Estimating the operating point on a non-linear traveling wave tube amplifier

1. A method for determining an input operating point and an output operating point on a non-linear traveling wave tube amplifier (TWTA), comprising:

measuring non-linearity of the TWTA;

computing an input root-mean-square (RMS) value of an input signal used to measure the non-linearity of the TWTA, wherein the input RMS value identifies an input operating point of the measured non-linearity of the TWTA; and

obtaining an output operating point.

2. The method of claim 1 , wherein the measuring the non-linearity of the TWTA comprises measuring the non-linearity at a local receiver.

3. The method of claim 1 , wherein the measuring the non-linearity of the TWTA comprises measuring the non-linearity at a broadcast center.

4. The method of claim 3 , further comprising downloading the measured non-linearity and the output operating point to an individual receiver.

5. The method of claim 1 , wherein obtaining the output operating point comprises calculating an output RMS value of output signals used in measuring the non-linearity of the TWTA.

6. The method of claim 1 , wherein obtaining the output operating point comprises obtaining a corresponding point on the measured TWTA non-linearity based on the input RMS value.

7. The method of claim 1 , further comprising reconstructing an upper layer signal of a layered modulation based on the output operating point.

8. The method of claim 1 , further comprising offsetting the measured non-linearity to provide referenced operating point values.

9. The method of claim 8 , wherein the offsetting comprises scaling an input amplitude value and output amplitude value of the measured non-linearity of the TWTA to place the input and output operating points at desired points.

10. The method of claim 9 , wherein the scaling comprises subtracting a measured input operating point value from all input values in a log domain.

11. The method of claim 9 , wherein the scaling comprises subtracting a measured output operating point value from all output values in a log domain.

12. The method of claim 9 , wherein the scaling comprises subtracting a measured phase value at the output operating point from phase values of all output points used to measure the non-linearity of the TWTA.

13. The method of claim 9 , wherein the scaling further comprises:

placing bounding points beyond end points used to measure the non-linearity; and

interpolating output testing data that falls outside of the measured non-linearity based on the bounding points.

14. The method of claim 8 , further comprising mapping the input operating point and output operating point to a particular level to avoid signal saturation or fractional value representation overflow.

15. An apparatus for determining an input operating point and an output operating point on a non-linear traveling wave tube amplifier (TWTA), comprising:

means for measuring a non-linearity of the TWTA;

means for computing an input root-mean-square (RMS) value of an input signal used to measure the nonlinearity of the TWTA, wherein the input RMS value identifies an input operating point of the measured non-linearity of the TWTA; and

means for obtaining an output operating point.

16. The apparatus of claim 15 , wherein the means for measuring the non-linearity of the TWTA comprises means for measuring the non-linearity at a local receiver.

17. The apparatus of claim 15 , wherein the means for measuring the non-linearity of the TWTA comprises means for measuring the non-linearity at a broadcast center.

18. The apparatus of claim 17 , further comprising means for downloading the measured non-linearity and the output operating point to an individual receiver.

19. The apparatus of claim 15 , wherein the means for obtaining the output operating point comprises means for calculating an output RMS value of output signals used in measuring the non-linearity of the TWTA.

20. The apparatus of claim 15 , wherein the means for obtaining the output operating point comprises means for obtaining a corresponding point on the measured TWTA non-linearity based on the input RMS value.

21. The apparatus of claim 15 , further comprising means for reconstructing an upper layer signal of a layered modulation based on the output operating point.

22. The apparatus of claim 15 , further comprising means for offsetting the measured non-linearity to provide referenced operating point values.

23. The apparatus of claim 22 , wherein the means for offsetting comprises means for scaling an input amplitude value and output amplitude value of the measured non-linearity of the TWTA to place the input and output operating point at desired points.

24. The apparatus of claim 23 , wherein the means for scaling comprises means for subtracting a measured input operating point value from all input values in a log domain.

25. The apparatus of claim 23 , wherein the means for scaling comprises means for subtracting a measured output operating point value from all output values in a log domain.

