Slot antennas

This article is dedicated to a type of antenna highly appreciated for the quality of its radiation patterns: the slot antenna. Such an antenna consists of an assembly of rectangular waveguides on which regularly-spaced slots are cut. The network of elementary sources thus formed can be finely controlled in amplitude and phase by "playing" with the geometry or position of the slots on the guides.

In the literature, there are many presentations that "understand" the operation of a slot antenna through the radiation mechanisms of one or more slots. On the other hand, it's much rarer to find lectures on the complete synthesis of an antenna, including the antenna feed. Moreover, while extremely rapid advances in computer power suggest that in the near future we'll be able to analyze large mechanical structures – such as slot antennas – using exact numerical methods, it seems highly unlikely that we'll be able to synthesize such devices using purely numerical methods. It is in this context that reasoned antenna synthesis takes on its full importance and is set out in detail.

After a brief historical review, we'll look at the following themes.

• The first part (§1) covers the basics of slits, slotted waveguides and other antenna components. Slot radiation and its interaction with the waveguide are described.

• The second part describes the synthesis of a slotted antenna, from the objective illumination law to antenna construction. This section also covers the technological aspects, describing how to produce and assemble large metal parts with the required mechanical precision.

• A final, less technical section briefly describes the various applications of slot antennas: lightweight, compact antennas with low losses and good pattern quality. The trade-off for these qualities is a cost that keeps them away from "consumer" applications, but rather destines them for civil or military applications where performance is paramount.

To fully understand this article, you must have read or be familiar with the articles on antennas. , , and passive circuits , .