Phase-optimized constant envelope transmission (POCET) method, apparatus and system

• US 8,774,315 B2
• Filed: 08/25/2009
• Issued: 07/08/2014
• Est. Priority Date: 08/25/2009
• Status: Active Grant

• Current Assignee: Aerospace Corporation
• Original Assignee: Aerospace Corporation
• Inventors: Cahn, Charles Robert, Dafesh, Philip A.
• Primary Examiner(s): Ahn, Sam K
• Assistant Examiner(s): Perez, James M
• Application Number:
  US12/547,383
• Publication Number:
  US 20110051783A1
• Time in Patent Office: 1,778 Days
• Field of Search: 375295-308, 375130-153, 375/211, 375259-285
• US Class Current: 375/297
• CPC Class Codes: G01S 19/02 Details of the space or ground control segments
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 2001/0491 with frequency synthesizers, frequency converters or modulators
• CPC Class Codes: H04B 2201/70706 with means for reducing the peak-to-average power ratio
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/0003 Code application, i.e. aspects relating to how codes are applied to form multiplexed channels
• CPC Class Codes: H04L 23/02 adapted for orthogonal signalling
• CPC Class Codes: H04L 27/12 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 27/2007 in which the phase change within each symbol period is constrained coset coding H04L27/186

Abstract

An apparatus and method for generating a composite signal includes electronics configured to modulate a carrier utilizing a finite set of composite signal phases to generate a composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes a constant envelope for the phase modulated carrier, subject to constraints on desired signal power levels of the signals to be combined and either zero or one or more relative phase relationships between the signals. The apparatus and method can be extended to generating an optimized composite signal of different frequencies.

Claims

1. An apparatus for generating a constant envelope composite signal from a plurality of component signals, comprising:

a synthesizer configured to generated a carrier signal; and

electronics configured to modulate the carrier signal utilizing a finite set of composite signal phases to combine three or more component signals, each having two or more possible phases to generate and maintain the constant envelope composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes the constant envelope of the composite signal, subject to a plurality of intra-signal constraints for the component signals,

wherein said optimization process includes optimization of an objective function of the constant envelope of the composite signal.

2. The apparatus for generating the composite signal of claim 1, wherein the optimization process is further subject to one or more inter-signal constraints between the component signals.

3. The apparatus for generating the composite signal of claim 1, wherein the component signals are satellite navigation signals.

4. The apparatus for generating the composite signal of claim 1, wherein the intra-signal constraints are formed from intra-signal desired power constraints, each of the intra-signal constraints being formed as a function of all possible phase states.

5. The apparatus for generating the composite signal of claim 4, wherein the intra-signal constraints are determined from the desired component signal power levels.

6. The apparatus for generating the composite signal of claim 1, wherein the finite set of composite signal phases are phase values precomputed as a deterministic function of the component signals to produce the constant envelope composite signal.

7. The apparatus for generating the composite signal of claim 1, wherein the optimization process includes utilizing a penalty function to produce a deterministic table comprised of the finite set of composite signal phases for modulating the carrier.

8. The apparatus for generating the composite signal of claim 1, wherein the constant envelope composite signal is formed from Orthogonal Frequency Division Multiplexing (OFDM) component signals.

9. The apparatus for generating the composite signal of claim 1, wherein the constant envelope composite signal is formed from Code Division Multiple Access (CDMA) component signals.

10. The apparatus for generating the composite signal of claim 1, wherein the component signals are pseudorandom noise (PRN) spreading codes.

11. The apparatus for generating the composite signal of claim 10, wherein the PRN spreading codes are at a plurality of different carrier frequencies.

12. The apparatus for generating the composite signal of claim 1, wherein the composite signal is derived from Frequency Division Multiple Access (FDMA) component signals.

13. The apparatus for generating the composite signal of claim 1, wherein each of the component signals is at a plurality of carrier frequencies.

14. The apparatus for generating the composite signal of claim 1, wherein the electronics include a modulator configured to utilize multiple finite sets of optimized phase tables, determined through additional optimization processes to accommodate different carrier frequencies.

15. The apparatus for generating the composite signal of claim 14, wherein a number of additional optimizations performed corresponds to a number of phase steps associated with the component signals at a plurality of different carrier frequencies.

16. The apparatus for generating the composite signal of claim 15, wherein the number of phase steps associated with the different carrier frequencies is determined by quantizing the continuous phase rotation of the carrier to ensure a negligible correlation loss.

