Study of the mutual coupling, correlations and efficiency of two PIFA antennas on a small ground plane

The mutual coupling, correlation coefficiency, bandwidth and radiation efficiency are studied for a two PIFA antenna system on a small ground plane. The results show that the mutual coupling in a multi-antenna system can result in low antenna efficiency and higher correlations. Some positions which have less coupling (more than 15dB isolation), low correlation and good bandwidth are found. The correlations are dependent on S₁₁, S₂₁ and S_22; we found that the better matched the antenna gets, the lower correlation it has.