A Precise Wavenumber Domain Algorithm for Near Range Microwave Imaging by Cross MIMO Array

An electronically large planar antenna with wideband illumination retrieves 3-D microwave image with high resolution. Cross multi-input-multi-output (MIMO) topology is commonly used to produce the effective planar array at a reasonable cost and complexity. However, the imaging algorithm for effective monostatic array will cause distortion and dispersion in near range imaging applications. In this paper, an efficient and precise algorithm for near range imaging by cross MIMO array is proposed. The integrals over the transmitting and receiving arrays are carried out in the wavenumber domain to improve efficiency. No approximation is made to further decouple the space and wavenumber variables so the reconstructed image precisely retains both intensity and phase information. The algorithm achieves the same imaging quality as the back-propagation algorithm at the computation complexity of O(N4lgN). It can also be implemented to boundary arrays by coherent subarray superposition. Experiments using both simulated and measured data verify its performance. The point spread function and resolution of cross MIMO topology are discussed based on the images reconstructed by this algorithm using measured data.