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

• US 9,197,282 B2
• Filed: 07/07/2014
• Issued: 11/24/2015
• 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): Perez, James M
• Application Number:
  US14/325,159
• Publication Number:
  US 20150063427A1
• Time in Patent Office: 505 Days
• Field of Search: 375130-153, 375/211, 375259-285, 375295-308
• US Class Current: 1/1
• 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, comprising:

a modulator configured to phase modulate a carrier signal utilizing a finite set of composite signal phases to combine three or more component signals, each having two or more phases, in order to generate and maintain the constant envelope composite signal; and

computation circuitry configured to determine the finite set of composite signal phases 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, said optimization process includes optimization of an objective function of the constant envelope of the composite signal.

2. The apparatus for generating a 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 2, wherein the inter-signal constraints are selected to minimize interference between signals that overlap in spectrum.

4. The apparatus for generating the composite signal of claim 3, wherein the component signals are M-ary digital modulations.

5. The apparatus for generating the composite signal of claim 3, wherein the component signals include Orthogonal Frequency Division Multiplexing (OFDM) component signals.

6. The apparatus for generating the composite signal of claim 3, wherein the component signals include Code Division Multiple Access (CDMA) component signals.

7. The apparatus for generating the composite signal of claim 3, wherein the component signals are pseudorandom noise (PRN) spreading codes.

8. The apparatus for generating the composite signal of claim 7, wherein the PRN spreading codes are at a plurality of different carrier frequencies.

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

10. The apparatus for generating the composite signal of claim 3, wherein the component signals are at a plurality of carrier frequencies.

11. The apparatus for generating the composite signal of claim 1, wherein the component signals are M-ary digital modulations.

12. The apparatus for generating the composite signal of claim 11, wherein the optimization process is further subject to one or more inter-signal constraints between the component signals.

13. The apparatus for generating the composite signal of claim 11, wherein the component signals include Orthogonal Frequency Division Multiplexing (OFDM) component signals.

14. The apparatus for generating the composite signal of claim 11, wherein the component signals include Code Division Multiple Access (CDMA) component signals.

15. The apparatus for generating the composite signal of claim 11, wherein the component signals are pseudorandom noise (PRN) spreading codes.

16. The apparatus for generating the composite signal of claim 15, wherein the PRN spreading codes are at a plurality of different carrier frequencies.

17. The apparatus for generating the composite signal of claim 11, wherein the component signals include satellite navigation signals.

18. The apparatus for generating the composite signal of claim 11, wherein the component signals are at a plurality of carrier frequencies.

19. A method for generating a constant envelope composite signal, comprising the steps of:

phase modulating a carrier signal with a modulator that uses a finite set of composite signal phases to combine three or more component signals, each having two or more phases, in order to generate the constant envelope composite signal,

determining, with computation circuitry, the finite set of composite signal phases 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, said optimization process includes optimization of an objective function of the constant envelope of the composite signal.

20. The method for generating the composite signal of claim 19, wherein the optimization process is further subject to one or more inter-signal constraints between the component signals.

21. The method for generating the composite signal of claim 20, wherein the inter-signal constraints are selected to minimize interference between signals that overlap in spectrum.

22. The method for forming the composite signal of claim 21, wherein the component signals are M-ary digital modulations.

23. The method for forming the composite signal of claim 21, wherein the component signals include Orthogonal Frequency Division Multiplexing (OFDM) component signals.

24. The method for forming the composite signal of claim 21, wherein the component signals include Code Division Multiple Access (CDMA) component signals.

25. The method for generating the composite signal of claim 21, wherein the component signals are pseudorandom noise (PRN) spreading codes.

26. The method for generating the composite signal of claim 25, wherein the PRN spreading codes are at a plurality of different carrier frequencies.

27. The method for generating the composite signal of claim 21, wherein the component signals include satellite navigation signals.

28. The method for forming the composite signal of claim 21, wherein the component signals are at a plurality of carrier frequencies.

29. The method for generating the composite signal of claim 19, wherein the component signals are M-ary digital modulations.

30. The method for forming the composite signal of claim 29, wherein the optimization process is further subject to one or more inter-signal constraints between the component signals.

31. The method for forming the composite signal of claim 29, wherein the component signals include Orthogonal Frequency Division Multiplexing (OFDM) component signals.

32. The method for forming the composite signal of claim 29, wherein the component signals include Code Division Multiple Access (CDMA) component signals.

33. The method for forming the composite signal of claim 29, wherein the component signals are pseudorandom noise (PRN) spreading codes.

34. The method for generating the composite signal of claim 33, wherein the PRN spreading codes are at a plurality of different carrier frequencies.

35. The method for forming the composite signal of claim 29, wherein the component signals include satellite navigation signals.

36. The method for forming the composite signal of claim 29, wherein the component signals are at a plurality of carrier frequencies.