Grating-Lobe Mitigation Using Parasitic Scatterers and Principal Component Analysis

This communication presents a method for suppressing grating lobes that occur in sparse antenna arrays. The method is based on parasitic antenna elements that are terminated to reactive loads. The loads are computed using a computationally efficient algorithm that is based on principal component analysis (PCA) and strives to maximize realized gain toward grating-lobe-free (GL-free) scan directions. The developed method is demonstrated at 5 GHz by both electromagnetic simulations and prototype measurements using a
$3\times3$
element antenna array with one-wavelength interelement distances. The example shows that the grating-lobe level is suppressed by 8.4 dB, and the main beam gain is increased by 3.9 dB compared to an array without parasitic scatterers.