Efficient apparatus for simultaneous modulation and digital beamforming for an antenna array

• US 5,909,460 A
• Filed: 12/07/1995
• Issued: 06/01/1999
• Est. Priority Date: 12/07/1995
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Dent, Paul W.
• Primary Examiner(s): VO, DON NGUYEN
• Application Number:
  US08/568,664
• Time in Patent Office: 1,272 Days
• Field of Search: 375/260, 375/308, 375/347, 375/200, 375/206, 342/354, 342/367, 342/368, 342/373, 342/374, 342/380, 342/383
• US Class Current: 375/130
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence

Abstract

A digital beamforming network for transmitting a first number of digital information signal using a second number of antenna array elements is disclosed. Assemblers are used for assembling one information bit selected from each of the information signals into a bit vector. Digital processors have an input for the bit vector and a number of outputs equal to the second number of antenna elements and process the bit vector. Finally, modulation waveform generators coupled to each of the second number of outputs generate a signal for transmission by each antenna element.

Claims

1. A digital beamforming network for transmitting a first number of digital information signals using a second number of antenna array elements, comprising:

means for assembling one information bit selected from each of said information signals into a bit vector;

digital processing means having an input for said bit vector and a number of outputs equal to said second number of antenna elements for processing said bit vector; and

modulation waveform generation means, coupled to each of said second number of outputs, for generating a signal for transmission by each antenna element.

2. The beamforming network according to claim 1, wherein said modulation generation means includes FIR filtering means using a set of FIR coefficients.

3. The beamforming network according to claim 2, wherein said coefficients form a square root of a Nyquist filter to an information signals data rate.

4. The beamforming network according to claim 1, wherein said modulation waveform generation means generates CDMA signals using a spreading code.

5. The beamforming network according to claim 1, wherein said modulation waveform generation means forms a filtered PSK signal.

6. The beamforming network according to claim 1, wherein said modulation waveform generation means forms a filtered QPSK signal.

7. The beamforming network according to claim 1, wherein said modulation waveform generation means forms a filtered Offset QPSK signal.

8. The beamforming network according to claim 1, wherein said modulation waveform generation means forms a filtered Pi/4-shifted QPSK signal.

9. The beamforming network according to claim 1, wherein said modulation waveform generation means forms a filtered DPSK signal.

10. The beamforming network according to claim 1, wherein said modulation waveform generation means forms a filtered DQPSK signal.

11. The beamforming network according to claim 1, wherein said modulation waveform generation means forms a filtered Offset DQPSK signal.

12. The beamforming network according to claim 1, wherein said modulation waveform generation means forms a filtered Pi/4-shifted DQPSK signal.

13. The beamforming network according to claim 1, wherein said modulation waveform generation means comprises Digital to Analog conversion.

14. The beamforming network according to claim 13, wherein said modulation waveform generation means comprises Quadrature Modulation.

15. The beamforming network according to claim 13, wherein said Digital-to-Analog conversion comprises high-bitrate Sigma-Delta Modulation.

16. The beamforming network according to claim 1, wherein said digital processing means comprises memory means to store precomputed look-up tables of partial sums of predetermined coefficients with arithmetic signs determined by bits of said input bit vector.

17. The beamforming network according to claim 16, wherein said partial sums are precomputed and stored for every combination of said bits of said bit vector.

18. The beamforming network according to claim 16 further comprising digital adders combine the outputs of more than one of said look-up tables.

19. The beamforming network according to claim 18, wherein digital adders are serial digital adders.

20. The beamforming network according to claim 19, wherein said look-up table values are stored with bits of increasing significance in successive memory word addresses, and different bits of said words represent bits of like significance from several of said precomputed values.

21. The beamforming network according to claim 16, wherein said memory means further stores values computed for more than one set of said coefficients.

22. The beamforming network according to claim 21, wherein values corresponding to a desired set of coefficients are selected from said memory by applying a channel address to said memory.

23. The beamforming network according to claim 22, wherein said channel address represents a timeslot of a TDMA frame.

24. The beamforming network according to claim 22, wherein said channel address represents a frequency channel.

25. The beamforming network according to claim 1, wherein said digital processing means has a further input for receiving a channel indicating signal.

26. The beamforming network according to claim 25, wherein said channel indicating signal represents a timeslot of a TDMA frame.

27. The beamforming network according to claim 25, wherein said channel indicating signal represents a frequency channel.

28. A digital beamforming network for transmitting a first times a second number of digital information signals using a third number of antenna array elements and said second number of communications channels, comprising:

means for assembling one information bit selected from each of a first said number of information signals for transmission on one of said second number of communications channels and assembling said selected bits into a bit vector;

digital processing means having an input for said bit vector and a number of outputs equal to said third number of antenna elements; and

modulation waveform generation means, coupled to each of said third number of outputs, for generating a signal for transmission by each antenna element on said one of said communications channels.

29. The beamforming network according to claim 28, wherein said assembling means successively assembles said bit vectors using information bits for transmission on successive communications channels and said digital processing means successively process said bit vectors to produce corresponding successive outputs.

30. The beamforming network according to claim 29, wherein said modulation waveform generation means further successively generates signals for transmission on successive communications channels using said successive outputs.