17. An apparatus for generating a constant envelope composite signal from a plurality of component signals, comprising:

a synthesizer configured to generated a carrier signal; and

electronics configured to modulate the carrier signal utilizing a finite set of composite signal phases to combine three or more component signals, each having two or more possible phases to generate and maintain the constant envelope composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes the constant envelope of the composite signal, subject to a plurality of constraints on desired signal power levels for the component signals,

wherein said optimization process includes optimization of an objective function of the constant envelope of the composite signal.

18. The apparatus for generating the composite signal of claim 17, wherein the optimization process is further subject to one or more constraints on phase relationships between the component signals.

19. The apparatus for generating the composite signal of claim 17, wherein the component signals are satellite navigation signals.

20. The apparatus for generating the composite signal of claim 17, wherein the optimization process is further subject to the constraints on desired signal power levels, each of the constraints being formed as a function of all possible phase states.

21. The apparatus for generating the composite signal of claim 20, wherein the constraints are determined from the desired signal correlation levels.

22. The apparatus for generating the composite signal of claim 17, wherein the finite set of composite signal phases are phase values precomputed as a deterministic function of the component signals to produce the constant envelope composite signal.

23. The apparatus for generating the composite signal of claim 17, wherein the optimization process includes utilizing a penalty function to produce a deterministic table comprised of the finite set of composite signal phases for modulating the carrier.

24. The apparatus for generating the composite signal of claim 17, wherein the constant envelope composite signal is formed from Orthogonal Frequency Division Multiplexing (OFDM) component signals.

25. The apparatus for generating the composite signal of claim 17, wherein the constant envelope composite signal is formed from Code Division Multiple Access (CDMA) component signals.

26. The apparatus for generating the composite signal of claim 17, wherein the component signals are pseudorandom noise (PRN) spreading codes.

27. The apparatus for generating the composite signal of claim 26, wherein the PRN spreading codes are at a plurality of different carrier frequencies.

28. The apparatus for generating the composite signal of claim 17, wherein the composite signal is derived from Frequency Division Multiple Access (FDMA) component signals.

29. The apparatus for generating the composite signal of claim 17, wherein each of the component signals is at a plurality of carrier frequencies.

30. The apparatus for generating the composite signal of claim 17, wherein the electronics include a modulator configured to utilize multiple finite sets of optimized phase tables, determined through additional optimization processes, to accommodate different carrier frequencies.

31. The apparatus for generating the composite signal of claim 17, wherein a number of additional optimizations performed corresponds to a number of phase steps associated with the component signals at a plurality of different carrier frequencies.

32. The apparatus for generating the composite signal of claim 31, wherein the number of phase steps associated with the different carrier frequencies is determined by quantizing the continuous phase rotation of the carrier to ensure a negligible correlation loss.

33. A method for generating a constant envelope composite signal from a plurality of component signals, comprising the steps of:

generating a carrier signal; and

modulating the carrier signal utilizing a finite set of composite signal phases to combine three or more component signals, each having two or more possible phases to generate the constant envelope composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes the constant envelope of the composite signal, while maintaining a plurality of constraints on desired signal power levels for the component signals, and zero or more constraints on phase relationships between the component signals,

wherein said optimization process includes optimization of an objective function of the constant envelope of the composite signal.

34. The method for generating the composite signal of claim 33, wherein the component signals are satellite navigation signals.

35. The method for generating the composite signal of claim 33, wherein the component signals are pseudorandom noise (PRN) spreading codes.

36. The method for generating the composite signal of claim 35 wherein the PRN spreading codes are at a plurality of different carrier frequencies.

37. The method for generating the composite signal of claim 33, wherein each of the component signals is at a plurality of carrier frequencies.

38. The method for generating the composite signal of claim 33, further including the step of:

utilizing multiple finite sets of optimized phase tables, determined through additional optimization processes, to accommodate different carrier frequencies.

39. A method for forming a constant envelope composite signal from a plurality of N component signals, comprising the steps of:

enumerating M^N phase states for combining the N component signals, each having M possible signal phases, where N is a positive integer ≧

3 and M is a positive integer ≧

2;

formulating N intra-signal constraint equations, each as a function of the M^N phase states, to provide intra-signal constraints on the component signals;

formulating K inter-signal constraint equations, where 0≦

K≦

N(N−

1)/2, each as a function of the M^N phase states, to provide inter-signal constraints between the component signals;

performing an optimization process to minimize the constant envelope composite signal, subject to the intra-signal constraints on the component signals and the inter-signal constraints between the component signals; and

modulating a Radio Frequency (RF) carrier using the phase states determined through the optimization process to produce the constant envelope composite signal from the N component signals,

wherein performing said optimization process includes optimization of an objective function that minimizes the constant envelope of the composite signal.

