Resin-housing effects on the resonant frequency of handsets with built-in antenna

The effects of resin-housings on the resonant frequencies of built-in antennas in handsets were investigated. A resin plate was adopted as a model for a resin-housing and was located close to a PIFA that was mounted on a rectangular metal plate (125 by 35mm²). The size of the PIFA was determined such that the resonant frequency became 2GHz. Variations in the resonant frequency were monitored when the permittivity (epsiv_r), the thickness (t) of the resin plate and the distance (s) between the resin plate and the PIFA were varied. The results indicate that a reduction of 6.8% in the resonant frequency could be achieved in the case where epsiv_r = 3, t = 1mm and s = 0mm. In this case, the measured results were confirmed to be in good agreement with the calculated results. Furthermore, it was found that miniaturization of 36% could be achieved by positioning a resin plate adjacent to the PIFA.