Analysis of a Bistatic Ground-Based Synthetic Aperture Radar System and Indoor Experiments

Abstract

Recent advancement of satellite synthetic aperture radar (SAR) techniques require more sophisticated system configurations such as the use of bistatic antennas or multi-frequencies. A ground-based experiment is a cost-effective and efficient way to evaluate those new configurations especially in the early stage of the system development. In this paper, a ground-based synthetic aperture radar (GB-SAR) system was constructed and operated in a bistatic mode at Ku-band where a receiving antenna (Rx) follows a transmitting antenna (Tx) separated by a baseline B. A new bistatic GB-SAR focusing algorithm was developed by modifying a conventional range-Doppler algorithm (RDA), and its performance has been evaluated by comparing the results with those from a back-projection algorithm (BPA). The results showed good performance of RDA at far range approaching nominal resolutions of 9.4 cm in range and 4.5 cm in azimuth, but limited quality at near range due to the approximation used in RDA. Signals from three trihedral corner reflectors (CR) reduced with increasing B, showing a typical bidirectional scattering behavior of CR. This GB-SAR system will be a testbed for new SAR imaging configurations with variations in antenna positions and target properties.

Indoor Experiments of Bistatic/Multistatic GB-SAR with One-Stationary and One-Moving Antennae

“…The location of the experiment and the GB-SAR system used for the one-stationary and one-moving antennae configuration in this paper was almost identical to [19]. A lecture room measured 8 m × 10 m was equipped with the array of desks and chairs, lecturer's desks and a blackboard.…”

“…The range time resolution can be defined to be δt = 1/B R assuming a point target with a scattering coefficient of a delta function, g(t) = δ(t − t 0 ). The (slant) range resolution is then δr = c/(2B R ) for a monostatic radar [19].…”

“…The iso-range planes are ellipsoids with two focal points located at each antenna position. As in [19], a bistatic range, r B , can be defined as a coordinate with the origin at the center of an iso-range ellipse and the direction of the semi-minor axis, so that r B = r 2 − (B/2) 2 where the monostatic range r is the distance from the antenna to a target in the direction of r B . The ratio of the two resolutions can be defined by [19] δr…”

“…Pieraccini et al [18] obtained displacement vectors of a target by redirecting the transmitted signal using a ground-based transponder. Recently, Lee and Moon [19] have tested a bistatic GB-SAR configuration where two antennae separated by a baseline are moving on a linear rail simultaneously.…”

“…In this paper, a bistatic GB-SAR system was operated in a lecture room with one antenna moving along a linear rail while the other was stationary on the ground. The RF and rail systems used in this paper were similar to [19] except for the antenna configuration. Multiple bistatic images were obtained with different positions and viewing angles of the stationary antenna in order to have SAR images with omni-directional scattering properties of a target.…”