Method and apparatus for high-speed scanning of electromagnetic emission levels

• US 6,268,738 B1
• Filed: 05/06/1998
• Issued: 07/31/2001
• Est. Priority Date: 11/07/1995
• Status: Expired due to Term

• Current Assignee: Ether Capital Corporation
• Original Assignee: EMSCAN Corporation
• Inventors: James, Don E., Gunthorpe, Gary E.
• Primary Examiner(s): Nguyen, Vinh P.
• Application Number:
  US09/000,231
• Time in Patent Office: 1,182 Days
• Field of Search: 324/95, 324/750, 324/501, 324/537, 324/538, 324/639, 702/85, 702/75, 702/76
• US Class Current: 324/750.02
• CPC Class Codes: G01R 31/002 where the device under test is an electronic circuit

Abstract

A method and apparatus for high-speed scanning of electromagnetic emission levels includes a synchronizer for synchronizing scanning of a device under test with digitizing a output video signal from a spectrum analyzer. The synchronizer can be responsive to a synchronization signal from the device under test or can generate a synchronization signal to the device under test. Methods for calibrating the level and frequency of the video output signal are provided. Once calibrated the high-speed scanning can be used to develop single probe multifrequency/time scans yielding amplitude versus frequency and time plots, and single frequency multiple probe/time scans yielding amplitude versus space and time plots.

Claims

1. A method for high-speed scanning of electromagnetic field levels associated with a test subject, comprising the steps of:

for each of a plurality of spatially distinct test positions on the test subject;

(a) scanning an electromagnetic probe through a test frequency range to obtain a spectral scan representing electromagnetic field levels measured adjacent to the test position;

(b) identifying one or more peak values associated with the spectral scan;

(c) calculating a calibration curve fitting the peak values;

(d) applying the calibration curve to the spectral scan to create a calibrated spectral scan; and

displaying the calibrated spectral scans for the plurality of test positions to create a spectral-spatial scan for the test subject.

2. The method of claim 1, wherein step (a) comprises scanning through the test frequency range multiple times.

3. The method of claim 1, wherein step (b) comprises the steps of:

identifying one or more peak regions in the spectral scan; and

for each peak region,

selecting a first frequency window associated with the peak region, the first frequency window defining a subset of the of the test frequency range,

obtaining a first window scan by scanning through the first frequency window, and

identifying the peak value from the first window scan.

4. The method of claim 3, wherein the step of identifying the peak value from the first window scan comprises the steps of:

identifying a second peak region within the first window scan, the second peak region defining a subset of the first peak region;

selecting a second frequency window associated with the second peak region, the second frequency window comprising a subset of the first frequency window;

obtaining a second window scan by scanning through the second frequency window; and

identifying the peak value from the second window scan.

5. The method of claim 4, wherein the step of identifying the peak value from the second window scan comprises the steps of:

identifying a third peak region within the second window scan, the third peak region defining a subset of the second peak region;

selecting a third frequency window associated with the third peak region, the third frequency window comprising a subset of the of the second frequency window;

obtaining a third window scan by scanning through the third frequency window; and

identifying the peak value from the third window scan.

6. The method of claim 1, wherein the step of displaying the calibrated spectral scans for the plurality of test positions to create a spectral-spatial scan for the test subject, further comprising the steps of:

displaying a circuit map corresponding to the test subject; and

displaying the calibrated spectral scans superimposed with the circuit map.

7. An apparatus operable for high-speed scanning of electromagnetic field levels associated with a test subject, the apparatus operable to perform the steps of:

for each of a plurality of spatially distinct test positions on the test subject;

(a) scanning an electromagnetic probe through a test frequency range to obtain a spectral scan representing electromagnetic field levels measured adjacent to the test position;

(b) identifying one or more peak values associated with the spectral scan;

(c) calculating a calibration curve fitting the peak values;

(d) applying the calibration curve to the spectral scan to create a calibrated spectral scan; and

displaying the calibrated spectral scans for the plurality of test positions to create a spectral-spatial scan for the test subject.

8. The apparatus of claim 7, wherein step (a) comprises scanning through the test frequency range multiple times.

9. The apparatus of claim 7, wherein step (b) comprises the steps of:

identifying one or more peak regions in the spectral scan; and

for each peak region,

selecting a first frequency window associated with the peak region, the first frequency window defining a subset of the of the test frequency range,

obtaining a first window scan by scanning through the first frequency window, and

identifying the peak value from the first window scan.

10. The apparatus of claim 9, wherein the step of identifying the peak value from the first window scan comprises the steps of:

identifying a second peak region within the first window scan, the second peak region defining a subset of the first peak region;

selecting a second frequency window associated with the second peak region, the second frequency window comprising a subset of the first frequency window;

obtaining a second window scan by scanning through the second frequency window; and

identifying the peak value from the second window scan.

11. The apparatus of claim 10, wherein the step of identifying the peak value from the second window scan comprises the steps of:

identifying a third peak region within the second window scan, the third peak region defining a subset of the second peak region;

selecting a third frequency window associated with the third peak region, the third frequency window comprising a subset of the of the second frequency window;

obtaining a third window scan by scanning through the third frequency window; and

identifying the peak value from the third window scan.

12. The apparatus of claim 7, further operable for displaying the calibrated spectral scans for the plurality of test positions to create a spectral-spatial scan for the test subject by:

displaying a circuit map corresponding to the test subject; and

displaying the calibrated spectral scans superimposed with the circuit map.

13. An apparatus operable for high-speed scanning of electromagnetic field levels associated with a test subject, comprising:

a plurality of probes, each probe operable for scanning through a test frequency range to measure electromagnetic field levels adjacent to the probe and within the test frequency range, each probe being positionable adjacent to a spatially distinct position on the test subject;

a synchronization block operable for synchronizing the operation of the probes;

a spectrum analyzer operable for receiving synchronized measurements from the probes and computing a synchronized set of spectral scans, each spectral scan corresponding to the measurements received from an associated probe; and

a computer operable for;

in one or more sequential sweeps, triggering the probes, the synchronization block, and the spectrum analyzer to produce synchronized electromagnetic field measurements across the test frequency range;

for each probe;

producing a spectral scan from the electromagnetic field measurements,

identifying one or more peak regions in the spectral scan, and

for each peak region,

selecting a first frequency window associated with the peak region, the first frequency window defining a subset of the of the test frequency range,

triggering the probe and the spectrum analyzer to produce a first window scan by scanning through the first frequency window, and

identifying a peak value from the first window scan;

calculating a calibration curve fitting the peak values,

applying the calibration curve to the spectral scan to create a calibrated spectral scan; and

displaying the calibrated spectral scans for the plurality of probes to create a spectral-spatial scan for the test subject.

14. The apparatus of claim 13, wherein the computer is further operable for displaying the calibrated spectral scans for the plurality of test positions to create a spectral-spatial scan for the test subject by:

displaying a circuit map corresponding to the test subject; and

displaying the calibrated spectral scans superimposed with the circuit map.