Cross-range calibration of interferometric ISAR under a condition of phase ambiguity

The cross-range measurement of a target from Interferometric ISAR (InISAR) can usually be obtained from the interferometric phase of echo. However, the phase which has been received is often ambiguous and the reference point on the target used for phase unwrapping with determined location does not really exist, as a result of which, the accurate value of interferometric phase can not be got easily. By deriving the relationship between interferometric phase and cross-range measurement of InISAR image, a method of cross-range calibration under a condition of ambiguous phase is proposed in this paper, using phase difference between adjacent scatters of the same range cell. In addition, equivalent phase compensation for scatters in different range cells ensures that the interferometric phase information of each strong scatter can be fully used during calibration, which can greatly reduce the influence of noise. The simulation result shows the effectiveness of the method.