An investigation into the behaviour of VHF/UHF antennas in the proximity of the human body

• Main Author: Kapartis, S.
• Published: University of Surrey 1984
• Subjects: 621.382
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306657

The subject of this dissertation is the antennas of hand-portable and body-worn transceivers. The human body, within the immediate neighbourhood of the portable antenna, is treated as an integral part of the radiating structure. The resulting body antenna combination is analysed experimentally using a novel technique which was developed as part of the work undertaken. The work is divided into three broad sections; the first is centred on the development of a system capable of measuring the radiation properties of the antenna-body system. The arrangement employed is based on the near-field to far-field spherical scanning technique which for the purpose of the present work is adapted to the particular requirements of VHF/UHF antennas. So far as is known it is the first such facility capable of being used at relatively low frequencies. The second part of the work is concerned with the measurement of antenna impedance. The technique proposed is free from perturbation of the electromagnetic field associated with various methods used in the past. Use is made of a 'single' optical fibre link to transmit the R.F. signals associated with vector impedance measurement to the measuring instrumentation situated at some distance away from the portable antenna. Unlike earlier methods, the one described here can predict the antenna impedance in both modulus and phase and is therefore suitable for the experimental design of matching networks to be used with portables. This design procedure was based in the past on time consuming trial and error techniques. Finally a limited study undertaken on the effect of the human body on the portable antenna is described. The research undertaken is based on a commercial portable radio operating at 167 MHz equipped with a variety of antennas. The study, which makes use of the facilities described earlier, demonstrates that with all known types of portable antennas the effect of the human body is characterized mainly by high energy absorption and severe antenna pattern perturbation.