High data rate spread spectrum transceiver and associated methods

• US 5,982,807 A
• Filed: 03/17/1997
• Issued: 11/09/1999
• Est. Priority Date: 03/17/1997
• Status: Expired

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Snell, James Leroy
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GHAYOUR, MOHAMMAD H
• Application Number:
  US08/819,846
• Time in Patent Office: 967 Days
• Field of Search: 375/200, 375/205, 375/206, 375/208, 375/209, 375/210, 375/279, 375/280
• US Class Current: 375/146
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04J 13/0048 Walsh
• CPC Class Codes: H04J 13/12 Generation of orthogonal codes
• CPC Class Codes: H04L 27/18 Phase-modulated carrier systems, i.e. using phase-shift keying H04L27/32 takes precedence

Abstract

A spread spectrum radio transceiver includes a high data rate baseband processor and a radio circuit connected thereto. The baseband processor preferably includes a modulator for spread spectrum phase shift keying (PSK) modulating information for transmission via the radio circuit. The modulator may include at least one modified Walsh code function encoder for encoding information according to a modified Walsh code for substantially reducing an average DC signal component to thereby enhance overall system performance when AC-coupling the received signal through at least one analog-to-digital converter to the demodulator. The demodulator is for spread spectrum PSK demodulating information received from the radio circuit. The modulator and demodulator are each preferably operable in one of a bi-phase PSK (BPSK) mode at a first data rate and a quadrature PSK (QPSK) mode at a second data rate. These formats may also be switched on-the-fly in the demodulator. Method aspects are also disclosed.

Claims

1. A spread spectrum radio transceiver comprising:

a baseband processor and a radio circuit connected thereto, said baseband processor comprising

a demodulator for spread spectrum phase shift keying (PSK) demodulating information received from said radio circuit,

at least one analog-to-digital (A/D) converter having an output connected to said demodulator and an input AC-coupled to said radio circuit,

said demodulator comprising at least one modified Walsh code function correlator for decoding information according to a modified Walsh code reducing an average DC signal component which in combination with the AC-coupling to said at least one A/D converter enhances overall performance, and

a modulator for spread spectrum PSK modulating information for transmission via the radio circuit, said modulator comprising at least one modified Walsh code function encoder for encoding information according to the modified Walsh code.

2. A spread spectrum radio transceiver according to claim 1 wherein said modulator comprises means for operating in one of first format defined by bi-phase PSK (BPSK) modulation at a first data rate and a second format defined by quadrature PSK (QPSK) modulation at a second data rate;

and wherein said demodulator comprises means for operating in one of the first and second formats.

3. A spread spectrum radio transceiver according to claim 2 wherein said modulator comprises header modulator means for modulating data packets to include a header at a third format defined by a predetermined modulation at a third data rate and variable data in one of the first and second formats;

and wherein said demodulator comprises header demodulator means for demodulating data packets by demodulating the header at the third format and for switching to the respective one of the first and second formats of the variable data after the header.

4. A spread spectrum radio transceiver according to claim 3 wherein the predetermined modulation of the third format is differential BPSK (DBPSK), and wherein the third data rate is lower than the first and second data rates.

5. A spread spectrum radio transceiver according to claim 3 wherein said demodulator further comprises:

a first carrier tracking loop for the third format; and

a second carrier tracking loop for the first and second formats.

6. A spread spectrum radio transceiver according to claim 5 wherein said second carrier tracking loop comprises:

a carrier numerically controlled oscillator (NCO); and

carrier NCO control means for selectively operating said carrier NCO based upon a carrier phase of said first carrier tracking loop to thereby facilitate switching to the format of the variable data.

7. A spread spectrum radio transceiver according to claim 5 wherein said second carrier tracking loop comprises:

a carrier loop filter; and

carrier loop filter control means for selectively operating said carrier loop filter based upon a frequency of said first carrier tracking loop to thereby facilitate switching to the format of the variable data.

8. A spread spectrum radio transceiver according to claim 1 wherein said modulator further comprises means for partitioning data into four bit nibbles of sign (one bit) and magnitude (three bits) to said at least one modified Walsh code function encoder.

