Method and apparatus for interferometric radar measurement

• US 7,336,217 B2
• Filed: 09/20/2005
• Issued: 02/26/2008
• Est. Priority Date: 09/21/2004
• Status: Active Grant

• Current Assignee: Airbus Defence and Space GmbH
• Original Assignee: Eads Astrium GmbH
• Inventors: Voelker, Michael
• Primary Examiner(s): Tarcza; Thomas H.
• Assistant Examiner(s): Chen; Shelley
• Application Number:
  US11/229,639
• Publication Number:
  US 20060164288A1
• Time in Patent Office: 889 Days
• Field of Search: 342/25.C
• US Class Current: 342/25.00C
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/90 using synthetic aperture techniques , e.g. synthetic aperture radar [SAR] techniques
• CPC Class Codes: G01S 13/9023 combined with interferometric techniques
• CPC Class Codes: G01S 13/9058 Bistatic or multistatic SAR
• CPC Class Codes: G01S 7/40 Means for monitoring or calibrating

Abstract

In a method for interferometric radar measurement, at least two side looking RADAR systems on satellite and/or missile-supported platforms illuminate a common surface area by means of microwave signals. A first side looking RADAR system sends a first radar signal on a first transmit frequency, and at least a second side looking RADAR system sends at least a second radar signal on at least a second transmit frequency. At least one of the at least two side looking RADAR systems receives the at least two interfering radar signals reflected on the common surface area, determines difference phases of the received radar signals from the interferograms, determines therefrom a drift of a system clock of the at least two side looking RADAR systems, and compensates the determined drift.

Claims

1. A method for interferometric radar measurement in which at least two side looking RADAR systems, mounted on satellite and/or missile-supported platforms, wherein illuminate a common surface area by means of microwave signals;

wherein;

a first side looking RADAR system sends a first radar signal in a range around a first transmit side looking RADAR frequency;

a second side looking RADAR system sends at least a second radar signal on at least a second transmit frequency; and

at least one of the first and second side looking RADAR systems receives at least two interfering radar signals reflected on the common surface area, and based thereon determines difference phases of the received radar signals by forming at least three interferograms, determines a drift of a system clock of the at least two SAR systems from the difference phases, and compensates the determined drift.

2. The method according to claim 1, wherein each of the first and second side looking RADAR system receives the at least two interfering radar signals reflected on the common surface area, and based thereon determines difference phases of the received radar signals from the at least three interferograms, determines a drift of a system clock of the first and second side looking RADAR systems from the difference phases, and compensates the determined drift.

3. The method according to claim 2, wherein a first interferogram is derived from a radar signal s₁₁ sent and received by the first side looking RADAR system, and from a radar signal s₂₂ sent and received by the second side looking RADAR system.

4. The method according to claim 3, wherein a second interferogram is derived from the radar signal s₁₁, and a radar signal s₁₂ sent by the first side looking RADAR system and received by the second side looking RADAR system.

5. The method according to claim 4, wherein a third interferogram is derived from a radar signal S21 sent by the second side looking RADAR system and received by the first side looking RADAR system and a radar signal sent s₂₂ and received by the second side looking RADAR system.

6. The method according to claim 5, wherein a fourth interferogram is derived from the radar signal s₁₁, and the radar signal s₂₁.

7. The method according to claim 6, wherein a fifth interferogram is derived from the radar signal s₁₂ and the radar signal s₂₂.

8. A system for the interferometric radar measurement having at least two side looking RADAR systems on satellite- and/or missile-supported platforms which illuminate a common surface area by means of microwave signals, including a first side looking RADAR system which can send a first radar signal around a first transmit center frequency, and a second side looking RADAR system which can send at least a second radar signal around at least a second transmit center frequency;

wherein;

at least one of the first and second side looking RADAR systems is constructed for receiving at least two interfering radar signals reflected on the common surface area, for determining, based on said interfering radar signals, difference phases of the received radar signals by forming at least three interferograms.

9. The system according to claim 8, wherein the first and the second side looking RADAR system are constructed for receiving the at least two interfering radar signals reflected on the common surface area, of the at least two side looking RADAR systems, for determining, based on said interfering radar signals, difference phases of the received radar signals from the at least three interferograms, determining a drift of a system clock of the at least two side looking RADAR systems from the difference phases, and compensating the determined drift.

10. The system according to claim 9, wherein the first side looking RADAR system has a steeper incidence angle with respect to the illuminated surface areas than the second side looking RADAR system.

11. The system according to claim 10, wherein the first transmit center frequency is higher than the second transmit center frequency.

12. The system according to claim 11, wherein both the first and the second side looking RADAR system send radar signals on more than one transmit frequency.

13. The system according to claim 12, wherein the first and the second side looking RADAR system send radar signals with more than one polarization.

14. The system according to claim 12, wherein the first and the second radar signals are frequency-modulated continuous signals.

15. The system according to claim 12, wherein the first and the second radar signals are frequency-modulated pulses.

16. The system according to claim 15, wherein the first and the second radar signals are sent within a time-staggered pulse interval.