RADAR SYSTEM

• US 20100265123A1
• Filed: 07/17/2009
• Published: 10/21/2010
• 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
• Granted Patent: US 8,362,944 B2
• Time in Patent Office: Days
• US Class Current: 342/175
• 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 forming a scanning receive beam from signals received by 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 a frequency corresponding to a time-varying phase shift; 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 time-varying phase shift, and

the system further comprising a combining unit configured to combine the outputs from the plurality of phase units to form a scanning receive beam.

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

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

6. A 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 scanning receive beam has a defined direction on starting scanning.

7. A 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 an applied offset frequency corresponding to the time-varying phase shift.

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

wherein the scanning receive beam generated is focused on a part of the area,

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

9. A radar system as claimed in claim 8, configured to scan the scanning receive beam across the area in a time less than a time between consecutive transmission pulses.

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

11. A radar system as claimed in claim 1, wherein the frequency of the analog waveform is varied during a scan such that the scanning receive beam width varies with time.

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

13. A 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. A radar system as claimed in claim 1, configured to be mounted in at least one moving platform and scan the scanning receive beam in a sideways direction perpendicular to a direction of travel of the platform.

16. A radar system as claimed in claim 4, wherein the waveform generators are synchronized, and each waveform has a unique frequency.

17. A 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 scanning receive beam has a defined direction on starting scanning.

18. A 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 an applied offset frequency corresponding to the time-varying phase shift.

19. A radar system as claimed in claim 18, configured to receive echoes of radar transmission pulses transmitted over an area, wherein the scanning receive beam generated is focused on a part of the area, and the radar system is configured to scan the scanning receive beam across the area at a rate substantially matching an echo of said a radar transmission pulses from across the area.

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

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 corresponding to a time-varying phase shift; 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 time-varying phase shift, and

the system further comprising a combining unit configured to combine the outputs from the plurality of phase units to form a scanning receive beam with an output frequency; and

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