Annular Slots with Cardioid-Type Patterns.
Koichi Ayabe, Benedikt A. Munk · Defense Technical Information Center (DTIC) · 1980
This report considers the radiation pattern from one or more concentric circular loops. The current on each loop is comprised of components of the form sin n(phi). It is shown how directive patterns with one and more nulls can be obtained in particularly a true cardioid pattern. Particular attention is given to the tolerances in order to maintain a reasonable sharp null. (Author)