Ground-penetrating imaging and detecting radar

• US 6,522,285 B2
• Filed: 03/28/2001
• Issued: 02/18/2003
• Est. Priority Date: 06/27/2000
• Status: Active Grant

• Current Assignee: Gerald L. Stolarczyk, Larry G. Stolarczyk
• Original Assignee: Gerald L. Stolarczyk, Larry G. Stolarczyk
• Inventors: Stolarczyk, Larry G., Stolarczyk, Gerald L.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US09/820,498
• Publication Number:
  US 20020011947A1
• Time in Patent Office: 692 Days
• Field of Search: 342/21, 342/22, 342/27, 342/28, 342/82, 342/89, 342/118, 342/175, 342/189-197, 342/124-146
• US Class Current: 342/22
• CPC Class Codes: F41H 11/12 Means for clearing land minefields; Systems specially adapted for detection of landmines
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

A ground-penetrating radar comprises a single resonant microstrip patch antenna (RMPA) that is driven by a three-port directional coupler. A reflected-wave output port is buffered by a wideband isolation amplifier and a reflected-wave sample is analyzed to extract measured values of the real and imaginary parts of the load impedance-the driving point impedance of RMPA. Each such port will vary in a predictable way according to how deeply an object is buried in the soil. Calibration tables can be empirically derived. Reflections also occur at the interfaces of homogeneous layers of material in the soil. The reflected-wave signals are prevented from adversely affecting transmitted-signal sampling by putting another wideband isolation amplifier in front of the input port of the directional coupler. A suppressed-carrier version of the transmitted signal is mixed with the reflected-wave sample, and the carrier is removed. Several stages of filtering result in a DC output that corresponds to the values of the real and imaginary parts of the load impedance. The suppressed-carrier version of the transmitted signal is phase shifted 0° or 90° to select which part is to be measured at any one instant.

Claims

1. A close-proximity radar system, comprising:

a sensor antenna for transmitting a radio signal and for receiving any reflected signals, and having a driving point impedance that depends on dimensional and dielectric constant characteristics of any objects proximately disposed in a material media and any radio reflected-wave signals returned by them;

a first directional coupler connected by its output port to the sensor antenna, and having a reverse port providing for samples of said reflected signals, and also having an input port;

a second directional coupler operating as a power splitter and having an input port connected to a radio frequency oscillator, a forward output port providing for samples of signals from said radio frequency oscillator, and another output port;

a wideband isolation amplifier connected between said output port of the second directional coupler and said input port of the first directional coupler, and providing an isolation of said samples of signals from said radio frequency oscillator from said reflected signals; and

a demodulator including a plurality of mixers connected to demodulate said reflected signals with said samples of signals from said radio frequency oscillator, and for providing an output signal related to at least one of a reactive and resistive component of said antenna driving point impedance and said any reflected-wave signals.

2. The system of claim 1, further comprising:

an interpreter for converting said output signal from the demodulator into at least one of a distance estimate of said objects from the sensor antenna, a dielectric constant estimate of said material medias, a thickness estimate of said material medias, a size estimate of any of said objects disposed in said material medias, and a stress estimate of any stresses existing in said material medias.

3. The system of claim 1, further comprising:

a mixer included in the demodulator and providing for removal of a carrier frequency from said reflected-wave signals with said samples of signals from said radio frequency oscillator, and for producing a suppressed-carrier double-sideband output.

4. The system of claim 1, wherein:

the electrical power is generated by a water turbine.

5. The system of claim 1, wherein:

the antenna I and Q impedance values are transmitted by radiowaves to remote computer for processing.

6. The system of claim 5, wherein:

other measurement data such as pick block side and drag force value are measured and transmitted by radiowaves to computer for processing.

7. The system of claim 1, wherein:

an impedance spiral function is used in data processing to determine the specific characteristics.

8. The system of claim 7, wherein:

an inclinometer on the cutting boom relates the impedance spiral to uncut thickness.

9. The system of claim 1, wherein:

a radar distance and dielectric product is determined by fast Fourier transform processing of radar data simultaneous to a determination of the dielectric constant from an independent measurement.

10. The system of claim 1, wherein:

the RMPA has a mechanical means to adjust the driving point impedance to match a characteristic impedance of the feed.

11. A ground-penetrating radar system, comprising:

a reference oscillator providing for a reference-frequency signal (FX);

a first phase-locked loop (PLL1) connected to convert said reference-frequency signal into a first frequency (F1) signal;

a second phase-locked loop (PLL2) connected to convert said reference-frequency signal into a first frequency (F2) signal;

a third phase-locked loop (PLL0) connected to convert said reference-frequency signal into the first transmitter frequency (FO);

at least one of a resonant microstrip patch antenna (RMPA) and microwave antenna that provide a feed;

a first three-port directional coupler with an input port, an output port connected to the feed, and a reflected-sample port;

a first wideband isolation amplifier connected between the transmitter (PLL0) and said input port of the first three-port directional coupler;

a second wideband isolation amplifier connected between reflected-sample port of the first three-port directional coupler and the first mixer; and

a driving-point impedance measurement device.

12. The system of claim 11, wherein:

the PLL1 further provides said F1 signal in fixed harmonic frequencies of said reference-frequency signal.

13. The system of claim 11, wherein:

the PLL2 further provides said F2 signal in fixed harmonic frequencies of said reference-frequency signal.

14. The system of claim 11 wherein:

the PLL0 further provides an FO signal that can be manipulated to a particular harmonic of said reference frequency signal.

15. The system of claim 11, wherein:

the first mixer output is bandpass filtered and comprises a single-frequency term with an amplitude related to a magnitude, and a phase angle related to at least one of an antenna sensor phase angle driving point impedance or the reflection coefficient of the antenna feed.

16. The system of claim 11, wherein:

the output signal of the final mixer is after filtering, a DC term which is proportional to the magnitude and phase angle of the reflection coefficient of the feed.

17. The system of claim 11, wherein:

the phase shift of 90°

causes a second DC term, the ratio of which is the cotangent of the phase of the reflection coefficient.

18. The system of claim 11, wherein:

the phase value is used to solve for the magnitude of the reflection coefficient.