Broadband electromagnetic field component measurement system

• US 6,564,158 B1
• Filed: 08/17/2000
• Issued: 05/13/2003
• Est. Priority Date: 08/17/2000
• Status: Active Grant

• Current Assignee: Rantec Holdings, Inc. (Walker Innovation Inc. (f/k/a Patent Properties, Inc.))
• Original Assignee: Holaday Industries, Inc. (ESCO Technologies, Inc.)
• Inventors: Rabel, Jay A., Stadler, Steven R.
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): TSAI, CAROL S W
• Application Number:
  US09/640,574
• Time in Patent Office: 999 Days
• Field of Search: 702/38, 702/57, 702/64-66, 702/85, 702/86, 702/91, 702/104, 702/105, 702/107, 702/108, 702/109, 702/115, 702/124, 702/92, 702/122, 702/126, 702/93, 702/183, 702/188, 702/189, 702/FOR-103, 702/FOR.106, 702/FOR.110, 702/FOR.134, 702/FOR-156, 702/FOR.165, 702/FOR-170, 702/FOR.173, 324/202, 324/225, 324/224-247, 324/207.11, 333/55.R, 333/56, 333/57
• US Class Current: 702/57
• CPC Class Codes: G01R 29/0892 Details related to signal analysis or treatment; presenting results, e.g. displays; measuring specific signal features other than field strength, e.g. polarisation, field modes, phase, envelope, maximum value

Abstract

Apparatus and method having a probe and readout for taking electromagnetic field measurements by acquiring raw data and linearizing the data either during processing or after processing by using a curve-fitting equation to non-linearly interpolate between calibration data points. A curve-fitting equation of the form V/m=a+bx^c is used for selected segments of the data and the invention requires only the retention of numerical values for the coefficients a, b, and c for each data segment. The coefficient values are stored in the probe and used either by the probe or the readout to construct calibrated data in volts per meter (V/m).

Claims

1. A method of acquiring calibrated electromagnetic field data using a probe and readout comprising the steps of:

a. acquiring electromagnetic field data using a multiple axis sensing probe;

b. transmitting the field data in an uncalibrated form from the probe to a readout;

c. calibrating the field data using a non-linear interpolation and linearization function by inserting predetermined values for coefficients into a curve-fitting equation previously used to calibrate a plurality of data points using a known field applied to the sensing probe; and

d. presenting the calibrated field data to a user using the readout,

wherein the field data is volts per meter (V/m) and the curve-fitting equation is of the form V/m=a+bx^c where a, b, and c are the coefficients determined to linearize an uncalibrated data point “

x”

to provide calibrated volts per meter data.

2. The method of claim 1 wherein step c. further comprises using a plurality of sets of numerical values for the coefficients, where each set of numerical values corresponds to a separate segment using the curve-fitting equation.

3. The method of claim 1 wherein a separate set of numerical values for of the a, b, and c coefficients are used for each of a plurality of segments using the curve-fitting equation.

4. The method of claim 1 wherein the readout comprises a personal computer using Active X software technology to calibrate the data.

5. The method of claim 1 wherein the readout comprises a virtual readout using software on a personal computer.

6. The method of claim 1 wherein the readout comprises a rack mounted display.

7. The method of claim 1 wherein the readout comprises a hand held display.

8. The method of claim 1 wherein step c. further comprises preparing a look-up table of calibrated field data corresponding to every possible value of uncalibrated field data capable of being sent from the probe to the readout.

9. The method of claim 1 wherein the field data of step b further comprises a gain setting level and an analog to digital converter output reading.

13. The method of claim 1 wherein step c is performed on each individual data point as it is received by the readout.

14. The method of claim 1 wherein step c is performed after a plurality of data points are received by the readout.

10. The method of claim wherein the non-linear interpolation and linearization function comprises performing a segmented least squares curve fit to a predetermined equation.

11. The method of claim 10 wherein the predetermined equation comprises an expression of the form a+bx^c, where a, b, and c are the coefficients and x is an uncalibrated field data point.

12. The method of claim 11 wherein the least squares curve fit further comprises performing a Levenberg-Marquardt error minimization curve-fitting procedure.