Network analyzer applying loss compensation using port extensions and method of operation

• US 7,054,780 B2
• Filed: 09/13/2004
• Issued: 05/30/2006
• Est. Priority Date: 09/13/2004
• Status: Expired due to Fees

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Bender, Doug, Blackham, David, Dunsmore, Joel
• Primary Examiner(s): Raymond, Edward
• Application Number:
  US10/939,861
• Publication Number:
  US 20060074582A1
• Time in Patent Office: 624 Days
• Field of Search: 702/117, 702/118, 702182-185, 702/188, 714/100, 714/4, 714/5, 714/25, 714/30, 714/48, 714/1, 707/1
• US Class Current: 702/117
• 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
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

In one embodiment, a method of operating a network analyzer, comprises applying a stimulus signal on at least one port of the network analyzer for provision to a device under test (DUT) within a test fixture coupled to the network analyzer; generating measurement data from the DUT in response to the stimulus signal on at least one port of the network analyzer; and generating an amplitude response of the DUT across a frequency range, wherein a port extension module of the network analyzer automatically applies loss compensation to the amplitude response in a manner that is non-linearly related to frequency according to at least one controllable parameter.

Claims

1. A method of operating a network analyzer, comprising:

applying a stimulus signal on at least one port of said network analyzer for provision to a device under test (DUT) within a test fixture coupled to said network analyzer;

generating measurement data from said DUT in response to said stimulus signal on at least one port of said network analyzer; and

generating an amplitude response of said DUT across a frequency range, wherein a port extension module of said network analyzer automatically applies loss compensation to said amplitude response in a manner that is non-linearly related to frequency according to at least one controllable parameter.

2. The method of claim 1 wherein said port extension calculates loss compensation values using the formula:

a·

f^1/2+b·

f,

wherein a and b are parameters and f is a variable representing frequency.

3. The method of claim 2 wherein said port extension further calculates said loss compensation values by adding a DC loss value to said formula.

4. The method of claim 1 wherein said port extension calculates loss compensation values using the formula:

a·

f^b,

wherein a and b are parameters and f is a variable representing frequency.

5. The method of claim 4 wherein parameters a and b are controllable.

6. The method of claim 4 wherein said port extension further calculates said loss compensation values by adding a DC loss value to said formula.

7. The method of claim 1 wherein said port extension module calculates a first loss compensation value associated with a first port to which said stimulus signal is applied and a second loss compensation value associated with a second port on which measurements are made.

8. The method of claim 1 further comprising:

receiving, by the network analyzer, input from the user to modify said controllable parameter.

9. The method of claim 8 further comprising:

repeating said applying, generating measurement data, and generating an amplitude response in response to said modified controllable parameter during real-time operation of said network analyzer.

10. The method of claim 1 further comprising:

receiving, by the network analyzer, input from the user to cause said network analyzer to automatically calibrate said controllable parameter.

11. The method of claim 1 wherein said controllable parameter is automatically modified by said network analyzer in response to a user modifying a delay value associated with said port extension module.

12. The method of claim 1 wherein said controllable parameter is calculated by multiplying a loss parameter by a delay value associated with said port extension module.

13. A method of calibrating a network analyzer, comprising:

applying a stimulus signal on a port of said network analyzer for provision to a test fixture coupled to said network analyzer;

generating measurement data from said test fixture in response to said stimulus signal on said port of said network analyzer;

generating an amplitude response of said test fixture across a frequency range;

applying, by a port extension calibration module of said network analyzer, a parameter fitting algorithm to said amplitude response using a function of frequency characterized by a plurality of parameters; and

configuring a port extension module to apply loss compensation to measurements associated with said port on a non-linear frequency dependent basis according to said function and said plurality of parameters determined by said fitting algorithm.

14. The method of claim 13 wherein said function is given by:

a·

f^1/2+b·

f,

wherein a and b are parameters and f is a variable representing frequency.

15. The method of claim 14 wherein said fitting algorithm is a polynomial fitting algorithm.

16. The method of claim 14 further comprising:

calculating a DC loss value for addition to said function, wherein said configuring adjusts said port extension module to apply loss compensation using said DC loss value.

17. The method of claim 16 wherein said calculating a DC loss value includes determining an offset to prevent a loss compensated amplitude response of said test fixture from being greater than one.

18. The method of claim 13 wherein said function is given by:

a·

f^b,

wherein a and b are parameters and f is a variable representing frequency.

19. The method of claim 18 wherein said fitting algorithm is a line fitting algorithm.

20. The method of claim 18 further comprising:

calculating a DC loss value for addition to said function, wherein said configuring adjusts said port extension module to apply loss compensation using said DC loss value.

