MODULATION SIGNATURE TRIGGER

• US 20090094495A1
• Filed: 10/09/2007
• Published: 04/09/2009
• Est. Priority Date: 10/09/2007
• Status: Active Grant

• Current Assignee: Tektronix Incorporated (Fortive Corp.)
• Original Assignee: Tektronix Incorporated (Fortive Corp.)
• Inventors: TORIN, SHIGETSUNE
• Granted Patent: US 7,816,904 B2
• Time in Patent Office: Days
• US Class Current: 714/732
• CPC Class Codes: G01R 13/0254 for triggering, synchronisation
• CPC Class Codes: G01R 23/16 Spectrum analysis; Fourier analysis

Abstract

A trigger generator and trigger method are provided for determining whether or not a signal under test matches a modulation signature. The modulation signature may be provided as a magnitude signature, a phase signature or both. When the magnitude values, phase values, or both of a signal under test are the same as their respective modulation signature, an error computation will be close to zero. If this value is within a threshold value, a trigger signal or other indication of a match is produced.

Claims

1. A test and measurement instrument comprising:

a signal input to obtain magnitude values or phase values corresponding to a signal under test;

a detector to compare the magnitude values, or the phase values against a modulation signature; and

a comparator to generate a trigger signal when the detector output is within a threshold value.

2. The test and measurement instrument of claim 1, further comprising a shift register to move the signal under test relative to the modulation signature.

3. The test and measurement instrument of claim 1, wherein the modulation signature is a magnitude signature.

4. The test and measurement instrument of claim 3, wherein the magnitude signature is scaled to reduce an error vector calculated by the detector.

5. The test and measurement instrument of claim 3, wherein the magnitude signature is offset to reduce an error vector calculated by the detector.

6. The test and measurement instrument of claim 1, wherein the modulation signature is a phase signature.

7. The test and measurement instrument of claim 6, wherein the detector compares the difference between the phase values of the signal under test and the phase signature.

8. The test and measurement instrument of claim 7, wherein the detector applies weighting based upon a magnitude signature corresponding to the phase signature.

9. The test and measurement instrument of claim 1, wherein the signal input is obtained from a storage medium, and the detector and the comparator are implemented in software running on a processor.

10. The test and measurement instrument of claim 1, wherein the input signal is retrieved from a storage medium and processed using the detector and the comparator implemented as hardware within a trigger generator circuit to provide post process analysis.

11. A method of identifying a signal data matching a modulation trigger comprising:

obtaining magnitude values or phase values for a signal under test;

comparing the magnitude values or phase values against a modulation signature;

indicating that a portion of the signal under test matches the modulation signature.

12. The method of claim 11, wherein the modulation signature is magnitude signature scaled to reduce an error value associated with comparing the magnitude values against the magnitude signature.

13. The method of claim 11, wherein the modulation signature is a magnitude signature offset to reduce an error value associated with comparing the magnitude values against the magnitude signature.

14. The method of claim 11, wherein the modulation signature is a phase signature scaled to reduce an error value associated with comparing the phase values against the phase signature.

15. The method of claim 11, wherein the modulation signature is a phase signature that is frequency offset to reduce an error value associated with comparing the phase values against the phase signature.

16. The method of claim 11, wherein the modulation signature is a phase signature that is constant phase shifted to reduce an error value associated with comparing the phase values against the phase signature.

17. The method of claim 11, wherein the step of comparing phase values against a modulation signature further comprises subtracting a phase signature from the phase values to obtain a phase differences signal.

18. The method of claim 17, further comprising calculating a straight line fit to the phase differences.

19. The method of claim 18, further comprising providing a magnitude signature along with a phase signature and applying a weighting factor based upon the magnitude signature when calculating the straight line fit.