Synthetic aperture radar hybrid-polarity method and architecture for obtaining the stokes parameters of a backscattered field

• US 7,746,267 B2
• Filed: 05/07/2008
• Issued: 06/29/2010
• Est. Priority Date: 05/08/2007
• Status: Active Grant

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Raney, Russell K.
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Barker; Matthew M
• Application Number:
  US12/116,357
• Publication Number:
  US 20090224964A1
• Time in Patent Office: 783 Days
• Field of Search: 342/25.F
• US Class Current: 342/25.00F
• CPC Class Codes: G01S 13/90 using synthetic aperture techniques , e.g. synthetic aperture radar [SAR] techniques
• CPC Class Codes: G01S 13/904 SAR modes
• CPC Class Codes: G01S 13/9056 Scan SAR mode
• CPC Class Codes: G01S 13/9076 Polarimetric features in SAR
• CPC Class Codes: G01S 7/026 involving the transmission of elliptically or circularly polarised waves

Abstract

A synthetic aperture radar hybrid-polarity method and architecture comprising transmitting circular polarization (by driving the orthogonal linear feeds simultaneously by two identical waveforms, 90° out of phase), and receiving horizontal (H) and vertical (V) linear polarizations, coherently. Once calibrated, the H and V single-look complex amplitude data are sufficient to form all four Stokes parameters, which fully characterize the observed backscattered field.

Claims

1. A method for obtaining the Stokes parameters representing a backscattered field from a partial polarimetric synthetic aperture radar (SAR) comprising the steps of:

transmitting a circularly polarized field by the SAR;

receiving a coherently dual linear polarized backscattered field; and

using data embedded in the received backscattered field to obtain the Stokes parameters.

2. The method as recited in claim 1, wherein the transmitting step comprises the step of driving two orthogonal linear feeds simultaneously by two identical waveforms, the waveforms being 90 degrees out of phase.

3. The method as recited in claim 1, further comprising the step of applying a decomposition methodology to analyze the data using the Stokes parameters.

4. The method as recited in claim 3, the applying a decomposition methodology step comprising the step of calculating a 2×

2 coherency matrix.

5. The method as recited in claim 3, the calculating step further comprising calculating a degree of polarization and a relative phase.

6. A partial polarimetric synthetic aperture radar (SAR) for obtaining the Stokes parameters representing a backscattered field comprising:

a dual linearly-polarized antenna comprising a horizontal (H) feed and a vertical (V) feed;

a transmitter operatively connected to the antenna;

a 90 degree hybrid operatively connected to the transmitter and the antenna for simultaneously driving the H and V feeds 90 degrees out of phase thereby causing the antenna to radiate a circularly polarized field;

a receiver operatively connected to the antenna for receiving a coherent H and V linearly polarized backscattered field; and

a processor operatively connected to the receiver for obtaining the Stokes parameters from data embedded in the backscattered field.

7. The SAR as recited in claim 6, wherein the SAR is operated in ScanSAR mode thereby achieving simultaneously wide swath coverage and polarimetric measurements.

8. The SAR as recited in claim 6, wherein the antenna comprises an active array of transmit/receive modules, each module comprising H and V feeds which on transmit are driven simultaneously 90 degrees out of phase by nominally identical signals.

9. The SAR as recited in claim 8, wherein the SAR is operated in ScanSAR mode thereby achieving simultaneously wide swath coverage and polarimetric measurements.

10. The SAR as recited in claim 6, further comprising a decomposition methodology for analyzing the data using the Stokes parameters.

11. The SAR as recited in claim 10, wherein the decomposition methodology comprises calculating a 2×

2 coherency matrix.

12. The SAR as recited in claim 10, wherein the decomposition methodology comprises calculating one of a degree of polarization and a relative phase.