Broadening the bandwidth in terminal antennas by tuning the coupling between the element and its ground

The intensive research on terminal antennas in recent years examined new ideas that resulted in the formulation of guidelines on how specific antenna parameters could be accomplished. Among the more challenging variables in obtaining parameters, two gained our particular attention: a broad bandwidth and a radiation pattern that does not produce SAR values exceeding the permissible level. Broadening the bandwidth at the lowest resonance in multiresonant antennas featuring the highest possible scale of miniaturization was the most difficult task. Owing to the possible highest scale of miniaturization, various modifications of PIFAs have attracted much attention. We present an equivalent circuit model for a dual-band antenna. The model reflects the importance of a strong mutual coupling in miniaturized PIFAs. Providing very broad bandwidths with highly miniaturized antenna was possible when parts of the PIFA element were inserted into the slits in the small ground plate. The measured efficiency values are high and meet the expectations of modern wireless device designers.