A Bistatic Imaging Method for GEOSAR in the Strip Mode and UAVSAR in the Steering Beam Mode

Table 1

The geometrical configuration of the GEO-UAV BiSAR. The time-frequency of received signals is plotted from three-point targets in near range (a), center range (b), and far range (c). represents the instantaneous signal bandwidth.

Mode & description	Time-frequency relationship	Geometric construction
Spotlight ()
Azimuth resolution:
Merits: this radar has the higher azimuth resolution than the other three modes
Defects: the surface swath is also smallest [15]
Sliding spotlight ()
Azimuth resolution:
Merits: the receiver operated in a sliding spotlight mode achieves a tradeoff between the azimuth scene size and the azimuth resolution
Defects: as far as going studies in a large number of literatures are concerned, the less imaging method is appropriate [16]
TOPS ()
Azimuth resolution:
Merits: the receiver in this type can switch the antenna to targets pertaining to different subswaths
Defects: this radar has the low azimuth resolution. A less imaging scheme can be applied [17]