GEOPHYSICAL SURVEYING SYSTEM EMPLOYING ELECTROMAGNETIC IMPULSES

• US 3,806,795 A
• Filed: 01/03/1972
• Issued: 04/23/1974
• Est. Priority Date: 01/03/1972
• Status: Expired due to Term

• Current Assignee: Rexford M. Morey
• Original Assignee: Rexford M. Morey
• Inventors: Morey, Rexford M.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US05/214,933
• Time in Patent Office: 841 Days
• Field of Search: 324/3,4,6,52,740 343/5,11,13
• US Class Current: 324/337
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005
• CPC Class Codes: H01Q 9/005 for radiating non-sinusoidal waves

Abstract

A geophysical survey system is disclosed for determining the character of the subterrain by analysis of reflections from electromagnetic pulses radiated into the ground. The system repetitively radiates into the ground a short duration electromagnetic pulse having a rise time in the order of 1 nanosecond. The antenna which radiates the pulse into the ground is employed to receive the reflections of the pulse. The received signals are coupled through a transmit-receive network to a receiver which permits the input signal waveform to be reconstructed from a sequence of samples taken by the receiver. The system is capable of generating a profile chart indicating the magnitudes of the reflected signals and the depths at which the reflections occurred.

Claims

1. A geophysical surveying system for ascertaining the character of the subterrain at shallow depths, the system comprising a pulse generator for repetitively generating a unipolar electromagnetic pulse having a rise time in the order of 1 nanosecond and a duration of 10 nanoseconds or less, an antenna for transmitting the unipolar pulse into the terrain and for receiving echos of the transmitted pulse, the antenna having elongate radiators that are fan shaped for at least a portion of their length, the apexes of the fans being adjacent to one another, the signal connections to the antenna being at the apexes of the fans, and the ends of tHe radiators remote from the apexes being terminated by wave energy absorbing means which inhibit ringing of the antenna by the transmitted pulse whereby echos from the energy propagated into the terrain are not masked to any appreciable extent by ringing of the antenna, a receiver having signal sampling means permitting an input signal to be reconstructed from the samples, and transmit-receive means coupling the antenna to the pulse generator and to the signal receiver.

2. In a geophysical surveying system of the type having a pulse generator which repetitively supplies pulses to an antenna that radiates electromagnetic energy into the terrain to enable the character of the subterrain at shallow depths to be ascertained from reflections of the radiated electromagnetic energy, the improvement wherein the pulse generator is adapted to repetitively generate a unipolar electromagnetic pulse having a rise time of less than 2 nanoseconds and a duration of 10 nanoseconds or less, and the antenna has elongate radiators that are fan shaped for at least a portion of their length, the apexes of the fans being adjacent to one another, the pulse from the generator being coupled to the radiators at the apexes of the fans, and the ends of the radiators remote from the apexes being terminated by energy absorbers which inhibit ringing of the antenna by absorbing pulse energy reaching the ends of the radiators.