Portable geophysical system using an inverse collocation-type metehodology

• US 5,644,314 A
• Filed: 03/29/1996
• Issued: 07/01/1997
• Est. Priority Date: 03/29/1996
• Status: Expired due to Fees

• Current Assignee: Army Corps of Engineers
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Evans, James A., Ahmad, Falih H.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/625,080
• Time in Patent Office: 459 Days
• Field of Search: 342/22, 342/192, 342/196, 342/197
• US Class Current: 342/22
• CPC Class Codes: G01S 13/325 using transmission of coded signals, e.g. P.S.K. signals
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 7/412 based on a comparison between measured values and known or stored values
• CPC Class Codes: G01V 3/17 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

The invention pertains to a hand-held or vehicle mountable portable procer based high resolution radar system for detecting and identifying an object by using high resolution radar. In particular, the invention concerns using radio waves for identifying a depth and material of an object within a media. This system can perform target and media identification in real-time. This process is achieved by the system'"'"'s processor where the media identification results can be visually displayed on an output unit. The generated carrier signal used in the radar system is an exponentially decaying superimposed direct and alternating signal. The frequency of the carrier signal can be in the microwave region. The system performs analog to digital (A/D) conversion using integrated circuitry whose sampling rate is in the same as the carrier signal transmission rate. In addition, Fourier and Hilbert transforms of the observed signal is generated for frequency domain analysis of the observed object to be identified and a profile inversion methodology for real time analysis. To achieve high resolution results, digital codes such as Barker, Welti, or Frank codes are used in the processor. The carrier signal is coded using a digitally controlled phase shifter. Power usage by the instant invention'"'"'s radar system is low. The profile inversion methodology is a real time based analysis.

Claims

1. A portable processor based system for detecting an object with a transmitting/receiving signal means for transmitting an electromagnetic wave and receiving as an observation signal a reflected wave which is an electromagnetic wave returned from the object with input means and output display means comprising:

the transmitting signal means including;

a means for producing a pulse repetition frequency carrier signal that includes an oscillator thereby producing a stable output signal that is a square wave;

a means for producing a carrier generating signal that includes a circuit with under-damped oscillator with narrow band filtering capability thereby producing an exponentially decaying dc signal along with a superimposed exponentially decaying sinusoidal carrier signal, the carrier generating signal is gated ON only during transmission of a desired code thereby minimizing system power usage;

a means for producing a phase shifting of the a modulated carrier signal with the desired code that is a digitally controlled phase shift keying modulator unit;

a means for amplifying the transmitted modulated carrier signal towards the observed objects through a narrow beam-width antenna;

the receiving signal means including;

a narrow beam-width antenna;

a means for observation signal envelope detection which includes a positive-intrinsic-negative diode for detecting this envelope along with a means for cross-correlating the envelope of the observation signal with the desired code used thereby producing a high-resolution time compressed version of the observation signal envelope that generates a base band signal characteristic of the object observed for output display by the by the output means;

a means for generating an input signal to a means for performing a collocation-type inversion method from the observation signal which is first digitized at multiples of the carrier signal'"'"'s rate using an analog to digital (A/D) convertor;

a means for performing real-time inversion and generation of desired electromagnetic profiles that includes the processor for implementing the collocation-type inversion method wherein the input signal is inputted into the means for performing the inversion method that;

i) generates polynomials and its'"'"' derivatives from the input signal;

if) generates a set of algebraic equations with unknowns being the desired profiles; and

iii) solves the set of algebraic equations for the unknowns which produces the desired electromagnetic profiles of the object being observed;

a means for frequency domain analysis of the A/D signals generated using a Fourier and Hilbert transform unit for material classification of the object; and

the display means outputs electromagnetic profiles of the object observed of the objects permittivity, conductivity, permeability and susceptibility.

2. The system of claim 1 wherein the means for performing inversion and generation of desired electromagnetic profiles using the collocation-type inversion method uses an impulse response signal as the input signal for is inputting to the inversion method that sequentially:

i) generates polynomials and its'"'"' derivatives from the impulse response signal for constructing an approximate susceptibility profile defined by Legendre-Gauss-Labatto points as collocation points and Lagrange polynomials as trial functions;

ii) generates a set of algebraic equations with unknowns being the desired susceptibility profile; and

iii) solves these set of algebraic equations for their unknowns which produces the desired susceptibility profile of the object being observed for display by the output means.

3. The system of claim 1 wherein the desired code is Barker code.

4. The system of claim 1 wherein the desired code is Welti code.

5. The system of claim 1 wherein the desired code is Frank code.

6. The system of claim 1 wherein the desired code is Costas code.