Passive multi‐static SAR – experimental results

Abstract

This paper experimentally explores the potential of passive multistatic SAR imaging. An experimental campaign was conducted with navigation satellites (e.g. GPS) as transmitters of opportunity. During the experiment, a single receiver recorded satellite signal reflections off a target area from 4 satellites in its field of view. Based on the total recording time and the number of signals processed, a total of 46 bistatic images were obtained. Subsequently, those bistatic images were non-coherently combined into a single multistatic image. The obtained results show that the multistatic image enhances target area information space and can additionally be used to reveal object geometric features such as edges, shape, and dimensions, which are otherwise difficult to observe in passive SAR with its modest spatial resolution. In addition, information obtained from individual images was combined to understand whether or not different object types can be classified based on variations of their bistatic reflections, with promising first results.

Enhanced Passive GNSS-Based Radar Imaging Based on Coherent Integrated Multi-Satellite Signals

“…In the GNSS radar-related research, bistatic imaging scheme [8] is regarded as a conventional scheme, which consists of the stages signal synchronization and radar imaging for individual satellite. Multi-static imaging scheme [9,13,16,18,19], known as the multi-image fusion scheme, is the state-of-the-art scheme, which is functions primarily on the basis of fusing multiple bistatic GNSS radar images. The detailed analysis of these two schemes are given as follows.…”

“…On the basis of GNSS-SAR image formation scheme and GNSS radar RD map forming scheme, the feasibility of GNSS radar imaging was demonstrated under many environmental scenarios [9][10][11][12][13][14][15]. Meanwhile, in recent years, multi-static radar scheme was used for image formation in [9,13,[16][17][18][19] based on multiple bistatic images fusion, which is considered as state-of-the-art imaging scheme in the relevant researches for GNSS radars.…”

“…With such low power density, in many cases, a noisy bistatic GNSS-SAR image or a noisy bistatic GNSS radar RD map occurs. Although multi-image fusion scheme based on different satellites [9,13,16,18,19] can bring some enhancement in image SNR, as multiple full preliminary GNSS radar images are required, it will add a large amount of computational burden for the system. Meanwhile, multi-image fusion is a noncoherent integration scheme, and the respective imaging gain is still lower compared to coherent integration.…”

Passive coherent multistatic SAR using spaceborne illuminators

“…Given a single GNSS constellation, six to eight satellites can simultaneously illuminate any point on Earth, from different viewing angles, with highly stable clocks that may potentially be considered as coherent over a reasonable time. A single receiver can receive and separate these transmitted signals due to their multiple access scheme, which can then be used to form independent bistatic images that can subsequently be combined, either coherently or non‐coherently [17]. In terms of non‐coherent combination, it was shown that two satellites can provide a substantial improvement in resolution, but to do so requires special satellite trajectories and complex signal processing to compensate for artefacts arising from non‐coherent techniques [18, 19].…”