Array Antenna System and Spread Spectrum Beamformer Method

• US 20090103593A1
• Filed: 10/17/2008
• Published: 04/23/2009
• Est. Priority Date: 10/17/2007
• Status: Active Grant

• Current Assignee: Marcos Antonio Bergamo
• Original Assignee: Marcos Antonio Bergamo
• Inventors: Bergamo, Marcos Antonio
• Granted Patent: US 9,966,989 B2
• Time in Patent Office: Days
• US Class Current: 375/146
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/10 Code generation

Abstract

A method for transmitting digital beamformed signals in a transmit array antenna apparatus utilizing a single transceiver with one power amplifier, one up-frequency converter and one digital-to-analog converter for said array transmit antenna apparatus comprising the steps of: generating a first set of direct-sequence spread spectrum codes; generating a plurality of weights, each weight being a beamforming amplitude and phase or delay for each element; generating a direct-sequence spread spectrum multiplexed signal containing such weights while using one of such first-set codes per element; converting such an multiplexed signal to a convenient radio frequency; amplifying and transmitting such a multiplexed radio frequency signal to the elements; generating a second set of direct-sequence spread spectrum codes; extracting a radio frequency signal with direction-bearing weight information at each element while using a subset of codes from the second set; generating a third set of direct-sequence spread spectrum codes at each element; transmitting a signal with array gain beamformed towards a specific direction while using a transmit array apparatus composed of spaced elements, such a transmit beamformed signal being a radio frequency signal, a direct-sequence spread spectrum radio frequency signal containing a subset of codes from the third set, or a sequence of radio frequency pulses that have short duration and high power.

Claims

1. A method for transmitting digital beamformed signals in a transmit array antenna apparatus utilizing a single transceiver with one power amplifier, one up-frequency converter and one digital-to-analog converter for said array transmit antenna apparatus comprising the steps of:

generating a first set of direct-sequence spread spectrum codes;

generating a plurality of weights, each weight being a beamforming amplitude and phase or delay for each element;

generating a direct-sequence spread spectrum multiplexed signal containing such weights while using one of such first-set codes per element;

converting such an multiplexed signal to a convenient radio frequency;

amplifying and transmitting such a multiplexed radio frequency signal to the elements;

generating a second set of direct-sequence spread spectrum codes;

extracting a radio frequency signal with direction-bearing weight information at each element while using a subset of codes from the second set;

generating a third set of direct-sequence spread spectrum codes at each element;

transmitting a signal with array gain beamformed towards a specific direction while using a transmit array apparatus composed of spaced elements, such a transmit beamformed signal being a radio frequency signal, a direct-sequence spread spectrum radio frequency signal containing a subset of codes from the third set, or a sequence of radio frequency pulses that have short duration and high power.

3. The method of claim 1, wherein each code of the first-set codes is a row of a circulant matrix.

4. The method of claim 1, wherein each row of the circulant matrix is a cyclic shift of a common maximal-length sequence.

5. The method of claim 1, wherein each code of the first set is a scaled version of a row of a circulant matrix.

6. The method of claim 1, wherein the at least one code of the first set is orthogonal to at least one code of the second set.

7. The method of claim 1, wherein codes from different rows of first and second sets are mutually orthogonal.

8. The method of claims 1, 4 and 7, wherein codes of first set have values ±

1 and each code of the second set is obtained from a corresponding row from the first set by replacing the negative values (i.e., −

1) by zeros.

9. The method of claim 1, wherein the transmitting step includes the sub-steps of:

modulating the information using a first modulation;

combining the modulated information with one of the codes of the first set;

converting the modulated information combined with the codes in a multi-level aggregate baseband signal, up-converting the baseband signal to a radio frequency signal, power-amplifying the radio frequency signal, and sending the amplified aggregate radio frequency signal to a subset including all elements of the array.

10. The method of claim 9, wherein the first modulation is M-ary Phase-Shift Keying or PSK, including Binary Phase Shift Keying or BPSK.

