Hybrid spread spectrum radio system

• US 7,660,338 B2
• Filed: 12/29/2006
• Issued: 02/09/2010
• Est. Priority Date: 12/31/2003
• Status: Expired due to Fees

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Dress, William B., Smith, Stephen F.
• Primary Examiner(s): BURD, KEVIN MICHAEL
• Application Number:
  US11/648,021
• Publication Number:
  US 20080019422A1
• Time in Patent Office: 1,138 Days
• Field of Search: 375130-132, 375/136, 375/140, 375/147, 375/295, 375/316
• US Class Current: 375/131
• CPC Class Codes: H04B 1/692 Hybrid techniques using combinations of two or more spread spectrum techniques
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/713 using frequency hopping

Abstract

Systems and methods are described for hybrid spread spectrum radio systems. A method, includes receiving a hybrid spread spectrum signal including: fast frequency hopping demodulating and direct sequence demodulating a direct sequence spread spectrum signal, wherein multiple frequency hops occur within a single data-bit time and each bit is represented by chip transmissions at multiple frequencies.

Claims

1. A method that improves a processing gain of a signal comprising:

receiving a fast frequency hopped direct sequence modulated spread spectrum signal that includes a sequence of carrier signals and a plurality of chips within a data bit time for each of a plurality of data bits;

generating a sequence of code words and a plurality of frequency sequence code words based on a predetermined relationship between the sequence of carrier signals and the plurality of chips, wherein the plurality of frequency sequence code words are generated as a function of the sequence code of words based upon the predetermined relationship, wherein predetermined relationship interrelates the plurality of frequency sequence code words to the sequence of code words;

generating a series of programmable carrier signals during each data bit time for each of the data bits in response to the plurality of frequency sequence code words through a programmable digital frequency synthesizer;

modulating each of the programmable carrier signals with the sequence code words to generate a fast frequency hopped local oscillator signal; and

mixing the fast frequency hopped direct sequence modulated spread spectrum signal with the fast frequency hopped local oscillator signal to down convert and despread the fast frequency hopped direct sequence modulated spread spectrum signal to generate a modulated data stream that contains the plurality of the data bits.

2. The method of claim 1, wherein mixing the fast frequency hopped direct sequence modulated spread spectrum signal with the fast frequency hopped local oscillator signal to down convert and despread the fast frequency hopped direct sequence modulated spread spectrum signal further comprises:

down converting and dispreading the fast frequency hopped direct sequence modulated spread spectrum signal simultaneously to generate the modulated data stream that contains the plurality of the data bits.

3. The method of claim 1, further comprising:

synchronizing the sequence of code words and the plurality of frequency sequence code words based upon detected reception timing of the plurality of chips, the sequence of carrier signals, or a combination of both.

4. The method of claim 1, wherein each of the data bits is represented by a plurality of sequences of chips, and each of the sequences of chips is transmitted on a respective carrier signal.

5. The method of claim 1, wherein generating the series of programmable carrier signals in response to the plurality of frequency sequence code words through the programmable digital frequency synthesizer further comprises:

sweeping the programmable digital frequency synthesizer.

6. The method of claim 1, wherein the-fast frequency hopped direct sequence modulated spread spectrum signal further includes a time hopped component;

and

wherein receiving the fast frequency hopped direct sequence modulated spread spectrum signal comprises;

generating a series of time gating code words; and

time gating the fast frequency hopped direct sequence modulated spread spectrum signal through a function of the series of time gating code words to remove the time hopped component.

7. The method of claim 6, wherein the predetermined relationship between the sequence of code words and the plurality of frequency sequence code words is a first predetermined relationship;

and

wherein the series of time gating code words is interrelated to the sequence of code words and the plurality of frequency sequence code words by a second predetermined relationship.

8. The method of claim 7, wherein the first predetermined relationship and the second predetermined relationship are based upon at least one of direct subsets, rolling code segments, scrambling of code vectors, and table-based reassignments of bit-pattern relationships, or a combination thereof.

9. The method of claim 6, wherein time gating the fast frequency hopped direct sequence modulated spread spectrum signal further comprising removing the time hopped component.

10. The method of claim 1, wherein the predetermined relationship that interrelates the sequence of code words and the plurality of frequency sequence code words is based upon at least one of direct subsets, rolling code segments, scrambling of code vectors, and table-based reassignments of bit-pattern relationships, or a combination thereof.

11. The method of claim 1, further comprising:

detecting a multipath condition based upon an envelope amplitude of the fast frequency hopped direct sequence modulated spread spectrum signal; and

in response to the detected multipath condition, performing a first order multipath cancellation process on the fast frequency hopped direct sequence modulated spread spectrum signal.