21. The method of claim 20 wherein said calculating a DC loss value includes determining an offset to prevent a loss compensated amplitude response of said test fixture from being greater than one.

22. The method of claim 13 wherein said measurement data is obtained using an open standard.

23. The method of claim 13 wherein said measurement data is obtained using a short standard.

24. The method of claim 13 wherein said measurement data is an average of measurement data obtained using a short standard and an open standard.

25. A method of calibrating a network analyzer, comprising:

applying a stimulus signal on a port of said network analyzer for provision to a test fixture coupled to said network analyzer;

generating measurement data from said test fixture in response to said stimulus signal on said port of said network analyzer;

generating an amplitude response of said test fixture across a frequency range;

applying, by a port extension calibration module of said network analyzer, at least one loss value to a first function to derive a parameter at least partially characterizing said amplitude response of test fixture; and

configuring a port extension module to apply loss compensation to measurements associated with said port on a non-linear frequency dependent basis according to a second function that is a function of frequency and is at least partially characterized by at least said parameter.

26. The method of claim 25 wherein said second function is given by:

a·

f^1/2+b·

f,

wherein a and b are parameters and f is a variable representing frequency.

27. The method of claim 26 wherein parameters a and b are determined by the following equations:

a=(L₁f₂−

L₂f₁)/(f₂f₁^1/2−

f₁f₂^1/2), and

b=(L₁f₂^1/2−

L₂f₁^1/2)/(f₁f₂^1/2−

f₂f₁^1/2),

wherein L₁ and L₂ are loss values and f₁ and f₂ are frequencies corresponding to said loss values.

28. The method of claim 26 further comprising:

calculating a DC loss value for addition to said second function, wherein said configuring adjusts said port extension module to apply loss compensation using said DC loss value.

29. The method of claim 28 wherein said calculating a DC loss value includes determining an offset to prevent a loss compensated amplitude response of said test fixture from being greater than one.

30. The method of claim 25 wherein said second function is given by:

a·

f^b,

wherein a and b are parameters and f is a variable representing frequency.

31. The method of claim 30 wherein parameters a and b are determined by the following equations:

a=exp{(ln(f₂)ln(L₁)−

ln(f₁)ln(L₂))/(ln(f₂)−

ln(f₁)}, and

b=ln(L₁/L₂)/ln(f₁/f₂),

wherein L₁ and L₂ are loss values and f₁ and f₂ are frequencies corresponding to said loss values.

32. The method of claim 30 further comprising:

calculating a DC loss value for addition to said second function, wherein said configuring adjusts said port extension module to apply loss compensation using said DC loss value.

33. The method of claim 32 wherein said calculating a DC loss value includes determining an offset to prevent a loss compensated amplitude response of said test fixture from being greater than one.

34. The method of claim 25 wherein said measurement data is obtained using an open standard.

35. The method of claim 25 wherein said measurement data is obtained using a short standard.

36. The method of claim 25 wherein said measurement data is an average of measurement data obtained using a short standard and an open standard.

37. A network analyzer, comprising:

a plurality of ports for application of stimulus signals to a device under test (DUT) and for measuring signals from said DUT;

signal processing logic for performing spectral analysis of measurements made on said plurality of ports, wherein said signal processing logic applies port extension loss compensation to amplitude data generated by said spectral analysis;

logic for processing reflection measurement data, during a calibration mode of said network analyzer, to generate estimates of loss associated with a test fixture; and

logic for adjusting port extension settings in response to said logic for processing.

38. The network analyzer of claim 37 wherein said signal processing logic evaluates a function is given by:

a·

f^1/2+b·

f,

wherein a and b are said parameters and f is a variable representing frequency.

39. The network analyzer of claim 37 wherein said logic for processing applies a polynomial fitting algorithm.

40. The method of claim 38 further comprising:

calculating a DC loss value for addition to said function for said port extension loss compensation.

41. The method of claim 40 wherein said calculating a DC loss value includes determining an offset to prevent a loss compensated amplitude response of said test fixture from being greater than one.

42. The network analyzer of claim 37 wherein said signal processing logic evaluates a function is given by:

a·

f^b,

wherein a and b are parameters and f is a variable representing frequency.

43. The network analyzer of claim 42 wherein said logic for processing applies a line fitting algorithm.

44. The method of claim 42 further comprising:

calculating a DC loss value for addition to said function for said port extension loss compensation.

45. The method of claim 44 wherein said calculating a DC loss value includes determining an offset to prevent a loss compensated amplitude response of said test fixture from being greater than one.