Chassis Diversity Antenna Comparison

Chassis models comprising a conducting plate on a PCB are often used for cellphone-type terminals, and the diversity elements are usually inverted-F antennas (IFAs). This paper investigates different chassis-mounted IFA configurations for diversity performance. The IFAs are normally mounted in the corners of a rectangular chassis, but here we include a pair of colinear IFAs on the long edge to clarify the impact of pure spacing (no element rotation). The various configurations have different matching levels and we compare the diversity performance in terms of their isolation rather than their matching. It is shown how rotating the elements (including angular spacing, or polarization diversity, to the linear spacing) gives better overall diversity performance without any introducing extra techniques (cutting slots on the groundplane, de-coupling networks, etc). The use of the electromagnetic isolation reveals the effect of structural isolation on the performance because it effectively eliminates the mismatch factor and the antennas can remain unmatched for a diversity performance comparison.