26. The apparatus of claim 23 , wherein the means for scaling comprises means for subtracting a measured phase value at the output operating point from phase values of all output points used to measure the non-linearity of the TWTA.

27. The apparatus of claim 23 , wherein the means for scaling further comprises:

means for placing bounding points beyond end points used to measure the non-linearity; and

means for interpolating output testing data that falls outside of the measured non-linearity based on the bounding points.

28. The apparatus of claim 22 , further comprising means for mapping the input operating point and output operating point to a particular level to avoid signal saturation or fractional value representation overflow.

29. A system for determining an input operating point and an output operating point on a non-linear traveling wave tube amplifier (TWTA), comprising:

(a) a measuring module configured to:

(1) measure non-linearity of the TWTA; and

(2) obtaining an output operating point; and

(b) a non-linear distortion map module configured to compute an input root-mean-square (RMS) value of an input signal used to measure the non-linearity of the TWTA, wherein the RMS value identifies an input operating point of the measured non-linearity of the TWTA.

30. The system of claim 29 , wherein the measuring module is located at a local receiver.

31. The system of claim 29 , wherein the measuring module is located at a broadcast center.

32. The system of claim 31 , further comprising a receiver configured to download the measured non-linearity and the output operating point.

33. The system of claim 29 , wherein the measuring module is configured to obtain the output operating point by calculating an output RMS value of output signals used in measuring the non-linearity of the TWTA.

34. The system of claim 29 , wherein the measuring module is configured to obtain the output operating point by obtaining a corresponding point on the measured TWTA non-linearity based on the input RMS value.

35. The system of claim 29 , further comprising a receiver configured to reconstruct an upper layer signal of a layered modulation based on the output operating point.

36. The system of claim 29 , further comprising a receiver configured to offset the measured non-linearity to provide referenced operating point values.

37. The system of claim 36 , wherein the receiver is configured to offset the measured non-linearity by scaling an input amplitude value and output amplitude value of the measured non-linearity of the TWTA to place the input and output operating point at desired points.

38. The system of claim 37 , wherein the receiver is configured to scale by subtracting a measured input operating point value from all input values in a log domain.

39. The system of claim 37 , wherein the receiver is configured to scale by subtracting a measured output operating point value from all output values in a log domain.

40. The system of claim 37 , wherein the receiver is configured to scale by subtracting a measured phase value at the output operating point from phase values of all output points used to measure the non-linearity of the TWTA.

41. The system of claim 37 , wherein the receiver is further configured to scale by:

placing bounding points beyond end points used to measure the non-linearity; and

interpolating output testing data that falls outside of the measured non-linearity based on the bounding points.

42. The system of claim 36 , wherein the receiver is further configured to map the input operating point and output operating point to a particular level to avoid signal saturation or fractional value representation overflow.

43. The method of claim 2 , wherein the step of measuring the non-linearity of the TWTA comprises:

generating a difference between an ideal signal and a received signal.

44. The method of claim 43 , wherein generating a difference between an ideal signal and a received signal comprises:

demodulating the received signal;

decoding the demodulated signal;

generate the ideal signal; and

subtracting the ideal signal from the demodulated signal.

45. The method of claim 43 , wherein generating a difference between an ideal signal and a received signal comprises:

demodulating the received signal;

decoding the demodulated signal;

generating the ideal signal with a carrier of the received signal;

subtracting the ideal signal from the received signal.

46. The method of claim 2 , wherein the means for of measuring the non-linearity of the TWTA comprises:

generating a difference between an ideal signal and a received signal.

47. The method of claim 43 , wherein generating a difference between an ideal signal and a received signal comprises;

demodulating the received signal;

decoding the demodulated signal;

generate the ideal signal; and

subtracting the ideal signal from the demodulated signal.

48. The method of claim 43 , wherein generating a difference between an ideal signal and a received signal comprises:

demodulating the received signal;

decoding the demodulated signal;

generating the ideal signal with a carrier of the received signal;

subtracting the ideal signal from the received signal.