Theory and experiment of planar inverted F-antennas for wireless communications applications

The planar inverted F-antenna (PIFA) is a compact element for wireless applications. There is little theory available on this subject. This dissertation investigates simple theoretical models for two most popular types of PIFA – rectangular and semicircular PIFA’s. The PIFA’s three–slot cavity model (CM) and transmission line model (TLM) are presented here, along with numerical and physical experimental techniques and results for the PIFA far field and impedance behavior. The CM is used to predict PIFA’s far field pattern, polarization, impedance, Q-factor, and bandwidth from an equivalent resonant cavity with perfect magnetic and electric boundaries. The TLM represents the PIFA as an equivalent transmission lines arrangement with three branches representing its radiating slots and one short-circuited branch. Extensive measurements and numerical simulations confirmed that PIFA’s radiation and impedance characteristics can be predicted with simple theoretical calculations described here. Measurements also showed PIFA’s pattern and impedance dependence on the sideslot radiation.