver; and (d) said transmitter including: (1) oscillator means providing an oscillator signal, (2) a controlled transconductance amplifier connected to said oscillator means and having a gain control input, the gain of said controlled transconductance amplifier being determined by the level of an error signal applied at said gain control input, (3) an RF amplifier connected to an output of said controlled transconductance amplifier, (4) level sensing means connected to an output of said RF amplifier, said level sensing means generating an error signal proportional to the output level of said RF amplifier, and (5) said error signal being communicated to said controlled transconductance amplifier gain control input to control the gain thereof, said level sensing means and said controlled transconductance amplifier being operative to maintain a preset power output level of said transmitter.

Claim 21

An apparatus as set forth in claim 15 including: a reference potentiometer connected to said level sensing means, said potentiometer being selectively adjustable to preset said power output level of said transmitter.

Claim 22

An apparatus as set forth in claim 15 including: (a) a plurality of reference potentiometers, each potentiometer being selectively adjustable to preset a power output level of said transmitter; and (b) switch means connected to said level sensing means and having each of said reference potentiometers connected thereto, said switch means being selectively operable to connect one of said reference potentiometers to said level sensing means to thereby preset a power output level of said transmitter.

Claim 23

An apparatus as set forth in claim 17 wherein said transmitter includes an RF power amplifier connected to said RF amplifier and has a plurality of transmitting antennas associated therewith and wherein: (a) said switch means includes antenna switch means connected to said RF power amplifier and to each of said plurality of transmitting antennas; and (b) operation of said switch means effects connection of one of said transmitting antennas to said RF power amplifier in addition to selection of a reference potentiometer associated with said one transmitting antenna.

Claim 24

An apparatus as set forth in claim 18 including: antenna changeover sequencer means connected to said switch means and to said controlled transconductance amplifier; said sequencer means being operative to decrease the power output level of said transmitter to a low level during operation of said switch means for protection of said antenna switch means.