9. A spread spectrum radio transceiver according to claim 1 wherein the modified Walsh code is a Walsh code modified by a modulo two addition of a fixed hexadecimal code thereto.

10. A spread spectrum radio transceiver according to claim 1 wherein said at least one modified Walsh code function correlator comprises:

a modified Walsh function generator; and

a plurality of parallel connected correlators connected to said modified Walsh function generator.

11. A spread spectrum radio transceiver according to claim 1 wherein said modulator comprises spreading means for spreading each data bit using a pseudorandom (PN) sequence at a predetermined chip rate and preamble modulating means for generating a preamble;

and wherein said demodulator comprises preamble demodulator means for demodulating the preamble for achieving initial PN sequence synchronization.

12. A spread spectrum radio transceiver according to claim 1 wherein said modulator comprises a scrambler;

and wherein said demodulator comprises a descrambler.

13. A spread spectrum radio transceiver according to claim 1 wherein said demodulator comprises clear channel assessing means for generating a clear channel assessment signal.

14. A spread spectrum radio transceiver according to claim 1 wherein said radio circuit comprises:

a quadrature intermediate frequency modulator/demodulator connected to said baseband processor; and

an up/down frequency converter connected to said quadrature intermediate frequency modulator/demodulator.

15. A spread spectrum radio transceiver according to claim 14 wherein said radio circuit further comprises:

a low noise amplifier having an output connected to an input of said up/down converter; and

a radio frequency power amplifier having an input connected to an output of said up/down converter.

16. A spread spectrum radio transceiver according to claim 15 further comprising:

an antenna; and

an antenna switch for switching said antenna between the output of said radio frequency power amplifier and the input of said low noise amplifier.

17. A baseband processor for a spread spectrum radio transceiver, said baseband processor comprising:

a demodulator for spread spectrum phase shift keying (PSK) demodulating;

at least one analog-to-digital (A/D) converter having an output connected to said demodulator and an input AC-coupled to receive information;

said demodulator comprising at least one predetermined orthogonal code function correlator for decoding information according to a predetermined orthogonal code reducing an average DC signal component to thereby increase AC-coupling to said at least one A/D converter; and

a modulator for spread spectrum PSK modulating information for transmission, said modulator comprising at least one predetermined orthogonal code function encoder for encoding information according to the predetermined orthogonal code.

18. A baseband processor according to claim 17 wherein said modulator comprises means for operating in one of first format defined by bi-phase PSK (BPSK) modulation at a first data rate and a second format defined by quadrature PSK (QPSK) modulation at a second data rate;

and wherein said demodulator comprises means for operating in one of the first and second formats.

19. A baseband processor according to claim 18 wherein said modulator comprises header modulator means for modulating data packets to include a header at a third format defined by a predetermined modulation at a third data rate and variable data in one of the first and second formats;

and wherein said demodulator comprises header demodulator means for demodulating data packets by demodulating the header at the third format and for switching to the respective one of the first and second formats of the variable data after the header.

20. A baseband processor according to claim 19 wherein the predetermined modulation of the third format is differential BPSK (DBPSK), and wherein the third data rate is lower than the first and second data rates.

21. A baseband processor according to claim 19 wherein said demodulator further comprises:

a first carrier tracking loop for the third format; and

a second carrier tracking loop for the first and second formats.

22. A baseband processor according to claim 21 wherein said second carrier tracking loop comprises:

a carrier numerically controlled oscillator (NCO); and

carrier NCO control means for selectively operating said carrier NCO based upon a carrier phase of said first carrier tracking loop to thereby facilitate switching to the format of the variable data.

23. A baseband processor according to claim 21 wherein said second carrier tracking loop comprises:

a carrier loop filter; and

carrier loop filter control means for selectively operating said carrier loop filter based upon a frequency of said first carrier tracking loop to thereby facilitate switching to the format of the variable data.

24. A baseband processor according to claim 17 wherein said modulator further comprises means for partitioning data into four bit nibbles of sign (one bit) and magnitude (three bits) to said at least one predetermined orthogonal code function encoder.

25. A baseband processor according to claim 17 wherein the predetermined orthogonal code is a Walsh code modified by a modulo two addition of a fixed hexadecimal code thereto.

