Radar system

• US 8,362,944 B2
• Filed: 07/17/2009
• Issued: 01/29/2013
• Est. Priority Date: 04/21/2009
• Status: Active Grant

• Current Assignee: Astrium Limited (Airbus SE)
• Original Assignee: Astrium Limited (Airbus SE)
• Inventors: Lancashire, David Charles
• Primary Examiner(s): GREGORY, BERNARR E
• Application Number:
  US12/504,933
• Publication Number:
  US 20100265123A1
• Time in Patent Office: 1,292 Days
• Field of Search: 342 25 R- 25 F, 342 73- 82, 342 89-103, 342/147, 342/158, 342/175, 342/195, 342/157, 342368-377, 342/118, 342128-145
• US Class Current: 342/81
• CPC Class Codes: G01S 13/904 SAR modes
• CPC Class Codes: G01S 2013/0254 Active array antenna
• CPC Class Codes: H01Q 21/0006 Particular feeding systems
• CPC Class Codes: H01Q 21/22 Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array
• CPC Class Codes: H01Q 3/36 with variable phase-shifters
• CPC Class Codes: H01Q 3/385 Scan control logics

Abstract

A radar system is disclosed for forming a scanning receive beam from signals received by a phased array having a plurality of sub arrays. An exemplary radar system includes a plurality of phase units each configured to receive a signal from one or more sub arrays. Each phase unit includes a waveform generator configured to generate an analog waveform having a frequency corresponding to a time-varying phase shift. Each waveform generator is arranged to digitally generate the analog waveform, and output a comparison of the received signal with the waveform, incorporating the time-varying phase shift. The system further includes a combining unit configured to combine the outputs from the plurality of phase units to form a scanning receive beam.

Claims

1. A radar system for receiving reflected signals from a scanned area in a phased array having a plurality of sub arrays,

the system comprising:

a plurality of phase units each configured to receive a signal from one or more sub arrays;

wherein each phase unit comprises a waveform generator configured to generate an analog waveform having frequency adjacent phase units generating frequencies which differ by an offset frequency; and

wherein each waveform generator is arranged to digitally generate the analog waveform, and

each phase unit is configured to output a comparison of the received signal with the analog waveform, the output incorporating the offset frequency, and

the system further comprising a combining unit configured to combine the outputs from the plurality of phase units to receive reflected signals from the scanned area.

2. The radar system as claimed in claim 1 wherein the waveform generator generates the digitally controlled analog waveform by Direct Digital Synthesis.

3. The radar system as claimed in claim 2 wherein the waveform generator using Direct Digital Synthesis comprises:

a logic function to generate a sequence of digital representations of a required phase; and

a digital-to-analog converter (DAC) to convert the required phase to the analog waveform.

4. The radar system as claimed in claim 1, wherein each of the plurality of phase units comprises:

a mixer for comparing the received signal with the analog waveform,

each mixer being configured to mix said signal from one or more sub arrays with the analog waveform.

5. The radar system as claimed in claim 1, wherein the waveform generators are synchronized, and each waveform has a unique frequency.

6. The radar system as claimed in claim 1, wherein the waveform generator in each phase unit digitally stores a starting phase of the waveform, such that the scanned area has a defined direction on starting scanning.

7. The radar system as claimed in claim 1, wherein the analog waveform has a frequency formed from a base frequency common to the waveform generators and the applied offset frequency.

8. The radar system as claimed in claim 1, configured to receive echoes of radar transmission pulses transmitted over an area,

wherein the reflected signals are focused on a part of the area,

and the radar system is configured to scan the reflected signals across the area at a rate substantially matching an echo of said a radar transmission pulses from across the area.

9. The radar system as claimed in claim 8, configured to scan the reflected signals across the area in a time less than a time between consecutive transmission pulses.

10. The radar system as claimed in claim 1, wherein the frequency of each analog waveform is varied during a scan such that the reflected signals are scanned at an angular rate which varies with time.

11. The radar system as claimed in claim 1, wherein the frequency of the analog waveform is varied during a scan such that the scanned area width varies with time.

12. The radar system as claimed in claim 1, wherein the frequency of the analog waveform is constant during a scan such that the scanned area is scanned at a constant angular rate and with a constant width.

13. The radar system as claimed in claim 1, wherein each of the plurality of phase units is configured to receive a signal from a single sub array, or from a group of sub arrays.

14. The radar system as claimed in claim 1, configured to be mounted in at least one moving platform and scan the reflected signals in a sideways direction perpendicular to a direction of travel of the platform.

15. A radar system module for insertion in an existing radar system, the module comprising:

a plurality of phase units each configured to receive a signal from one or more sub arrays;

wherein each phase unit comprises a waveform generator configured to generate an analog waveform having a frequency wherein adjacent phase units generate frequencies which differ by an offset frequency; and

wherein each waveform generator is arranged to digitally generate the analog waveform, and

each phase unit is configured to output a comparison of the received signal with the analog waveform, the output incorporating the offset frequency, and

the system further comprising a combining unit configured to combine the outputs from the plurality of phase units to receive reflected signals from a scanned area at an output frequency; and

a frequency converter arranged to convert the output frequency from the combining unit to substantially a same frequency as the signals received by the sub arrays.

16. The radar system as claimed in claim 15, wherein the waveform generators are synchronized, and each waveform has a unique frequency.

17. The radar system as claimed in claim 16, wherein the waveform generator in each phase unit digitally stores a starting phase of the waveform, such that the scanned area has a defined direction on starting scanning.

18. The radar system as claimed in claim 17, wherein the analog waveform has a frequency formed from a base frequency common to the waveform generators and the applied offset frequency.

19. The radar system as claimed in claim 18, configured to receive echoes of radar transmission pulses transmitted over an area,

wherein the reflected signals are focused on a part of the area,

and the radar system is configured to scan the reflected signals across the area at a rate substantially matching an echo of said a radar transmission pulses from across the area.

20. The radar system as claimed in claim 19, wherein the frequency of each analog waveform is varied during a scan such that the is reflected signals are scanned at an angular rate which varies with time.