11. The method of claim 9, wherein the first modulation is M-ary Quadrature Amplitude Modulation or QAM including Quadrature-Phase Shift Keying or QPSK and Offset Quadrature-Phase Shift Keying or OQPSK.

12. The method of claim 9, wherein the modulated symbol has an arbitrary complex value.

13. The method of claim 12, wherein the complex values assigned to codes with consecutive cyclic shifts results from discrete time signal including samples from a continuous time signal including samples from a sensor device or system.

14. The method of claim 12, wherein the complex values assigned to codes with consecutive cyclic shifts has a specified timing or spectral characteristic including radar signals with specified time and frequency resolution.

15. The method of claims 1 and 9, wherein the sending of the aggregate radio frequency signal to the elements includes wireless and wired means.

16. The method of claim 1, wherein the radio frequency signal for each element is extracted from the aggregate radio frequency signal transmitted to all the elements by correlating it against codes of the second set.

17. The method of claims 1 and 16, wherein the correlation is implemented at each element by multiplying or re-modulating the aggregate signal with one or a sub-set of codes from the second set followed by filtering the resulting radio frequency signal by a narrow high-Q band-pass filter centered at the carrier frequency for the array.

18. The method of claims 1 and 17, wherein the filtered radio frequency signal is sent to and transmitted by the antenna element without further re-modulation or conditioning.

19. The method of claims 1 and 17, wherein the filtered radio frequency signal is re-modulated using one or a subset of codes from the third set, and then sent to and transmitted by the antenna element as a radio frequency spread spectrum signal.

20. The method of claims 1, 18 and 19, wherein the resulting radio frequency signal (i.e., ‘

as is’

or spread spectrum) is segmented in wave-blocks and each wave-block is compressed and transmitted as a radio frequency pulse.

21. The method of claims 1, 19 and 20, wherein a wave-block corresponds to one or a fraction of a chip of the spread spectrum signal.

22. The method of claims 1 and 20, wherein compression of a wave-block in a pulse is accomplished through coherent accumulation of segments of such a wave-block, each segment corresponding to a specified number of integer cycles at the carrier frequency for the array.

23. The method of claims 1 and 22, wherein pulse power amplification results from incremental and recurring coherent energy accumulation as the radio frequency signal propagates over a delay line.

24. The method of claims 1, 22 and 23, wherein the number of cycles per pulse is determined by the length of such delay line.

25. The method of claims 1, 22 and 23, wherein the power amplification of the radio frequency pulse is determined by the relative lengths of the wave-block and delay line.

26. The method of claims 1, 22 and 23, wherein the coherent power amplification is implement as in FIG. 16 using just passive components not including capacitors or inductances.

27. The method of claims 1, 19 and 20, wherein the radio frequency signal transmitted beamformed in the direction of a receiver array is a direct-sequence spread spectrum radio frequency signal containing one or a subset of codes with reflective properties compatible with the receive beamforming methods included in this invention, including spread spectrum signals in which each chip is transmitted as one or a set of short-duration pulses.

2. A method for receiving direct-sequence spread spectrum signals containing a plurality of codes with digital beamforming in a receive array antenna apparatus utilizing a single transceiver with one low noise amplifier, one down-frequency converter and one analog-to-digital converter for said receive array antenna apparatus comprising the steps of:

receiving a subset of codes of said direct-sequence spread spectrum signals from multiple positions or from one or multiple transmitters located at different positions while using a receive array apparatus composed of spaced-elements;

reflecting such received signals at each element;

combining such reflected signals forming a common aggregated signal for the array;

converting such an aggregate signal to a convenient intermediary frequency including baseband;

sampling such a frequency-converted signal;

correlating resulting samples against codes or variations of such codes included in the reflected signals;

demultiplexing the reflected signals;

detecting direction-bearing parameters included in such demultiplexed signals including joint detection of such parameters and data included in the incident signals,

generating a receive beamformed signal towards one or more selected directions included or not in such direction-bearing parameters, such a receive beamformed signal being a baseband signal with receive array gain towards such selected directions.

