Modular design of multilayer planar arrays

The problem of multilayered printed antennas is addressed. A conventional corporate feeding network has a crowded layout which can lead to coupling between the network and radiating elements. Furthermore, a conventional feeding network is asymmetric, affecting directly the array performance. It is shown that these problems can be avoided by using a modular design, dividing the network into different stages which are placed on different substrate layers, each shielded by a ground plane. The only possible source of coupling is then between the transitions, which can be located far away from each other. The power transfer between the layers is achieved via coupling apertures. The size of these slots allows much flexibility in design, and fabrication becomes easier. A theoretical model for the transition between the different components is presented, and two practical examples are shown. The equivalent scheme derived for the transition via a rectangular aperture gives very good results for many combinations of planar transmission lines. Practical results for a 16-element array (which includes a three-layer feeding network) demonstrate the effectiveness of this approach.<>