12. The method of claim 1, further comprising:

detecting a multipath condition based upon the fast frequency hopped direct sequence modulated spread spectrum signal;

generating a dynamic estimate of received-quality signal based upon the detected multipath condition; and

adaptively optimizing reception of the fast frequency hopped direct sequence modulated spread spectrum signal based upon the dynamic estimate of received-quality signal.

13. The method of claim 12, wherein adaptively optimizing reception of the fast frequency hopped direct sequence modulated special spectrum signal comprises:

optimizing a signal format of the fast frequency hopped direct sequence modulated spread spectrum signal at a point of transmission in response dynamically to the dynamic estimate.

14. The method of claim 1, wherein the fast frequency hopped direct sequence modulated spread spectrum signal is a first fast frequency hopped direct sequence modulated spread spectrum signal having a first polarization, and the plurality of data bits is a first plurality of data bits, the method further comprising:

receiving a second fast frequency hopped direct sequence modulated spread spectrum signal having a second polarization, wherein the second fast frequency hopped direct sequence modulated spread spectrum signal includes a sequence of carrier signals within the data bit time for each of a second plurality of data hits; and

mixing the second fast frequency hopped direct sequence modulated spread spectrum signal with the fast frequency hopped local oscillator signal to down convert and despread the second fast frequency hopped direct sequence modulated spread spectrum signal to generate a second modulated data stream that includes the second plurality of the data bits.

15. The method of claim 14, wherein mixing the second fast frequency hopped direct sequence modulated spread spectrum signal with the fast frequency hopped local oscillator signal further comprises:

balanced mixing the second fast frequency hopped direct sequence modulated spread spectrum signal with the fast frequency hopped local oscillator signal.

16. The method of claim 14, wherein mixing the second fast frequency hopped direct sequence modulated spread spectrum signal with the fast frequency hopped local oscillator signal to down convert and despread the second fast frequency hopped direct sequence modulated spread spectrum signal further comprises:

simultaneously down converting and dispreading the second fast frequency hopped direct sequence modulated spread spectrum signal to generate a second modulated data stream that includes the second plurality of the data bits.

17. The method of claim 16, further comprising:

combining the first modulated data stream and the second modulated data stream.

18. The method of claim 17, wherein combining the first modulated data stream and second modulated data stream further comprises:

summing, modifying, or gating the first modulated data stream and the second modulated data stream.

19. The method of claim 17, wherein combining the first modulated data stream and second modulated data stream further comprises:

feeding back a form of majority-logic directed signal to optimize the combination of the first modulated data stream and the second modulated data stream;

optimizing the combination of the first modulated data stream and the second modulated data stream through a function of the majority-logic directed signal.

20. The method of claim 16, wherein the first polarization and the second polarization are substantially linearly orthogonal.

21. The method of claim 20, wherein the first polarization and the second polarization are substantially vertically and horizontally polarized.

22. The method of claim 21, wherein the first Last frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal are spatially diverse.

23. The method of claim 16, further comprising:

detecting a multipath condition based upon the first modulated data stream and the second modulated data stream;

generating a dynamic estimate of received-quality signal based upon the detected multipath condition; and

optimizing reception of the first fast frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal adaptively based upon the dynamic estimate of received-quality signal.

24. The method of claim 23, wherein the optimizing reception of the first fast frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal comprises:

dynamically optimizing a signal format of the first fast frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal at a point of transmission in response to the dynamic estimate of received-quality signal.

25. The method of claim 24, wherein the signal format of the fast frequency hopped direct sequence modulated spread spectrum signal includes at least one of a direct sequence format, a fast hopping format, an amplitude dither, and a polarization parameter.

26. The method of claim 16, further comprising:

detecting a multipath condition based upon an envelope amplitude of at least one of the first fast frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal; and

performing a first order multipath cancellation process on the first fast frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal in response to the detected multipath condition.

27. The method of claim 16, wherein the first plurality of data bits and the second plurality of data bits are substantially identical.

28. The method of claim 1, wherein mixing the fast frequency hopped direct sequence modulated spread spectrum signal with the fast frequency hopped local oscillator signal to down convert and despread the fast frequency hopped direct sequence modulated spread spectrum signal to generate the modulated data stream that contains the plurality of the data bits further comprising:

mixing, with a balanced modulator, the fast frequency hopped direct sequence modulated spread spectrum signal with the fast frequency hopped local oscillator signal to down convert and despread the fast frequency hopped direct sequence modulated spread spectrum signal to generate a modulated data stream that contains the plurality of the data bits.