26. A baseband processor according to claim 17 wherein the predetermined orthogonal code is a bi-orthogonal code.

27. A baseband processor according to claim 17 wherein said at least one predetermined orthogonal code function correlator comprises:

a predetermined orthogonal code function generator; and

a plurality of parallel connected correlators connected to said predetermined orthogonal code function generator.

28. A baseband processor according to claim 17 wherein said modulator comprises spreading means for spreading each data bit using a pseudorandom (PN) sequence at a predetermined chip rate and preamble modulating means for generating a preamble;

and wherein said demodulator comprises preamble demodulator means for demodulating the preamble for achieving initial PN sequence synchronization.

29. A baseband processor according to claim 17 wherein said modulator comprises a scrambler;

and wherein said demodulator comprises a descrambler.

30. A baseband processor for a spread spectrum radio transceiver, said baseband processor comprising:

a modulator for spread spectrum phase shift keying (PSK) modulating information for transmission, said modulator comprising

at least one encoder for encoding information for transmission,

means for operating in one of a first format defined by bi-phase PSK (BPSK) modulation at a first data rate and a second format defined by quadrature PSK (QPSK) modulation at a second data rate,

header modulator means for modulating data packets to include a header at a third format defined by a predetermined modulation at a third data rate and variable data in one of the first and second formats; and

a demodulator for spread spectrum PSK demodulating received information, said demodulator comprising

at least one correlator for decoding received information,

means for operating in one of the first and second formats,

header demodulator means for demodulating data packets by demodulating the header at the third format and for switching to the respective one of the first and second formats of the variable data after the header,

a first carrier tracking loop for the third format, and

a second carrier tracking loop for the first and second formats.

31. A baseband processor according to claim 30 wherein the predetermined modulation of the third format is differential BPSK (DBPSK), and wherein the third data rate is lower than the first and second data rates.

32. A baseband processor according to claim 30 wherein said second carrier tracking loop comprises:

a carrier numerically controlled oscillator (NCO); and

carrier NCO control means for selectively operating said carrier NCO based upon a carrier phase of said first carrier tracking loop to thereby facilitate switching to the format of the variable data.

33. A baseband processor according to claim 30 wherein said second carrier tracking loop comprises:

a carrier loop filter; and

carrier loop filter control means for selectively operating said carrier loop filter based upon a frequency of said first carrier tracking loop to thereby facilitate switching to the format of the variable data.

34. A baseband processor according to claim 30 wherein said modulator comprises spreading means for spreading each data bit using a pseudorandom (PN) sequence at a predetermined chip rate and preamble modulating means for generating a preamble;

and wherein said demodulator comprises preamble demodulator means for demodulating the preamble for achieving initial PN sequence synchronization.

35. A baseband processor according to claim 30 wherein said modulator comprises a scrambler;

and wherein said demodulator comprises a descrambler.

36. A modulator for a spread spectrum radio transceiver, said modulator comprising:

modulator means for spread spectrum phase shift keying (PSK) modulating information for transmission, said modulator means comprising at least one predetermined orthogonal code function encoder for encoding information according to a predetermined orthogonal code for reducing an average DC signal component.

37. A modulator according to claim 36 wherein said modulator means comprises means for operating in one of first format defined by bi-phase PSK (BPSK) modulation at a first data rate and a second format defined by quadrature PSK (QPSK) modulation at a second data rate.

38. A modulator according to claim 37 wherein said modulator means comprises header modulator means for modulating data packets to include a header at a third format defined by a predetermined modulation at a third data rate and variable data in one of the first and second formats.

39. A modulator according to claim 38 wherein the predetermined modulation of the third format is differential BPSK (DBPSK), and wherein the third data rate is lower than the first and second data rates.

40. A modulator according to claim 36 wherein said modulator means further comprises means for partitioning data into four bit nibbles of sign (one bit) and magnitude (three bits) to said at least one predetermined orthogonal code function encoder, and wherein the predetermined orthogonal code is a Walsh code modified by a modulo two addition of a fixed hexadecimal code thereto.

