Radio-over-fibre systems for body-centric communication measurements

Abstract

Body-centric wireless communication devices are continually required to be smaller, lighter and thinner, and consequently the PCB, components, battery and antenna must become smaller.

The conventional method for measuring an antenna’s performance requires an anechoic chamber coaxial cable measurement system. However, measuring the antenna’s radiation pattern becomes difficult when the relative size of the antenna is smaller than the coaxial cable. Furthermore the difficulty increases when the antenna is in close proximity to the body due to the effects of detuning causing low antenna efficiency. A coaxial cable system produces poor measurement repeatability due to moving cables. This produces variable loss and phase and undesired coupling.

To solve this problem, this thesis describes the design of a novel radio-over-fibre antenna measurement system for on-body channel path measurements. The fibre system is employed to replace coaxial cables with fibre optic cables between the antennas and network analyser at 2.45 Gigahertz for the belt-to-head channel. The simulations are compared to measurements taken in the anechoic chamber. The radio-over-fibre system appears to improve measurement accuracy through an observable improvement in mean forward path gain (S21) of 2.19 dB when compared with the coaxial system. This improvement is most desirable for repeatable on-body measurements.