40. The method for forming the composite signal of claim 39, wherein performing said optimization process includes optimization of the objective function for the power of the constant envelope composite signal.

41. The method for forming the composite signal of claim 40, wherein said optimization algorithm is used to minimize the objective function.

42. The method for forming the composite signal of claim 39, wherein performing said optimization process includes utilizing a penalty function method.

43. The method for forming the composite signal of claim 39, wherein the constant envelope composite signal includes Orthogonal Frequency Division Multiplexing (OFDM) component signals.

44. The method for forming the composite signal of claim 39, wherein the constant envelope composite signal includes Code Division Multiple Access (CDMA) component signals.

45. The method for generating the composite signal of claim 39, wherein the component signals are pseudorandom noise (PRN) spreading codes.

46. The method for generating the composite signal of claim 45, wherein the PRN spreading codes are at a plurality of different carrier frequencies.

47. The method for generating the composite signal of claim 39, wherein each of the component signals is at a plurality of carrier frequencies.

48. The method for forming the composite signal of claim 39, wherein the composite signal includes Frequency Division Multiple Access (FDMA) signals.

49. The method for forming the composite signal of claim 39, further including the step of:

performing additional optimization processes for different carrier frequencies.

50. The method for forming the composite signal of claim 49, wherein a number of additional optimizations performed corresponds to a number of phase steps associated with the different carrier frequencies.

51. The method for forming the composite signal of claim 50, wherein the number of phase steps associated with the different carrier frequencies is determined by quantizing the continuous phase rotation of the RF carrier to ensure a negligible correlation loss.

52. A method for forming a constant envelope composite signal from a plurality of N component signals, comprising the steps of:

enumerating M^N phase states for combining the N component signals, each having M possible signal phases, where N is a positive integer ≧

3 and M is a positive integer ≧

2;

formulating N intra-signal constraint equations, each as a function of the M^N phase states, to provide intra-signal constraints on the component signals;

formulating K inter-signal constraint equations, where 0≦

K≦

N(N−

1)/2, each as a function of the M^N phase states, to provide inter-signal constraints between the component signals;

performing an optimization process to minimize the constant envelope composite signal, subject to the intra-signal constraints on the component signals and the inter-signal constraints between the component signals;

modulating a Radio Frequency (RF) carrier using the phase states determined through the optimization process to produce the constant envelope composite signal from the N component signals; and

performing additional said optimization processes for different carrier frequencies,

wherein a number of additional said optimizations performed corresponds to a number of phase steps associated with the different carrier frequencies, and

wherein the number of phase steps associated with the different carrier frequencies is determined by quantizing the continuous phase rotation of the RF carrier to ensure a negligible correlation loss.

53. An apparatus for generating a constant envelope composite signal from a plurality of component signals, comprising:

a synthesizer configured to generated a carrier signal; and

electronics configured to modulate the carrier signal utilizing a finite set of composite signal phases to combine three or more component signals, each having two or more possible phases to generate and maintain the constant envelope composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes an objective function comprising the constant envelope of the composite signal, subject to a plurality of intra-signal constraints for the component signals,

wherein the electronics include a modulator configured to utilize multiple finite sets of optimized phase tables, determined through additional said optimization processes to accommodate different carrier frequencies,

wherein a number of additional said optimizations performed corresponds to a number of phase steps associated with the component signals at a plurality of different carrier frequencies, and

wherein the number of phase steps associated with the different carrier frequencies is determined by quantizing the continuous phase rotation of the carrier to ensure a negligible correlation loss.

54. An apparatus for generating a constant envelope composite signal from a plurality of component signals, comprising:

a synthesizer configured to generated a carrier signal; and

electronics configured to modulate the carrier signal utilizing a finite set of composite signal phases to combine three or more component signals, each having two or more possible phases to generate and maintain the constant envelope composite signal, the finite set of composite signal phases being determined through an optimization process that minimizes an objective function comprising the constant envelope of the composite signal, subject to a plurality of constraints on desired signal power levels for the component signals,

wherein the electronics include a modulator configured to utilize multiple finite sets of optimized phase tables, determined through additional said optimization processes, to accommodate different carrier frequencies,

wherein a number of additional said optimizations performed corresponds to a number of phase steps associated with the component signals at a plurality of different carrier frequencies, and

wherein the number of phase steps associated with the different carrier frequencies is determined by quantizing the continuous phase rotation of the carrier to ensure a negligible correlation loss.