Swept range gate radar system for detection of nearby objects

• US 5,896,102 A
• Filed: 07/28/1997
• Issued: 04/20/1999
• Est. Priority Date: 09/02/1994
• Status: Expired due to Fees

• Current Assignee: Zircon Corporation
• Original Assignee: Zircon Corporation
• Inventors: Heger, Charles E.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US08/901,116
• Time in Patent Office: 631 Days
• Field of Search: 342/21, 342/22, 342/85, 342/94, 342/136, 342/137, 342/95, 367/88, 367/95, 367/98, 367/101, 367/105, 367/908, 324/329
• US Class Current: 342/85
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/103 particularities of the measurement of the distance G01S13/12, G01S13/14, G01S13/16, G01S13/18 and G01S13/20 take precedence
• CPC Class Codes: G01S 13/18 wherein range gates are used
• CPC Class Codes: G01S 13/88 Radar or analogous systems specially adapted for specific applications electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 7/03 Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
• CPC Class Codes: G01S 7/282 Transmitters
• CPC Class Codes: G01S 7/285 Receivers
• CPC Class Codes: G01S 7/34 Gain of receiver varied automatically during pulse-recurrence period, e.g. anti-clutter gain control
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

A cost-effective ultra-wideband radar system capable of locating nearby buried objects such as reinforcing steel rods, pipes, and other objects buried in concrete, soil, behind walls, or in the air. A sequence of ultra-wideband radar pulses e.g. at a plurality of frequencies in a range of about 2 MHz to about 10 GHz are emitted without a carrier and the system detects deflected pulse energy caused by the transmitted pulse whenever encountering a change in the medium i.e. an air to metal change or concrete to metal change. This reflected energy is detected and visually displayed. The range gate delay of the receiver is continuously varied, thus changing the distance from the unit to where the reflected energy would be potentially detected from the target. By continuously sweeping the "depth" of the scan, the operator need only move the unit in two dimensions across the surface to detect objects buried or hidden at varying depths interior to or behind the surface. The range gate system includes a multipoint background subtraction, corrected gain with distance, linear range gate time correction and a dielectric constant correction for a calibrated distance display.

Claims

1. A range swept radar system adapted for sensing a nearby target, comprising:

a signal transmitter;

a receiver located for receiving the signals emitted by the transmitter after being reflected from the target;

a variable delay for sweeping a selected one of the emitted and received signals;

means for stepping the variable delay in predetermined increments;

means for determining at each increment a received amount of a clutter background signal not reflected from the target;

means for storing the determined amount of the background signal for each increment; and

means for subsequently correcting a received signal at a particulars variable delay by the stored amount.

2. A transmitter range swept radar system adapted for sensing a nearby target comprising:

a signal transmitter driven by a continuously variable time delay circuit; and

a receiver driven by a fixed time delay circuit and located for receiving the signals transmitted by the transmitter after being reflected from the nearby target;

wherein a range gate time of the transmitter is variable and a range gate time of the receiver is fixed.

3. The system of claim 2, further comprising:

means for stepping the variable time delay in a variable delay for sweeping a selected one of the emitted and received signals;

means for stepping the variable delay in predetermined increments;

means for determining at each increment a received amount of a random, reflected energy background signal which is clutter not from the target;

means for storing the determined amount of the background signal for each increment; and

means for subsequently correcting a received signal at a particular variable delay by the stored amount.

4. A range swept radar system adapted for sensing a nearby target comprising:

a signal transmitter driven by a continuously variable delay circuit;

a receiver located for receiving the signals transmitted by the transmitter after being reflected from the nearby target;

means for stepping the variable delay in predetermined increments;

means for determining at each increment a received amount of a random, reflected energy background signal which is clutter not from the target;

means for storing the determined amount of the background signal for each increment; and

means for subsequently correcting a received signal at a particular variable delay by the stored amount.