Underground object locating system without direction ambiguity
AssigneeGeometrics, Inc.
InventorKenneth R. Smith
Life of this patent
Estimating the term…
Abstract
In an underground object locating system in which a modulated RF signal is applied to the underground object and an emitted signal is detected by a receiver, ambiguity in the direction of current flow in the underground object is resolved by modulating the RF signal with a modulation signal such that the modulated signal, f(t) has an average value of zero and is not equal to −f(t+K) where K is any practical value. In specific embodiments, the modulation can be amplitude modulation where the modulating signal is lower in frequency than the RF signal and is related thereto by a rational number, such as one-half (½).
Claims19
In a system for locating underground objects by the reception of radio waves created by current flow through the underground object, a method of removing ambiguity of direction of current flow in the object comprising the steps of:
- a) creating an RF signal, f(t), having an average value of zero and such that
- f(t)≠f(t+K)
- for all practical values of K,
- b) applying the RF signal to the underground object to cause a current to flow through the underground object,
- c) detecting radio waves emitted from the object, and
- d) decoding the radio waves to ascertain direction of current flow through the object.
In a system for locating underground objects by the reception of radio waves emitted by the underground object, a method of removing ambiguity of direction of current flow in the object comprising the steps of:
- a) providing an RF signal, V0,
- b) modulating the RF signal by a modulation signal, V1, such that a modulated signal, f(t) has an average value of zero and is not equal to −f(t+K) where K is any value,
- c) applying the modulated signal to the underground object to cause a current to flow in the underground object,
- d) detecting radio waves emitted from the object, and
- e) decoding the radio waves to determine direction of current flow through the underground object.
A system for locating underground objects by the reception of radio waves emitted by the underground object comprising:
- a) a transmitter for applying to the underground object an RF signal, V0, and including a modulator for modulating the RF signal by a modulation signal, V1, such that the modulated RF signal, f(t) has an average value of zero and is not equal to −f(t+K) where K is any practical value,
- b) a coupler for coupling the modulated RF signal to the underground object,
- c) a receiver for receiving the modulated RF signal as emitted from the underground object,
- d) a demodulator for recovering the modulation signal, V1, and
- e) a phase detector for detecting the phase of the received RF signal relative to the phase of the modulation signal.
Dependencies are inferred from the claim text.