Method and apparatus for generating a pulse train with specifiable spectral response characteristics

• US 6,778,603 B1
• Filed: 11/08/2000
• Issued: 08/17/2004
• Est. Priority Date: 11/08/2000
• Status: Active Grant

• Current Assignee: Humatics Corporation
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Richards, James L., Fullerton, Larry W., Roberts, Mark D., Pendergrass, Marcus H.
• Primary Examiner(s): Tran, Khai
• Application Number:
  US09/708,025
• Time in Patent Office: 1,378 Days
• Field of Search: 375/238, 375/239, 375/295, 375/302, 375/242, 342/204, 342/202, 342/132, 342/375, 342/450
• US Class Current: 375/238
• CPC Class Codes: H04B 1/7172 Pulse shape in general H04L25/03834
• CPC Class Codes: H04B 1/7174 Pulse generation in general H04L25/03834

Abstract

A system and method for shaping the energy spectrum of a pulse train used by a pulse transmission system. The initial temporal and non-temporal characteristics of pulses comprising the pulse train are established using a designed code or a pseudorandom code and the spectral properties of the pulse train are determined. At least one characteristic of at least one pulse of the plurality of pulses that make up the pulse train are modified or at least one pulse is added or deleted to the pulse train and the spectral properties of the modified pulse train are determined. Whether or not the modification to the pulse train improved the energy spectrum relative to acceptance criteria is determined. The pulse train having the most desirable energy spectrum is selected. The optimization process can also iterate and may employ a variety of search algorithms.

Claims

1. A method for generating a code, comprising the steps of:

a. specifying at least one pulse;

b. calculating the spectral response of the at least one pulse;

c. modifying at least one pulse characteristic of the at least one pulse;

d. based on at least one modified pulse characteristic, selecting at least one pulse that meets a spectral response selection criteria; and

e. generating at least one code that specifies the at least one selected pulse.

2. The method of claim 1, wherein a pulse characteristic is at least one of:

a temporal pulse characteristic; and

a non-temporal pulse characteristic.

3. The method of claim 2, wherein said temporal pulse characteristic is a position in time.

4. The method of claim 2, wherein said non-temporal pulse characteristic is a pulse amplitude.

5. The method of claim 2, wherein said non-temporal pulse characteristic is a pulse width.

6. The method of claim 2, wherein said non-temporal pulse characteristic is a pulse polarity.

7. The method according to claim 6, wherein said pulse polarity indicates whether said pulse is inverted.

8. The method of claim 2, wherein said non-temporal pulse characteristic is a pulse type.

9. The method according to claim 8, wherein said pulse type indicates whether said pulse is any one of:

a square wave pulse;

a sawtooth pulse;

a Haar wavelet pulse;

a Gaussian monopulse;

a doublet pulse;

a triplet pulse; and

a set of wavelets.

10. The method of claim 1, wherein the at least one pulse is specified in accordance with an initial code.

11. The method of claim 10, wherein the initial code is generated using a numerical code generation technique.

12. The method of claim 11, wherein said numerical code generation technique comprises at least one of:

a Welch-Costas code generation technique;

a Golomb-Costas code generation technique;

a Quadratic Congruential code generation technique;

a Linear Congruential code generation technique;

a Hyperbolic Congruential code generation technique;

a linear congruential pseudorandom number generator technique;

an address lagged-Fibonacci pseudorandom number generator technique;

a linear feedback shift register pseudorandom number generator technique;

a lagged-Fibonacci shift register pseudorandom number generator technique;

a chaotic code pseudorandom number generator technique; and

an optimal Golomb ruler code pseudorandom number generator technique.

13. The method of claim 1, wherein the at least one pulse characteristic of the at least one pulse is modified in accordance with at least one pre-defined rule.

14. The method according to claim 13, wherein the at least one pre-defined rule corresponds to at least one characteristic value layout.

15. The method according to claim 14, wherein said at least one characteristic value layout specifies a range of pulse characteristic values.

16. The method according to claim 15, wherein said range of pulse characteristic values is subdivided into at least one of:

components;

sub-components of said components;

smaller components of said sub-components; and

even smaller components of said smaller components.

17. The method according to claim 16, wherein

each of said components is at least one of:

a same size, and

a different size than an other of said components;

each of said sub-components is at least one of;

a same size, and

a different size than an other of said sub-components;

each of said smaller components of said sub-components is at least one of;

a same size, and

a different size than an other of said smaller components of said subcomponents; and

each of said even smaller components of said smaller components is at least one of;

a same size, and

a different size than an other of said even smaller components of said smaller components.

18. The method according to claim 14, wherein said at least one characteristic value layout specifies at least one discrete pulse characteristic value.

19. The method of claim 14, wherein said at least one characteristic value layout specifies a range of pulse characteristic values and at least one discrete pulse characteristic value.

20. The method of claim 14, wherein said at least one characteristic value layout includes at least one non-allowable region specifying at least one non-allowed pulse characteristic value.

21. The method of claim 1, wherein the step of modifying at least one pulse characteristic of the at least one pulse comprises sequentially modifying at least one pulse characteristic of a plurality of pulses.

22. The method of claim 1, wherein the step of modifying at least one pulse characteristic of the at least one pulse comprises randomly modifying at least one pulse characteristic of a plurality of pulses.

23. The method of claim 1, wherein the step of modifying at least one pulse characteristic of the at least one pulse comprises modifying at least one pulse characteristic of a plurality of pulses based on a predefined order.

24. The method of claim 1, wherein calculating the spectral response of the at least one pulse comprises calculating the Fast Fourier Transform of the at least one pulse.

25. The method of claim 1, wherein calculating the spectral response of the at least one pulse comprises summing phasors for the at least one pulse at specified frequencies of a bandwidth.

26. The method of claim 1, further comprising the step of weighting the spectral response in accordance with a weighting curve.

27. The method of claim 1, wherein the spectral response selection criteria corresponds to at least one spectral density value.

28. The method of claim 1, wherein the spectral response selection criteria corresponds to at least one notch characteristic.

29. The method of claim 28, wherein the at least one notch characteristic corresponds to at least one of a notch location and notch width.

30. The method of claim 1, wherein the step of modifying at least one characteristic of at least one pulse comprises at least one of:

shifting one or more pulses;

adding one or more pulses;

deleting one or more pulses;

inverting one or more pulses;

changing the amplitude of one or more pulses;

changing the width of one or more pulses; and

changing the type of one or more pulses.

31. The method of claim 30, wherein pulse additions and deletions occur in tandem such that a number of a plurality of pulses is unchanged.

32. The method of claim 1, wherein the at least one pulse characteristic of the at least one pulse is modified in accordance with a pulse characteristic modification increment.

33. The method of claim 32, wherein the pulse characteristic modification increment is adjusted.

34. The method of claim 33, wherein the pulse characteristic modification increment is increased.

35. The method of claim 33, wherein the pulse characteristic modification increment is decreased.

36. The method of claim 1, wherein the at least one pulse characteristic of the at least one pulse is modified at random.

37. The method of claim 1, wherein the at least one pulse characteristic of the at least one pulse is modified using at least one of a:

Newton-Raphson method,

steepest descent method,

secant method,

conjugate gradients method,

first derivative test method, and

second derivative test method.

38. An apparatus operable for carrying out the steps of the method of claim 1.

39. A computer-readable storage device storing a set of computer executable instructions for performing the method of claim 1.