Abstract
Imaging and recognition of targets with complex maneuvers bring a new challenge to conventional radar applications. In this paper, the three-dimensional (3D) high-resolution image is attained in real-time by a Multiple-Input-Multiple-Output (MIMO) radar system with single Orthogonal-Frequency-Division-Multiplexing (OFDM) pulse. First, to build the orthogonal transmit waveform set for MIMO transmission, we utilize complex orthogonal designs (CODs) for OFDM subcarrier modulation. Based on the OFDM modulation, a preprocessing method is developed for transmit waveform separation without conventional matched filtering. The result array manifold is the Kronecker product of the steering vectors of subcarrier/transmit antenna/receive antenna uniform linear arrays (ULAs). Then, the high-resolution image of target is attained by the Multidimensional Unitary Estimation of Signal Parameters via Rotational Invariant Techniques (MD-UESPRIT) algorithm. The proposed imaging procedures include the multidimensional spatial smoothing, the unitary transform via backward-forward averaging, and the joint eigenvalue decomposition (JEVD) algorithm for automatically paired coordinates estimation. Simulation tests compare the reconstruction results with the conventional methods and analyze the estimation precision relative to signal-to-noise ratio (SNR), system parameters, and errors.
Highlights
In the past few years, the OFDM waveform has been demonstrated as a potential radar waveform [1,2,3,4,5,6,7,8]
Each subcarrier could be modulated by a phase code sequence; an OFDM pulse [5] has high spectral efficiency as linear frequency modulation (LFM) pulse, along with a bit-to-bit diversity as the phase-coded pulse
We use the simulated data for the 127-point scatterer model of a Boeing 777 airplane to verify the performance of the proposed 3D imaging method. e target scatterer model is depicted in Figure 2, including the projection in each plane and the 3D image
Summary
In the past few years, the OFDM waveform has been demonstrated as a potential radar waveform [1,2,3,4,5,6,7,8]. E OFDM-MIMO radar configuration is applied in this paper to reduce antennas used for 3D imaging and remove the range alignment steps. To break the Rayleigh criterion of minimum resolvable separation, we present a 3D imaging method based on the Estimation of Signal Parameters via Rotational Invariant Techniques (ESPRIT) algorithm. E ESPRIT algorithm is a commonly used high-resolution parameter estimation method [39,40,41] It exploits the rotational invariance among the signal subspace and has no searching process as in the MUltiple SIgnal Classification (MUSIC) techniques. Three problems have to be taken into account for the ESPRIT algorithm applied in OFDM-MIMO radar imaging. We first establish an OFDM-MIMO radar imaging model based on OFDM’s multicarrier structure; the echo is preprocessed to construct the data vector that suits the ESPRIT form.
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