Method and system for real-time phase synchronization of a SAR system

Abstract

A method for real-time phase synchronization of a SAR system (100) is proposed, in which radar signals are emitted by a transmitter (10) via a SAR sensor system (14) and radar echoes of reflected radar signals are received by at least one receiver (20), which includes a SAR sensor system (24), wherein the transmitter (10) and the at least one receiver (20) are located on different platforms. The transmitter (10) and the at least one receiver (20) perform, in particular iteratively, the following steps: At a first time (ta), the transmitter (10) generates and transmits a reference pulse (RP) to the receiver (20) via an optical channel (30), wherein the reference pulse (RP) is derived in phase from a reference frequency (fref,1) of the transmitter (10).The receiver (20) receives the reference pulse (RP) at a second time point (tb) and, using a phase detector, determines the phase relationship between the reference pulse (RP) and a local reference frequency (fref,2) of the receiver (20). The receiver (20) determines time-of-flight correction data (KT) from a time-of-flight measurement of a measurement pulse (MP), which is sent by the receiver (20) to the transmitter (10) via the optical channel (30) at a third time point (tc), and whose return pulse (BP) is received by the receiver (20) at a fifth time point (te). The receiver (20) corrects the phase relationship between the time-of-flight correction data (KB), thereby obtaining a corrected phase relationship.The local reference frequency (fref,2) of the receiver (20) is controlled by the receiver (20) with a control parameter (u) derived from the corrected phase angle, so that the phases of the reference frequency (fref,1) of the transmitter (10) and the local reference frequency (fref,2) of the receiver (20) are constant relative to each other.