Analytical study of a planar loop antenna with U-shape notch

A small planar loop antenna is appropriate antenna for small radio devices, like pagers, because they offer a high gain near the human body and low antenna loss. Some card style pagers use a planar loop antenna, which is constructed on the surface of the pager housing, and internal electronic circuits, which lie within the loop area of the antenna. This construction is employed to realize the maximum antenna area. However, some windows on the housing are needed to set the display, switches and the cap of a battery holder etc., so the planar antenna element of a card style pager must be pierced to make these windows. The paper introduces an analytical study on the effects of a U-shape notch on a small planar loop antenna. The moment method is used for this analysis. The dependency of the input impedance, antenna efficiency and radiation pattern on the depth of the U-shape notch is investigated.