Planar 9-element quasi-Yagi antenna array for X-band application

In this paper, a new planar antenna array based on 9 identical quasi-Yagi elements is presented. In contrast to conventional designs, the feeding network is composed of 3-way power dividers, which are carefully designed in order to provide synchronised output signals over a wide frequency range. The use of spline-shaped microstrip lines suppresses coupling effects by parallel lines. Thus, signal distortions within the feeding network are minimised. Compared to conventional designs with 8 elements, the additional antenna element will enhance the gain of the array, which is between 10.5 and 13 dB in the X-band. The input return loss of the antenna array is below -15 dB over most parts of the relevant spectrum, with a total bandwidth of 45%. The planar antenna array is well-suited as a radiating element in linear phased arrays for multifunction radars including SAR and MTI.