31. The beamforming network according to claim 28, wherein said communications channels are timeslots of a TDMA frame.

32. A digital beamformer for transmitting a first number of digital information streams using a second number of antenna array elements, comprising:

selection means for selecting one information bit from each of said information streams and assembling them to form a real bit vector and for selecting another information bit from said information streams to form an imaginary bit vector;

digital processing means for processing said real bit vector to obtain for each of said second number of antenna elements a first real and a first imaginary digital output word and to process said imaginary bit vector to obtain a corresponding number of second real and second imaginary output words;

combining means for combining for each antenna element its associated first real and second imaginary output words and to combine its associated first imaginary and second real output words to obtain a corresponding multi-bit QPSK modulation symbol; and

modulation waveform generation means for processing for each of said antenna elements said QPSK modulation symbols to obtain a corresponding QPSK-modulated radio waveform.

33. The beamformer according to claim 32, wherein said modulation generation means includes FIR filtering means using a set of FIR coefficients.

34. The beamformer according to claim 33, wherein said coefficients form a square root of a Nyquist filter to the symbol rate of said QPSK modulation symbols.

35. The beamformer according to claim 32, wherein said modulation waveform generation means comprises Quadrature Modulation.

36. The beamformer according to claim 32, wherein said modulation waveform generation means comprises Digital to Analog conversion.

37. The beamformer according to claim 36, wherein said Digital-to-Analog conversion comprises high-bitrate Sigma-Delta Modulation.

38. The beamformer according to claim 32, wherein said digital processing means comprises memory means to store precomputed look-up tables of partial sums of predetermined coefficients with arithmetic signs determined by bits of said input bit vector.

39. The beamformer according to claim 38, wherein said partial sums are precomputed and stored for every combination of said bits of said bit vector.

40. The beamformer according to claim 38, further comprising digital adders to combine the outputs of more than one of said look-up tables.

41. The beamformer according to claim 40, wherein said digital adders are serial digital adders.

42. The beamformer according to claim 41, wherein said look-up table values are stored with bits of increasing significance in successive memory word addresses, and different bits of said words represent bits of like significance from several of said precomputed values.

43. The beamformer according to claim 38, wherein said memory means further stores values computed for more than one set of said coefficients.

44. The beamformer according to claim 43, wherein values corresponding to a desired set of coefficients are selected from said memory by applying a channel address to said memory address inputs.

45. The beamformer according to claim 44, wherein said channel address represents a timeslot of a TDMA frame.

46. The beamformer according to claim 44, wherein said channel address represents a frequency channel.

47. The beamformer according to claim 32, wherein said digital processing means has a further input to receive a channel indicating signal.

48. The beamformer according to claim 47, wherein said channel indicating signal represents a timeslot of a TDMA frame.

49. The beamformer according to claim 47, wherein said channel indicating signal represents a frequency channel.

50. A digital beamformer for transmitting a first number of digital information streams using a second number of antenna array elements, comprising:

selection means for selecting one information bit at a time from each of said information streams and assembling them to form a real bit vector and for selecting another information bit from said information streams to form an imaginary bit vector in a repetitive sequence;

digital processing means for repetitively processing said real bit vectors alternately with said imaginary bit vectors to obtain for each of said second number of antenna elements a first real and a first imaginary digital output word related to each real bit vector and to obtain a corresponding number of second real and second imaginary output words related to each imaginary bit vector;

switching means for selecting first real digital output words alternating with said second imaginary output words to produce a stream of real OQPSK modulation values and for alternately selecting second real digital output words alternating with first imaginary output words to produce a stream of imaginary OQPSK modulation values; and

modulation waveform generation means for processing for each of said antenna elements said real and imaginary DQPSK modulation values to obtain a corresponding DQPSK-modulated radio waveform.

51. The beamformer according to claim 50, wherein said modulation waveform generation means includes FIR filtering means using a set of FIR coefficients.

52. The beamformer according to claim 51, wherein said coefficients form a square root of a Nyquist filter to the symbol rate of said OQPSK modulation symbols.

53. The beamformer according to claim 50, wherein said modulation waveform generation means comprises Quadrature Modulation.

54. The beamformer according to claim 50, wherein said modulation waveform generation means comprises Digital to Analog conversion.

55. The beamformer according to claim 54, wherein said Digital-to-Analog conversion comprises high-bitrate Sigma-Delta Modulation.

56. The beamformer according to claim 50, wherein said digital processing means comprises memory means to store precomputed look-up tables of partial sums of predetermined coefficients with arithmetic signs determined by bits of said input bit vector.

57. The beamformer according to claim 56, wherein said partial sums are precomputed and stored for every combination of said bits of said bit vector.

58. The beamformer according to claim 56 further comprising digital adders to combine the outputs of more than one of said look-up tables.

59. The beamformer according to claim 58, wherein said digital adders are serial digital adders.

60. The beamformer according to claim 59, wherein said look-up table values are stored with bits of increasing significance in successive memory word addresses, and different bits of said words represent bits of like significance from several of said precomputed values.

61. The beamformer according to claim 56, wherein said memory means further stores values computed for more than one set of said coefficients.

62. The beamformer according to claim 61, wherein values corresponding to a desired set of coefficients are selected from said memory by applying a channel address to said memory address inputs.

63. The beamformer according to claim 62, wherein said channel address represents a timeslot of a TDMA frame.

64. The beamformer according to claim 62, wherein said channel address represents a frequency channel.

65. The beamformer according to claim 50, wherein said digital processing means has a further input to receive a channel indicating signal.

66. The beamformer according to claim 65, wherein said channel indicating signal represents a timeslot of a TDMA frame.

67. The beamformer according to claim 65, wherein said channel indicating signal represents a frequency channel.