Patent ID: 6140819
Filing Date: 2000-10-31
Classification: G01V

Abstract:
A locator for the continuous measurement of the depths of underground objects from the surface, comprising:an antenna array that can be positioned at a point near a surface overlying an underground object that is radiating an electromagnetic wave;a top and a bottom antenna included in the antenna array and having a known separation distance between them, and respectively providing for a first and a second received alternating current (AC) electrical signal that are each representative of a first field strength and a second field strength of said electromagnetic wave at corresponding points in space;a phase-locked loop (PLL) for synthesizing a local oscillator frequency from either said first or second received AC electrical signal, wherein a gating signal is produced that is synchronized to a harmonic frequency of said first or second received AC electrical signal;a first network for connecting said first received AC electrical signal to produce a first inverted and a first non-inverted AC signal representative of said electromagnetic wave at said top antenna;a second network for connecting said second received AC electrical signal to produce a second inverted and a second non-inverted AC signal representative of said electromagnetic wave at said bottom antenna;a first analog signal switch connected to said gating signal and providing for alternatively switching between said first inverted and said first non-inverted AC signals to produce a first full-wave rectified direct current (DC) signal;a second analog signal switch connected to said gating signal and providing for alternatively switching between said second inverted and said second non-inverted AC signals to produce a second full-wave rectified DC signal in parallel with and independent from said first full-wave rectified direct current (DC) signal; anda computer providing for a continuous and real-time estimate of said depth of said underground object to a user by equating a first field strength associated with said top antenna to an electrical magnitude of said first full-wave rectified DC signal, and equating a second field strength associated with said bottom antenna to an electrical magnitude of said second full-wave rectified DC signal, wherein a continuous real-time comparison is made between said first field strength to said second field strength to estimate a depth of said underground object from which said electromagnetic wave is radiating.