Multi-band Antenna with Minimalization of Radiation towards Head

Intensive development of cellular personal communications system has been ob- served lately. Thus, protection of a man, and especially protection of his head against non-ionizing electromagnetic radiation generated by cellular telephones is becoming one of the most important problems. The results of elaborated microstrip antennas which have minimized radiation towards the user's head are presented in this paper. 1. INTRODUCTION Wireless communication has been the fastest growing sector of telecommunication in recent years. Substantial contributions to this growth has been made in Europe, where many such systems have been developed: GSM (Global System for Mobile Communication), operating in the 900MHz band, DCS-1800 (Digital Personal Communication System), using the 1800MHz band DECT (Digital Eu- ropean (Enhanced) Cordless Telecommunications, using the 1900MHz band and UMTS (Universal Mobile Telecommunications System) working in band circle about 2GHz. Some experts predict that by the end of new century there will be more cordless than conventional telephones in use. In order to achieve an easy access to information, more and more modern cellular phones, which are able to work in two or three bandwidths, are being invented. This is why it is important to determine possible health efiects of using such devices. New trends require antennas to be cheap to produce and to meet tough operational requirements. The following requirements should be met by the antenna: † a radiation pattern ensuring reliable communication regardless of the antenna's orientation; † a wide operational frequency band, so that the spectrum of transmitted information should not be distorted; † a minimum impact on the biological tissue of the user, to avoid health risks; † little sensibility of the antenna parameters to the user's proximity; † small size to facilitate mounting the antenna and using the telephone. It is clear that some of these requirements are mutually exclusive, so a compromise has to be worked out in the designing process. 1m GSM 900 (0.8W) Class 5 0.386W/m 2 0.09W/m 2 0.1W/m 2 GSM 900 (2W) Class 4 1.06W/m 2 0.26W/m 2