29. The method of claim 1, wherein modulating each of the programmable carrier signals with the direct sequence code words to generate the fast frequency hopped local oscillator signal further comprises:

modulating each of the programmable carrier signals with the direct sequence code words to generate a fast frequency hopped local oscillator signal with a balanced modulator.

30. A high multipath immunity receiver for receiving a plurality of data bits comprising:

a pseudo-random code generator configured to generate a stream of pseudo-random direct sequence code words;

the pseudo-random code generator further configured to generate an interrelated stream of pseudo-random local oscillator control code words as a function of the stream of pseudo-random direct sequence code words;

a programmable digital frequency synthesizer coupled to the pseudo-random code generator, the programmable digital frequency synthesizer configured to generate a pseudo-random sequence of local oscillator carrier frequencies during a data bit time for each of the data bits as a function of the interrelated pseudo-random local oscillator control word;

a modulator in communication with the pseudo-random code generator and the programmable digital frequency synthesizer, the modulator configured to generate a fast frequency hopped local oscillator signal as a function of the sequence of pseudo-random direct sequence code words and the sequence of local oscillator carrier frequencies; and

a mixer in communication with the modulator, wherein the mixer is configured to receive a fast frequency hopped direct sequence modulated spread spectrum signal, and further configured to despread and down covert the fast frequency hopped direct sequence modulated spread spectrum signal through a function of the fast frequency hopped local oscillator signal to generate a data modulated signal modulated with a single frequency signal.

31. The high multipath immunity receiver of claim 30, further comprising:

a demodulator coupled to the mixer, the demodulator configured to receive the data modulated signal modulated with a single frequency, the demodulator further configured to demodulate the received data modulated single frequency signal to recover data transmitted within the fast frequency hopped direct sequence modulated spread-spectrum signal.

32. The method of claim 30, wherein each of the data bits is represented by a plurality of sequences of chips, and each of the sequence of chips is transmitted on a respective carrier signal of the sequence of carrier signals.

34. The high multipath immunity receiver of claim 30, wherein the fast frequency hopped direct sequence modulated spread spectrum signal further includes a time hopped component, the receiver further comprising:

the pseudo-random code generator configured to generate a pseudo-random time gate control signal; and

an RF gate in communication with the mixer and the pseudo-random code generator, wherein in response to the pseudo-random time gate control signal, the RF gate is configured to remove a time hopped component of the fast frequency hopped direct sequence modulated spread spectrum signal to generate the fast frequency hopped direct sequence modulated spread spectrum signal without the time hopped component as a function of the pseudo-random time gate control signal.

35. The high multipath immunity receiver of claim 34, wherein the stream of pseudo-random direct sequence of code words are interrelated to the stream based upon at least one of of pseudo-random local oscillator code words based upon a first predetermined relationship;

and

wherein the pseudo-random time gate control signal is interrelated to the stream of pseudo-random direct sequence of code words and the stream of pseudo- random local oscillator control code words by a second predetermined relationship.

36. The high multipath immunity receiver of claim 35, wherein first predetermined relationship and the second predetermined relationship are based upon at least one of direct subsets of bits of the pseudo-random code generator, rolling code segments of the pseudo-random code generator, scrambling of code vectors of the pseudo-random code generator, and table-based reassignments of bit-pattern relationships of the pseudo-random code generator, or a combination thereof.

37. The high multipath immunity receiver of claim 34, wherein the RF gate toggles to pass the fast frequency hopped direct sequence modulated spread spectrum signal once during a period of each data bit time.

38. The high multipath immunity receiver of claim 30, wherein the predetermined relationship that interrelates the stream of pseudo-random direct sequence of code words and the stream of pseudo-random local oscillator control code words is based upon at least one of direct subsets of bits of the pseudo-random code generator, rolling code segments of the pseudo-random code generator, scrambling of code vectors of the pseudo-random code generator, and table-based reassignments of bit-pattern relationships of the pseudo-random code generator, or a combination thereof.

39. The high multipath immunity receiver of claim 30, further comprising:

a multipath condition detector in communication with the mixer, the multipath condition detector configured to generate a dynamic estimate of received-quality signal; and

a processor in communication with the multipath condition detector, the processor configured to adaptively optimize reception of the fast frequency hopped direct sequence modulated spread spectrum signal based upon the dynamic estimate of received-quality signal.

40. The high multipath immunity receiver of claim 39, further comprising:

a transmitter of the fast frequency hopped direct sequence modulated spread spectrum signal in communication with the high multipath immunity receiver, the transmitter configured to dynamically optimize a signal format of the fast frequency hopped direct sequence modulated spread spectrum signal in response to the dynamic estimate of received-quality signal.

