Multi-dimensional real-array radar antennas and systems steered and focused using fast fourier transforms

• US 7,504,985 B2
• Filed: 11/16/2006
• Issued: 03/17/2009
• Est. Priority Date: 11/17/2005
• Status: Expired due to Fees

• Current Assignee: Board of Regents Nevada System of Higher Education (State of Nevada)
• Original Assignee: Board of Regents Nevada System of Higher Education (State of Nevada)
• Inventors: Kohlmoos, Ross P., Henson, James M.
• Primary Examiner(s): Sotomayor; John B
• Application Number:
  US11/601,322
• Publication Number:
  US 20070132631A1
• Time in Patent Office: 852 Days
• Field of Search: 342/25.R, 342 25 A- 25 F, 342/179, 342/180, 342190-197
• US Class Current: 342/25.00R
• CPC Class Codes: G01S 13/89 for mapping or imaging

Abstract

Radar systems are disclosed that include a signal generator, an antenna, a switching circuit, an I/Q sampling and signal-demodulation (demodulation) processor, and a FFT processor. The signal generator produces energization signals. The antenna has multiple individual antenna elements. The switching circuit is configured to deliver the energization signals to a selected antenna element at a respective moment in time to cause the selected antenna element to transmit a respective radar signal in response to the energization signal. At least one element receives a corresponding return-radar signal before the switching circuit selects a next antenna element to transmit a respective radar signal. The demodulation processor receives the return-radar signals from the antenna elements and demodulates the return-radar signals. The FFT processor fast-Fourier transforms the return-radar signals. The system can include a magnitude processor that determines, from the Fourier transforms, respective magnitudes of the return signals in at least one data plane. The system also can include an imager.

Claims

1. A radar system, comprising:

a signal generator configured to produce energization signals;

an antenna comprising an array of multiple antenna elements;

a switching circuit connected to the signal generator and to the antenna and configured to deliver the energization signals to a selected individual antenna element at a respective moment in time to cause the selected antenna element to transmit a respective radar signal in response to the respective energization signal, wherein at least the respective selected antenna element receives a corresponding return-radar signal before the switching circuit selects a next antenna element to transmit a respective radar signal;

an I/Q sampling and signal-demodulation processor connected so as to receive the return-radar signals from the antenna elements and configured to demodulate the return-radar signals; and

a fast Fourier-transform (FFT) processor connected to the I/Q sampling and signal-demodulation processor and configured to perform fast Fourier transforms of the return-radar signals.

2. The system of claim 1, wherein the corresponding return-radar signal is received by substantially all the antenna elements of the array.

3. The system of claim 1, wherein the next antenna element is different from the selected antenna element.

4. The system of claim 3, wherein the next antenna element is next in a predetermined sequence of elements.

5. The system of claim 3, wherein the switching circuit is further configured to allow the corresponding return-radar signal to be received by multiple antenna elements of the array before an energization signal is sent to the next antenna element.

6. The system of claim 1, wherein:

the next antenna element is the same as the selected antenna element; and

the switching circuit is configured to send respective energization signals to the same antenna element at respective moments in time.

7. The system of claim 6, wherein the switching circuit is further configured to allow the corresponding return-radar signal to be received by multiple antenna elements of the array before a subsequent energization signal is sent to the same antenna element.

8. The system of claim 1, further comprising a magnitude processor connected to the FFT processor and configured to determine, from the Fourier transforms, respective magnitudes of the return-radar signals in at least one respective data plane.

9. The system of claim 8, wherein the magnitude processor is configured to determine, from the Fourier transforms, respective magnitudes of the return-radar signals in multiple respective data planes.

10. The system of claim 1, wherein the switching circuit is configured to deliver energization signals one at time in an ordered manner to energize the antenna elements and cause them to transmit their respective radar signals at respective moments in time.

11. The system of claim 10, wherein the switching circuit is configured to energize the antenna elements in the array in a sequential manner.

12. The system of claim 1, wherein a respective return-radar signal is received by an energized antenna element before a next antenna element of the array receives a respective energization signal from the switching circuit.

13. The system of claim 1, wherein the array of elements of the antenna is one-dimensional.

14. The system of claim 1, wherein the array of elements of the antenna is multi-dimensional.

15. The system of claim 1, wherein each antenna element is a respective dipole radiator having a relatively wide half-power beamwidth.

