Abstract
Radar imaging of noncooperative targets is an interesting application of all-weather high-resolution coherent radars. However, these images are usually blurred when using the standard range-Doppler algorithm, if a long coherent processing interval (CPI) is used, and motion compensation techniques are hence necessary to improve imaging quality. If the CPI is reduced enough, target scatterers do not migrate of resolution cells and their corresponding Doppler frequencies are constant. Hence, for a short CPI, motion compensation is not longer necessary, but Doppler resolution gets degraded. In that case, superresolution algorithms may be applied. Here, we compare the superresolution-based focusing techniques with motion compensation-based methods. Our conclusion is that imaging quality after employing the superresolution approaches is not improved and, consequently, the use of motion compensation-based approaches to focus the radar images cannot be circumvented. Simulated and real data from high-resolution radars have been used to make the comparisons.
Highlights
Radar imaging based on a static high-resolution coherent radar is usually referred as Inverse Synthetic Aperture Radar (ISAR) imaging
In ISAR imaging, if the processing interval coherent processing interval (CPI) is not too large, target scatterers do not migrate of resolution cells and their corresponding Doppler frequencies remain constant during the CPI
The ISAR technique is a radar imaging method which may be very interesting in defense and security applications
Summary
Radar imaging based on a static high-resolution coherent radar is usually referred as Inverse Synthetic Aperture Radar (ISAR) imaging. In ISAR imaging, if the processing interval CPI is not too large, target scatterers do not migrate of resolution cells and their corresponding Doppler frequencies remain constant during the CPI For this case, the standard rangeDoppler algorithm (RDA) obtains focused ISAR images. On the other hand, according to (3), if the target is involved in complex motions and the CPI is large, the range from the radar to the scatterer Rs(τ) is a complex function and, the phase of the scatterer φs(τ) is a complex function of the slow-time τ This eventually implies that the scatterer Doppler frequency is not constant during the illumination interval CPI and, if the standard RDA is applied, a severely blurred ISAR image is to be obtained.
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