Numerical analysis of detuning in printed inverted F antennas for Bluetooth applications

In this paper the numerical modelling of an inverted-F antenna (IFA) integrated into a small PCB is described. The transmission line modelling method was used, and a good agreement was obtained between models and measurements. Computed far-field radiation patterns predict a gain of 2.7 dBi which is in line with previously published results. The validated antenna model was used to investigate the potential detuning effect caused by close proximity objects including a wooden desktop, a conducting bench and a plastic enclosure. Although acceptable performance was found in most cases tested, some conditions caused a significant degradation in performance which may affect the reliability of the communications link. This has important implications for a device designed to be held by a human, and highlights the advantage of modelling the mounted antenna with any conductors or dielectrics which might be placed in close proximity.