Efficient Procedure to Design Large Finite Array and Its Feeding Network With Examples of ME-Dipole Array and Microstrip Ridge Gap Waveguide Feed

Abstract

An efficient procedure to design a large planar array and its corporate feeding network is presented. The procedure is verified by $8 \times8$ and $16\times16$ arrays of magnetoelectric dipoles (ME dipole) fed by microstrip ridge gap waveguide (MRGW) through a narrow slot. This procedure is based on using the frequency-dependent effective input impedance at the port of each element, which includes the effect of the mutual coupling between the antenna elements, which is used to design the corporate feeding network. In addition, the far-field characteristics of the array parameters such as directivity, gain, and the radiation patterns are predicted using the pattern multiplication method including the mutual coupling. The results are verified with the full-wave numerical solution. The procedure requires limited resources and speed up the design cycle. In the presented examples, the array elements are directly excited by the MRGW, which provides more flexibility to design complicated feeding networks and allow for distances between the elements less than a wavelength. Therefore, grating lobes are avoided. To accommodate such constraints, special designs of the power dividers are performed to provide the symmetric location of MRGW lines to avoid coupling between the feeding network lines. Furthermore, a transition from waveguide WR-15 to the MRGW is proposed to differential feed of the array antenna. The $16 \times 16$ array of ME dipoles has been fabricated. The measurement results show a 19% matching bandwidth ( $\vert \text{S}11\vert dB) and measured gain above 30 dBi with radiation efficiency better than 71%, all within a common bandwidth of 56–66 GHz.