Piotr Laskowski

MIMO-SAR and the orthogonality confusion

This paper reviews radar architectures that employ multiple transmit and multiple receive channels to improve the performance of synthetic aperture radar (SAR) systems. These advanced architectures have been dubbed multiple-input multiple-output SAR (MIMO-SAR) in analogy to MIMO communication systems. Considerable confusion arose, however, with regard to the selection of suitable waveforms for the simultaneous transmission via multiple antennas. In this paper, it is shown that the mere use of orthogonal waveforms is insufficient for the desired performance improvement in view of most SAR applications. As a solution to this fundamental MIMO-SAR problem we had previously suggested to exploit the special data acquisition geometry of a side-looking imaging radar equipped with multiple receiver channels in addition to appropriately designed waveforms transmitted by multiple antennas. Here, we extend this approach to a more general set of radar waveforms with special correlation properties that satisfy a short-term shift-orthogonality condition. We show that the echoes from simultaneously transmitted pulses can be separated if the short-term shift orthogonality is combined with digital beamforming on receive in elevation. This enables the implementation of a fully functional MIMO-SAR without correlation noise leakage for extended scattering scenarios.

Digital Beam-Forming reconfigurable Radar System demonstrator

Synthetic Aperture Radar (SAR) based on the Digital Beam-Forming (DBF) concept belongs to the family of Multi-Modal Radar Systems (MMRS) offering higher operational flexibility and improved performance compared to conventional radar systems using analog beam steering. DBF SAR, in particular, overcomes the fundamental limitation of classical SAR systems and can deliver high resolution and simultaneously wide swath images. The purpose of this paper is to present a laboratory prototype of such a MMRS architecture - a reconfigurable radar demonstrator based on the DBF architecture. A hardware configuration of the radar as well as advanced concepts to be experimentally verified using it are considered and discussed.

Exploring the trade-space of MIMO SAR

The term MIMO SAR is used for Synthetic Aperture Radar (SAR) systems utilizingmultiple-receive andmultiple-transmit channels (Multiple-Input Multiple Output: MIMO). The trade-space for such SAR systems includes the instrument and antenna parameters taking into consideration the techniques, i.e. the operation modes of the radar. The purpose of exploring this trade-space is to improve and optimize the performance of the system, described through the performance parameters. The aim of this paper is to show examples of how MIMO SAR offers new and unexpected ways of trading the system and performance parameters versus each other. Adequately exploring the trade-space yields a high flexibility and allows to simultaneously improve multiple performance parameters; a feature not available in conventional single channel SAR systems. The content of this paper is considered novel in the sense that it deals with highly advance SAR techniques.

Error analysis and calibration techniques for multichannel SAR instruments

Future spaceborne Synthetic Aperture Radar (SAR) systems will be based on multiple transmit/receive channels and use Digital Beam Forming (DBF) technique and on board processing to provide high coverage and high resolution simultaneously. Due to the necessary on board processing and required alignment between the signals from different channels by the multi-channel operation, a big challenge in the system calibration arises. To manage that issue, new techniques have to be identified and verified. This paper presents the analysis of the effect of system and calibration errors on the SAR image quality for an example multi-channel spaceborne SAR system, which should give a starting point in the calibration accuracy considerations. Further, some ideas for the error correction in the data processing are given and computation results shown.

Development of a MIMO Radar System demonstrator - Calibration and demonstration of first results

Multi-Modal Radar Systems (MMRS) using Digital Beam-Forming (DBF) concept offer higher operational flexibility and improved performance compared to the conventional radar systems using analog beam steering. In particular, Synthetic Aperture Radar (SAR) based on DBF concept overcomes the fundamental limitation of classical SAR systems delivering high resolution and simultaneously wide swath images. This paper presents a laboratory prototype of the next generation MMRS system - a reconfigurable Multiple Input Multiple Output (MIMO) radar demonstrator based on the DBF architecture. The hardware configuration of the demonstrator is described in detail, and the system calibration and signal processing procedures are considered. The first measurement results confirming its functional capabilities are presented and discussed.