41. The high multipath immunity receiver of claim 40, wherein the signal format of the fast frequency hopped direct sequence modulated spread spectrum signal includes at least one of a direct sequence format, a fast hopping format, an amplitude dither, and a polarization parameter.

56. The high multi-path immunity receiver of claim 30, wherein the modulator is configured as a balanced modulator.

57. The high multi-path immunity receiver of claim 30, wherein the modulator is a balanced modulator;

and

wherein the mixer is a balanced mixer.

33. A high multipath immunity receiver 30, wherein the programmable digital frequency synthesizer is further configured to frequency sweep a local carrier signal to generate the sequence of carrier frequencies.

42. The high multipath immunity receiver 30, wherein the fast frequency hopped direct sequence modulated spread spectrum signal is a first fast frequency hopped direct sequence modulated spread spectrum signal having a first polarization, the mixer is a first mixer, and the data modulated single frequency signal is a first data modulated single frequency signal;

the receiver further comprising;

a second mixer in communication with the modulator, wherein the mixer is configured to receive a second fast frequency hopped direct sequence modulated spread spectrum signal having a second polarization, and wherein the second mixer is further configured to despread and down covert the second fast frequency hopped direct sequence modulated spread spectrum signal through a function of the fast frequency hopped local oscillator signal to generate a second data modulated single frequency signal.

43. The high multipath immunity receiver of claim 42 further comprising:

a combiner circuit in communication with the first mixer and the second mixer that combines the first modulated data stream and second modulated data stream.

44. The high multipath immunity receiver of claim 43, wherein the combiner is configure to detect an amplitude of at least one of the first modulated data stream having a first polarized component and the second modulated data stream having a second polarized component.

45. The high multipath immunity receiver of claim 43, wherein the first polarized component and the second polarized component are combined through a combining function based upon at least one of gating, weighted summing, unweighted summing and, maximum ratio combining, or a combination thereof.

46. The high multipath immunity receiver of claim 43, further comprising a data demodulator in communication with the combiner circuit,

wherein the combiner circuit is configured to receive a feedback signal in a form of a majority-logic directed signal from the data demodulator to optimize the combination of the first modulated data stream and the second modulated data stream;

and

wherein the combiner circuit is configured to optimize the combination of the first modulated data stream and the second modulated data stream in response to the majority-logic directed signal.

47. The high multipath immunity receiver of claim 42, wherein the first polarization and the second polarization are substantially linearly orthogonal.

48. The high multipath immunity receiver of claim 47, wherein the first polarization and the second polarization are substantially vertically and horizontally polarized.

49. The high multipath immunity receiver of claim 42, wherein the first fast frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal are spatially diverse.

50. The high multipath immunity receiver of claim 42, further comprising:

a multipath detector in communication with the first mixer and the second mixer, the multipath detector configured to detect a multipath condition based upon an envelope amplitude of the fast frequency hopped direct sequence modulated spread spectrum signal; and

the high multipath immunity receiver further configured to perform a first order multipath cancellation process on the first fast frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal fast frequency hopped direct sequence modulated spread spectrum signal in response to the detected multipath condition.

51. The high multipath immunity receiver of claim 42, further comprising:

a multipath condition detector in communication with the first mixer and the second mixer, the multipath detector configured to receive the first modulated data stream and the second modulated data stream, and the multipath detector further configured to generate a dynamic estimate of received-quality signal based upon the first modulated data stream and the second modulated data stream; and

a processor in communication with the multipath condition detector, the processor configured to adaptively optimize reception of the fast frequency hopped direct sequence modulated spread spectrum signal.

52. The high multipath immunity receiver of claim 51, further comprising:

a transmitter of the first fast frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal in communication with the high multipath immunity receiver, the transmitter configured to dynamically optimize a signal format of the first fast frequency hopped direct sequence modulated spread spectrum signal and the second fast frequency hopped direct sequence modulated spread spectrum signal in response to the dynamic estimate of received-quality signal.

53. The high multipath immunity receiver of claim 52, wherein the signal format of the fast frequency hopped direct sequence modulated spread spectrum signal includes at least one of a direct sequence format, a fast hopping format, an amplitude dither, and a polarization parameter.

54. The high multi-path immunity receiver of claim 42, wherein the first mixer is a first balanced mixer.

55. The high multi-path immunity receiver of claim 42, wherein the first mixer is configured as a first balanced mixer;

and

wherein the second mixer is configured as a second balanced mixer.