Impedance Matching Design of a Low-Profile Wide-Angle Scanning Phased Array

In this paper, an effective method aimed at reducing the mutual impedance among array elements is developed to realize wide-angle impedance matching (WAIM) for planar phased arrays. According to the property of the coupling field, the inherent field distribution at apertures of each element is properly regulated so that the mutual impedance between two arbitrary elements can be substantially reduced. Based on the analysis of the impedance matrix for the equivalent microwave network, the required WAIM can be implemented with such minified mutual impedance. With the proposed method, a low-profile linear phased array with $1 \times 10$ uniform elements is designed and manufactured. For the presented array, the wide-angle scanning performance is attained from the joint effect of the spatial radiation and the surface-wave diffraction. To achieve WAIM, the inherent field of each element is deliberately adjusted according to the distribution of the guided TM surface wave, which acts as the dominant coupling field. Both simulated and experimental results indicate that the proposed phased array can steer its main beam from -81 degrees to +81 degrees in the azimuth plane, with peak realized gain fluctuation less than 3.5 dB. Particularly, besides the broad range of scan, all the active S-parameters are controlled less than -10 dB in the fixed operating band for all scanning angles.