28. The method of claim 2 and 27, wherein each code included in the spread spectrum radio frequency signal incident in the receive array is a row of a circulant matrix.

29. The method of claims 2 and 28, wherein each row of the circulant matrix is a different cyclic-shift of a common maximal-length sequence.

30. The method of claims 2, 27 and 28, wherein each code of the incident radio frequency spread spectrum signal is a scaled version of a row of a circulant matrix.

31. The method of claims 2, 27 and 28, wherein the signal incident on the array includes a plurality of spread spectrum signals.

32. The method of claim 2, 27 and 28, wherein the signal incident on the array includes signals from a plurality of transmitters at difference locations.

33. The method of claim 2 and 31, wherein at least one of the incident signals from at least one of the transmitters includes multipath reflections from urban structures such as mountains and buildings.

34. The method of claim 2, 31 and 32, wherein at least one of the incident signals from at least one of the transmitter include reflections, including multipath reflections from a plurality of stationary or moving objects such as airplanes.

35. The method of claim 2, wherein the reflecting signal of each element have distinguishable spectrum features including distinguishable amplitudes and delays.

36. The method of claims 2, 28 and 35, wherein the reflecting signal is includes a row of the circulant matrix.

37. The methods of claims 2, 28, 29 and 35, wherein the reflecting signal is circulating and does not include a maximal-length sequence included in the received signals.

38. The method of claim 2, wherein the reflected signal by each element results from the multiplication or re-modulation of the incident signal at each element by the reflecting signal at such an element.

39. The methods or claims 2 and 38, wherein the reflected signals are combined using a cable.

40. The methods of claims 2 and 38, wherein the reflected signals are combined using a microwave signal combiner including a Wilkinson combiner.

41. The methods of claims 2 and 38, wherein the reflected signals propagate away from the antenna elements through backscattering and combine wirelessly at a location remote from the receive elements.

42. The method of claims 2 and 38, wherein the reflected signal at each element result from an impedance mismatch between the antenna element and the load circuit.

43. The method of claim 42, wherein the reflecting signal at each element controls the impedance of such a load.

44. The method of claims 2 and 38, wherein the reflected signals are generated using surface acoustic wave (SAW) devices.

45. The method of claim 2, wherein a single digital receiver for the entire array is used to used to amplify down-convert and sample the aggregate signal resulting from the combination of reflected signals.

46. The methods of claims 2, 38 and 45, wherein the reflecting signals are synchronized with the sample-and-hold devices included in the analog-to-digital converter such that sampling is performed half-way between consecutive transitions included in the reflecting signals as the resulting reflected signal are received at the analog-to-digital converter.

47. The methods of claims 2 and 45, wherein the analog-to-digital converter operates at least at the Nyquist frequency of the aggregate signal resulting from the reflected signals while producing at least one complex-valued sample per chip time.

48. The method of claim 2, wherein a correlator apparatus including software operations are used to demultiplex and detect beamforming-bearing information for each element and included in the aggregate signal that result from the combination of reflected signals.

49. The methods of claims 2, 29 and 48, wherein the codes used in the correlation are derived from maximal length sequences included in the incident signals.

50. The methods of claims 2 and 49, wherein the correlation is performed using select and add operations.

51. The methods of claims 2, 48 and 49, wherein the correlation results from selecting just the sample positions corresponding to positive values of such cyclically shifted maximal length sequences.

52. The method of claims 2 and 48, wherein direction-bearing information detected from at least one of the incident signals are used in the beamforming operations for isolating or nulling such at least one of the signals.

53. The method of claim 2, wherein weights that include information of one, a set or all the incident angles are used in the beamforming operations for separating signals incident at different angles.

54. The methods of claims 2, 52 and 53, wherein the beamforming operations include forming nulls toward one or a set of specified angular directions, including directions of at least one of the incident signals.

55. The methods of claims 2, 52, 53 and 54, wherein the beamforming operations include joint detection of modulated symbols, complex-valued samples, complex-valued data and multipath-bearing information included in the incident signals.