Abstract
The stochastic characteristic of the radiation field of a mono-static microwave staring correlated imaging (MSCI) radar degenerates with the increase of the imaging distance, which results in degradation of the image quality. To address this issue, a novel MSCI method based on bi-static radar is proposed from two perspectives: site-deploying and waveform design. On the one hand, a new bi-static MSCI site-deploying scheme is proposed which adopts two transmitting stations with their azimuth angles relative to the center of the imaging region differing by 90 degrees. On the other hand, by using two transmitting arrays synchronously transmitting inner-and-inter pulse frequency hopping (IAIP-FH) signals, the radiation field of each station includes a few “frequency stripes” perpendicular to the radiation direction, and as a consequence, the “frequency stripes” of each radiation field are perpendicular to each other. As a result, the radiation field of the bi-static MSCI is the superposition of the two striped radiation fields, thus a latticed radiation field is constructed. Therefore, the targets in different latticed grids scatter independent fields, then, the images can be reconstructed using correlation process (CP) algorithms. The grid size of the latticed radiation field is determined by the inner-pulse frequency hopping (FH) interval of the IAIP-FH signals and the imaging geometry. Moreover, it is shown that the 3 dB beam width of the space correlation function of the radiation field does not change with the imaging distance, thus the stochastic characteristic of the radiation field is partly preserved when the imaging distance increases. Simulation results validate the analysis and show that the proposed method can obtain higher resolution images than the common mono-static MSCI method.
Highlights
The radar imaging technique has the ability of working all-day and in all weathers [1,2], it has attracted increasing attentions and extensive researches, among which earth observation is an important application field [3].The conventional high-resolution radars for earth observation commonly employ theRange-Doppler (RD) principle [4] or tomography theory [5] to acquire two-dimensional high-resolution images, e.g., synthetic aperture radar (SAR) [6,7,8], etc
A new site-deploying scheme for bi-static microwave staring correlated imaging (MSCI) is proposed, and its key point is that the two transmitting arrays observe the imaging area from two azimuth angles which differ by 90 degrees
The detailed imaging procedure of the proposed method is as follows: (1) perform site-deploying to satisfy the requirements of the proposed imaging geometry; (2) the two random radiation source (RRS) synchronously transmit the inner-and-inter pulse frequency hopping (IAIP-frequency hopping (FH)) signals to construct a latticed field at the imaging plane; (3) sample the received signal and compute the modified radiation field matrix based on the waveform parameters; (4) correlation process (CP) of the sampled signal and the matrix to obtain the image
Summary
The radar imaging technique has the ability of working all-day and in all weathers [1,2], it has attracted increasing attentions and extensive researches, among which earth observation is an important application field [3]. Reference [22] introduced metamaterial apertures [23,24,25,26] into the MSCI, and proposed employing the secondary scattering of a meta-surface to achieve a better radiation field. Multi-static radars observe the targets from more and larger aspect angles, have the potential to form TSSRF with a better stochastic characteristic. The resolution of MSCI is not determined by the aperture size but by the stochastic characteristic of the TSSRF, and multi-static radar systems greatly increase the system cost and complexity.
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