Low profile cellular radio antenna for ISM applications

A typical handheld cellular phone antenna is realized as a monopole mounted on the top of the transceiver. The omnidirectional radiation pattern of such an antenna ensures reliable communication regardless of its orientation, but part of the power emitted is absorbed by the user´s head. Human body exposure to electromagnetic radiation at frequencies around and above 900 MHz may be hazardous under certain circumstances. The paper deals with antennas that have minimal radiation towards the user´s head while ensuring reliable communication regardless of the antenna orientation. Based on the antenna radiation pattern requirements, we investigate a multilayer microstrip antenna. The obtained experimental results confirm that this antenna can be used effectively as a building block for ISM (2.4 GHz) band applications. The antenna has reduced radiation towards the handset operator´s head and ensures reliable communication regardless of the antenna orientation. The antenna can be produced at low cost, with fairly good matching. The design is straightforward to implement in MMIC and MIC and allows for easy insertion of printed antennas for a multitude of applications.