Height Measurement with Meter Wave Polarimetric MIMO Radar: Signal Model and MUSIC-like Algorithm

Near space is the key to integrating “sky” and “space” into the future. A synthetic aperture radar (SAR) that works in this area would initiate a technological revolution for remote sensing applications. This study mainly focused on ground moving target imaging (GMTIm) for a near-space hypersonic vehicle-borne SAR (NS-HSV-SAR) with squint angle. The range history, parameter coupling, and Doppler ambiguity of the squint-looking NS-HSV-SAR are more complicated than traditional side-looking airborne or space-borne SARs. Thus, a precise range model is presented on the basis of phase error analyses. Then, all potential distributions of echo’s azimuth spectrum are derived, and a GMTIm method is proposed on the basis of a detailed analysis of the echo characteristics. The proposed method consists of three steps. Firstly, a prior information-based pre-processing function was created to decrease the Doppler ambiguity and range migration effects. Secondly, a blur matched keystone transform was developed to correct the residual range walk migration. Thirdly, a time-saving chirp Fourier transform was investigated for azimuth focusing. Implementation considerations, including the curvilinear trajectory of the NS-HSV-SAR, multiple moving target imaging, and applicability and limitation of the method, are discussed. Finally, simulation results are presented to validate the effectiveness of the proposed method.

Ground Moving Target Imaging and Analysis for Near-Space Hypersonic Vehicle-Borne Synthetic Aperture Radar System with Squint Angle

Clutter suppression and ground moving target imaging approach for hypersonic vehicle borne multichannel radar based on two-step focusing method

An Low-angle target tracking problem is investigated via the refined maximum likelihood (RML) algorithm. The results of the RML algorithm reveal that increasing the operating frequency of radar does not always reduce the mean-squared error (MSE) of angle estimate and thus an appropriate selection of the operating frequency can improve the angle estimation accuracy. Here, a frequency-agile RML algorithm is proposed, which adaptively adjusts the operating frequency during target tracking to minimize the MSEs of angle estimate. Theoretical analysis and simulation are made to verify the effectiveness of the frequency-agile RML algorithm.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-rsn.2016.0301

Low-angle target tracking using frequency-agile refined maximum likelihood algorithm

According to the model of multipath propagation in low-angle tracking, the reflecting surface height has significant influence on the measurement precision of the target height. In this study, a novel method for the joint estimation of the target height and the reflecting surface height is proposed based on multichannel digital array radar. To reduce the computational burden of the proposed method, the projection gradient method instead of two-dimensional search is adopted to minimise the cost function. Moreover, the Cramer–Rao bound of the proposed method is also derived in this study. At last, simulations and practical data processing results show that the proposed method has a good estimation precision.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-rsn.2015.0391

Yu Wang

Papers

Target and reflecting surface height joint estimation in low-angle radar

Clutter suppression and ground moving target imaging approach for hypersonic vehicle borne multichannel radar based on two-step focusing method

Clutter suppression and moving target imaging approach for multichannel hypersonic vehicle borne radar

Joint optimization of PAPR reduction based on modified TR scheme for MIMO-OFDM radar

Space-time coding waveform design for MIMO radar transmit beamforming with minimum MFL