Thinned Array with Steerable Nulls to cancel Grating Lobe for Automotive Radar Applications

Abstract

A novel thinned antenna element distribution for cancelling grating lobes (GLs) as well as for reducing phase shifters (PSs) is presented for a two-dimensional phased-array automotive radar application. First, an efficient grouping technique of vertical adjacent elements is employed with array thinning for a PS reduction of 66.7%. In the proposed distribution, several single-element radiators (non-grouped antenna elements) are placed in vertical direction with spacing <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$d=(0.5+m)\times \lambda (m$</tex> is integer) in a grid of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$16\times 12(192)$</tex> elements with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda/2$</tex> pitch. This disrupts the periodicity of phase-centers after element-grouping and takes a role as steerable null filters with capabilities of tracking and nullifying the GL at any scan angle. The proposed distribution enables beam steering up to ±60° in the azimuth plane, as well as ±25° in the elevation plane with cancelled GL and side-lobes. Furthermore, the proposed distribution has been efficiently calibrated with all elements activated by introducing code division multiple access (CDMA) technique. To the best of our knowledge, this work represents the first fully calibrated state-of-the-art thinned distribution phased-array including novel steerable null filters to track and nullify GLs.