Extremum points of range-surface and doppler-surface for airborne bistatic SAR

In the SAR system, some closed iso-range or iso-Doppler contours in the area illuminated by the transmitter mean the ambiguity of some scattering points. However, whether the iso-range or iso-Doppler contours will be closed is closely related with the extremum points of range-surface or Doppler- surface. Therefore in the paper the extremum points of range-surface and Doppler-surface for airborne bistatic SAR with arbitrary geometrical configuration have been studied according to several mathematical models related to range and Doppler of bistatic SAR. The formula for calculating the position of extremum point of range-surface has been given and several important conclusions about the stagnation or extremum points of Doppler-surface have been drawn. The simulation results are provided and the theoretical analyses are validated.