Imaging Approach for FMCW Synthetic Aperture Radar Sensor Using Modified ω-k Method

The radar sensors with the frequency modulation continuous wave system are easily miniaturized for scene imaging on compact platforms, and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\omega $ </tex-math></inline-formula>-k imaging algorithm is widely utilized. However, the conventional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\omega $ </tex-math></inline-formula>-k algorithm for synthetic aperture radar (SAR) imaging may not consider the high-order azimuth spatial-variant nonstationary phase errors. In this article, a novel approach for SAR imaging is developed with a modified <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\omega $ </tex-math></inline-formula>-k method. Under the frequency-modulated continuous radar system, after dechirp operation on the echo signal, a modified time-scaled transformation is proposed to correct the range cell migration (RCM) where the azimuth nonstationary phase information is retained to promote the azimuth focusing. Finally, the well-focused SAR images can be obtained after compensating the intrapulse motion error and the high-order azimuth spatial-variant nonstationary phase errors. Both simulation results of point targets and real-measured FMCW SAR data verify the effectiveness and feasibility proposed algorithm.