New applications of transponder in focusing distributed synthetic aperture radar data

High-precision phase synchronisation or compensation techniques must be provided for distributed synthetic aperture radar (DiSAR), which operates with separate transmitters and receivers. The use of a novel transponder that was proposed for calibrating high-resolution imaging radars to compensate oscillator frequency instability is investigated here. This transponder modulates the radar pulses in a manner that the retransmitted signal shows two additional Doppler frequencies, which enables their separation from the scene echoes. In this way, DiSAR frequency synchronisation errors can be compensated. Thereafter, the DiSAR raw data is focused by using a derived image formation algorithm. The originality of this text lies in the phase compensation technique via transponder for DiSAR systems, as well as an image formation algorithm with integrated synchronisation compensation.