Multiple-input Multiple-output Synthetic Aperture Radar Research Articles

Virtual Antenna Array Analysis for MIMO Synthetic Aperture Radars

Multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) that employs multiple antennas to transmit orthogonal waveforms and multiple antennas to receive radar echoes is a recently proposed remote sensing concept. It has been shown that MIMO SAR can be used to improve remote sensing system performance. Most of the MIMO SAR research so far focused on signal/data models and corresponding signal processing algorithm. Little work related to MIMO SAR antenna analysis can be found. One of the main advantages of MIMO SAR is that the degrees of freedom can be greatly increased by the concept of virtual antenna array. In this paper, we analyze the virtual antenna array for MIMO SAR high-resolution wide-swath remote sensing applications. The one-dimensional uniform and nonuniform linear antenna arrays are investigated and their application potentials in high-resolution wide-swath remote sensing are introduced. The impacts of nonuniform spatial sampling in the virtual antenna array are analyzed, along with a multichannel filtering-based reconstruction algorithm. Conceptual system and discussions are provided. It is shown that high operation flexibility and reconfigurability can be obtained by utilizing the virtual antenna arrays provided by the MIMO SAR systems, thus enabling a satisfactory remote sensing performance.

Shifting MIMO SAR System for High-Resolution Wide-Swath Imaging

A multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) system is presented for high-resolution wide-swath imaging. For a system with N transmit and N receive antennas, the proposed method using slope-varying chirp signals, azimuth beamwidth extension, and transmit antenna shift can give an increased azimuth resolution or a decreased pulse repetition frequency (PRF), which results in wider swath width, by a factor of N compared to a SAR system based on a displaced phase center antenna. To verify the proposed shifting MIMO SAR system, we carried out the point target simulations and the timing analysis which showed enhanced resolution and widened swath width performances.

APPLICATION OF COMPLETE COMPLEMENTARY SEQUENCE IN ORTHOGONAL MIMO SAR SYSTEM

The Complete Complementary Sequence (CC-S) consists of several complementary orthogonal sequences and has optimal sidelobe level performance, which is satisfled with the requirement of the orthogonal Multiple Input Multiple Output (MIMO) radar signals. Aimed at the di-culty of high sidelobe level in Synthetic Aperture Radar (SAR) imaging processing in range dimension, an approach of depressing sidelobe level based on CC-S in MIMO SAR system was proposed. The transmitter model for orthogonal MIMO SAR system using CC-S and the corresponding matched fllter (MF) were established in this paper. In addition, the MIMO SAR imaging results were simulated. The simulation results demonstrate that the performance of CC-S employed in orthogonal MIMO radar system is much better than that with traditional Linear Frequency Modulation (LFM) signal, by which the feasibility and validity of CC-S applied in orthogonal MIMO SAR system are justifled.

Sparse, Active Aperture Imaging

We describe an approach to radar imaging of an isolated, rotating target using coherent, sparse, or highly thinned arrays of transmit/receive elements. The array elements are assumed to be randomly positioned and accurately surveyed after placement. Further, the isolated target is assumed to occupy a limited angular sector such that there is no source of backscatter beyond the sector occupied by the target. Estimates of the resolution and image quality are provided when the array elements are widely separated and operate with coherent, multiple-input multiple-output (MIMO) signaling and inverse synthetic aperture radar (ISAR) processing at each MIMO element pair. The sparse array operation can provide superior resolution when compared to the ISAR processing and accurate estimation of scattering properties with a modest number of sparse array elements. The performance of a model-based estimator to physical optics like scattering with MIMO signaling is described. Several important issues relating to feasibility remain to be investigated. These include establishing coherence and timing among the widely separated array elements, adaptive beamforming and processing requirements and coherence of the scattering phenomena with the widely separated MIMO elements.