41. A modulator according to claim 36 wherein said at least one predetermined orthogonal code function correlator comprises:

a predetermined orthogonal code function generator; and

a plurality of parallel connected correlators connected to said predetermined orthogonal code function generator.

42. A modulator according to claim 36 wherein the predetermined orthogonal code is a Walsh code modified by a modulo two addition of a fixed hexadecimal code thereto.

43. A modulator according to claim 36 wherein the predetermined orthogonal code is a bi-orthogonal code.

44. A demodulator for a spread spectrum radio transceiver, said demodulator comprising:

demodulator means for spread spectrum phase shift keying (PSK) demodulating information received from said radio circuit, said demodulator means comprising at least one predetermined orthogonal code function correlator for decoding information according to a predetermined orthogonal code reducing an average DC signal component.

45. A demodulator according to claim 44 wherein said demodulator means comprises means for operating in one of first format defined by bi-phase PSK (BPSK) modulation at a first data rate and a second format defined by quadrature PSK (QPSK) modulation at a second data rate.

46. A demodulator according to claim 45 wherein said demodulator means comprises header demodulator means for demodulating data packets including a header in a third format defined by a predetermined modulation at a third data rate and variable data in one of the first and second formats, and for switching to the respective one of the first and second formats of the variable data after the header.

47. A demodulator according to claim 46 wherein the predetermined modulation of the third format is differential BPSK (DBPSK), and wherein the third data rate is lower than the first and second data rates.

48. A demodulator according to claim 46 wherein said demodulator means further comprises:

a first carrier tracking loop for the third format; and

a second carrier tracking loop for the first and second formats.

49. A demodulator according to claim 48 wherein said second carrier tracking loop comprises:

a carrier numerically controlled oscillator (NCO); and

carrier NCO control means for selectively operating said carrier NCO based upon a carrier phase of said first carrier tracking loop to thereby facilitate switching to the format of the variable data.

50. A demodulator according to claim 48 wherein said second carrier tracking loop comprises:

a carrier loop filter; and

carrier loop filter control means for selectively operating said carrier loop filter based upon a frequency of said first carrier tracking loop to thereby facilitate switching to the format of the variable data.

51. A demodulator according to claim 44 further comprising means for partitioning data into four bit nibbles of sign (one bit) and magnitude (three bits).

52. A demodulator according to claim 44 wherein the predetermined orthogonal code is a Walsh code modified by a modulo two addition of a fixed hexadecimal code thereto.

53. A demodulator according to claim 44 wherein the predetermined orthogonal code is a bi-orthogonal code.

54. A demodulator according to claim 44 wherein said at least one predetermined orthogonal code function correlator comprises:

a predetermined orthogonal code function generator; and

a plurality of parallel connected correlators connected to said predetermined orthogonal code function generator.

55. A method for baseband processor for spread spectrum radio communication, the method comprising the steps of:

spread spectrum phase shift keying (PSK) modulating information for transmission while encoding the information according to the predetermined orthogonal code for reducing an average DC signal component; and

spread spectrum PSK demodulating received information by decoding the received information according to the predetermined orthogonal code.

56. A method according to claim 55 further comprising the step of AC-coupling received information for spread spectrum PSK demodulating so that the reduced average DC signal component in combination with the AC-coupling enhances overall performance.

57. A method according to claim 55 further comprising the steps of modulating and demodulating in one of first format defined by bi-phase PSK (BPSK) modulation at a first data rate and a second format defined by quadrature PSK (QPSK) modulation at a second data rate.

58. A method according to claim 57 further comprising the steps of:

modulating data packets to include a header at a third format defined by a predetermined modulation at a third data rate and variable data in one of the first and second formats; and

demodulating data packets by demodulating the header at the third format and for switching to the respective one of the first and second formats of the variable data after the header.

59. A method according to claim 58 wherein the predetermined modulation of the third format is differential BPSK (DBPSK), and wherein the third data rate is lower than the first and second data rates.

60. A method according to claim 55 wherein the predetermined orthogonal code is a Walsh code modified by a modulo two addition of a fixed hexadecimal code thereto.

61. A method according to claim 55 wherein the predetermined orthogonal code is a bi-orthogonal code.