Bandwidth analysis system and method

• US 5,119,017 A
• Filed: 10/12/1990
• Issued: 06/02/1992
• Est. Priority Date: 10/12/1990
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Labarre, Gary K., Gee, Timothy E.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): Solis, Jose M.
• Application Number:
  US07/597,917
• Time in Patent Office: 599 Days
• Field of Search: 364/485, 364/487, 382/29, 382/11, 382/17, 382/64, 324/77 R, 324/77 A, 324/77 B, 324/78 R, 324/78 D, 324/79 D
• US Class Current: 324/76.19
• CPC Class Codes: G01R 23/16 Spectrum analysis; Fourier analysis
• CPC Class Codes: G01R 27/28 Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response in line transmission systems H04B3/46

Abstract

The present invention is a system and method that uses a digital spectrum analyzer to digitize a spectrum and loads the digitized spectrum into a computer. The computer scans the spectrum to determine a zero dB reference by cyclic averaging and determines the upper and lower cutoff frequencies using inward and outward scan techniques which are averaged. During zero dB level determination holes in the spectrum are ignored and during upper and lower cutoff frequency determination the holes or drop outs in the spectrum are located, counted and characterized.

Claims

1. A bandwidth analysis system, comprising:

spectrum capture means for analyzing a signal and producing a frequency spectrum of the signal; and

analysis means for determining a bandwidth of the spectrum, detecting a hole in the spectrum and determining characteristics of the hole in the spectrum.

2. A system as recited in claim 1, wherein said analysis means determines one of:

a center frequency of the spectrum, upper and lower cut off frequencies of the spectrum, maximum power and a frequency at the maximum power, minimum power and a frequency at the minimum power, bandwidth ripple, bandwidth rejection, a baseline and average band power.

3. A system as recited in claim 1, wherein said analysis means determines one of:

hole center frequency, hole width and hole depth.

4. A system as recited in claim 1, wherein said analysis means determines detects the hole by comparing spectrum data values with a minimum hole width and a minimum hole depth provided by a user.

5. A system as recited in claim 1, wherein said analysis means determines the bandwidth by scanning spectrum data inward from edges of the spectrum to determine outside leading and trailing edge cutoff points by comparing spectrum data to a cutoff level provided by the user, scanning the spectrum data outward from a maximum spectrum value point to determine inside leading and trailing edge cutoff points, averaging the inside and outside leading edge cutoff points and averaging the inside and outside trailing edge cutoff points.

6. A system as recited in claim 5, wherein said analysis means excludes as inside edge points data points outside a predetermined range from the outside edge cutoff points.

7. A system as recited in claim 1, wherein said analysis means excludes holes form zero level determination calculations during bandwidth determination.

8. A system as recited in claim 7, wherein said analysis means determines a zero level by averaging.

19. A system as recited in claim 1, wherein said analysis means comprises a computer.

21. A system as recited in claim 1, wherein said analysis means detects the hole by using a minimum hole size.

9. A bandwidth analysis system, comprising:

spectrum capture means for analyzing a signal and producing a frequency spectrum of the signal; and

analysis means for determining a zero reference level, a bandwidth and characteristics of a hole in the spectrum by detecting the hole by comparing spectrum data values with a minimum hole width and a minimum hole depth provided by a user, determining the bandwidth by scanning spectrum data inward from edges of the spectrum to determine outside leading and trailing edge cutoff points by comparing spectrum data to a cutoff level provided by the user, scanning the spectrum data outward from a maximum spectrum value point, while characterizing the holes, to determine inside leading and trailing edge cutoff points, averaging the inside and outside leading edge cutoff points and averaging the inside and outside trailing edge cutoff points, excluding as inside edge points data points outside a predetermined range from the outside edge cutoff points, and excluding holes from the zero level determination calculations during bandwidth determination.

20. A system as recited in claim 9, wherein said analysis means comprises a computer.

22. A system as recited in claim 9, wherein said analysis means detects the hole by using a minimum hole size.

10. A method of bandwidth analysis, comprising:

(a) capturing a spectrum of a signal;

(b) scanning the spectrum to find a reference level using a computer;

(c) determining, using the computer, a bandwidth from a predetermined cutoff level and the reference level and excluding spectrum holes from the bandwidth determination by detecting the holes; and

(d) calculating, using the computer, spectrum characteristics from the spectrum, the reference level and the bandwidth.

11. A method as recited in claim 10, wherein step (b) excludes spectrum holes from reference level determination.

12. A method as recited in claim 11, wherein holes are excluded by comparing spectrum data to a minimum hole width and a minimum hole depth.

13. A method as recited in claim 10, wherein holes in the spectrum are counted and characterized.

14. A method as recited in claim 10, wherein step (b) comprises:

(1) averaging a predetermined number of data points around a spectrum apex;

(2) determining a first level from the average.

(3) scanning the spectrum from the edges to find first leading and trailing edge points where the data points cross the first level;

(4) averaging the data points between the first leading and trailing edge points as a second level;

(5) scanning the spectrum from the edges to find second leading and trailing edge points where the data points cross the second level; and

(6) averaging the data points between the second leading and trailing edge points as the reference level.

15. A method as recited in claim 10, wherein step (c) comprises:

(1) determining a cutoff value from the reference level and the predetermined cutoff level;

(2) scanning the spectrum from the edges inward to find outside leading and trailing edge points where spectrum data points cross the cutoff value;

(3) scanning the spectrum from a spectrum apex outward to find inside leading and trailing edge points within a predetermined range of the outside leading and trailing edge points where the spectrum data points cross the cutoff value;

(4) averaging the inside and outside leading edge points and averaging the inside and outside trailing edge points; and

(5) subtracting the averaged leading and trailing edge points.

16. A method as recited in claim 11, wherein hole exclusion comprises:

(1) scanning the spectrum to determine . hole depth and hole width and saving hole width and value data;

(2) comparing the hole width data and value data to a hole minimum width and a hole minimum depth; and

(3) combining the saved hole width and value data with reference level data when the comparison indicates a hole does not exist.

17. A method as recited in claim 13, wherein hole counting and characterization comprise:

(1) scanning the spectrum to determine hole depth and hole width and saving hole width and value data;

(2) comparing the hole width data and value data to a hole minimum width and a hole minimum depth; and

(3) determining hole width, hole depth and hole center frequency from the saved hole width and value data when the comparison indicates a hole exists.

23. A method as recited in claim 10, wherein step (c) detects the holes using a minimum hole size.

18. A method of measuring a hole in a spectrum, comprising:

(a) capturing a spectrum of a signal;

(b) scanning the spectrum to detect the hole and determine location and size characteristics of the hole in the spectrum using a computer;

(c) capturing a narrower span of the spectrum around the located hole; and

(d) scanning the narrower span of the spectrum determining cutoff levels and a bandwidth of the located hole using the computer.

24. A method as recited in claim 18, wherein step (b) detects the holes using a minimum hole size.