16. The system of claim 1, wherein the I/Q sampling and signal-demodulation processor is configured:

to produce, from the respective return-radar signals received by the antenna elements, respective I and Q range-resolved signals; and

to sort the I and Q range-resolved signals into range bins to form a set of complex iso-range data planes each holding respective complex (I/Q) received data values at the respective range.

17. The system of claim 16, wherein the FFT processor is configured:

to receive the iso-range complex-data planes; and

to perform a two-dimensional fast-Fourier transform of the respective data values in the received complex-data planes.

18. The system of claim 17, wherein the FFT processor is further configured to use, while performing the fast-Fourier transforms, “

I”

data values as corresponding “

real”

input portions, and “

Q”

data values as corresponding “

imaginary”

input portions.

19. The system of claim 18, wherein the FFT processor is further configured to produce, for each complex input value, a corresponding complex output value having a magnitude formed as a square root of a sum of squared real and imaginary values, thereby producing two-dimensional planes of output data, one respective plane for each range.

20. The system of claim 19, further comprising a magnitude processor connected to the Fourier-transform processor, the magnitude processor being configured to determine, from the Fourier transforms, respective magnitudes of the return-radar signals in at least one respective data plane.

21. The system of claim 20, further comprising an imager connected to the magnitude processor, the imager being configured to receive at least one data plane from the magnitude processor and to produce therefrom a multi-dimensional image.

22. The system of claim 21, further comprising an imager connected to the magnitude processor, the imager being configured to receive multiple planes of output data and to produce a three-dimensional image from said data.

23. A radar system, comprising:

antenna means for transmitting radar signals and for receiving returning radar signals, the antenna means comprising an array of multiple antenna elements;

signal-generation means for producing antenna-element-energization signals;

switching means for delivering the energization signals to a selected individual antenna element at a respective moment in time to cause the selected antenna element to transmit a respective radar signal in response to the respective energization signals and at least the respective selected element to receive a corresponding return-radar signal;

signal-sampling means for demodulating the respective return-radar signals received by the antenna elements; and

processor means for performing Fourier transforms of the return-radar signals.

24. The system of claim 23, further comprising magnitude-processing means for receiving the Fourier transforms and for determining, from the Fourier transforms, respective magnitudes of the return-radar signals in at least one respective data plane.

25. The system of claim 23, further comprising magnitude-processor means for determining, from the Fourier transforms, respective magnitudes of the return signals in at least one respective data plane.

26. The system of claim 25, further comprising imaging means for receiving at least one data plane and for producing an image from the at least one data plane.

27. A method for performing radar, comprising:

generating a series of respective energization signals at different respective moments in time;

delivering the energization signals selectively to individual respective antenna elements in an array of such elements to cause the energized antenna elements to transmit the respective radar signals at the respective moments in time;

receiving return-radar signals by one or more of the antenna elements, each return-radar signal being received before a next antenna element transmits its respective radar signal;

I/Q sampling and demodulating the return-radar signals; and

performing Fourier transforms of the demodulated return-radar signals.

28. The method of claim 27, wherein the next antenna element is the same antenna element of the array.

29. The method of claim 27, wherein the next antenna element is a different antenna element of the array.

30. The method of claim 27, further comprising imaging the Fourier-transformed return-radar signals.

31. The method of claim 30, wherein imaging the Fourier-transformed return-radar signals comprises:

determining respective magnitudes of the return-radar signals in at least one data plane; and

imaging the at least one data plane.

32. The method of claim 27, wherein:

the energization signals are delivered to respective antenna elements one at a time in an ordered manner; and

the return-radar signals are received by the respective antenna elements one at a time in the ordered manner.

33. The method of claim 27, wherein the step of I/Q sampling and demodulating the return-radar signals further comprises:

producing respective I and Q range-resolved signals; and

sorting the I and Q range-resolved signals into range bins to form a set of complex iso-range data planes each holding respective (I/Q) received data values at the respective range.

34. The method of claim 33, wherein the step of performing Fourier transforms further comprises performing multi-dimensional fast-Fourier transforms of respective data values in the complex iso-range data planes.

35. The method of claim 34, wherein the step of performing Fourier transforms further comprises producing, for each of a series of complex input values, a corresponding complex output value having a respective magnitude formed as a square root of a sum of squared real and imaginary values, thereby producing two-dimensional planes of output data, one respective plane for each range.

36. The method of claim 35, further comprising imaging the planes of output data by receiving multiple planes of output data, and producing a multi-dimensional image from said data.