A transmission line model for the capacitively loaded inverted-F antenna (CLIFA)

Capacitive loading by means of a printed parallel plate element on the edge of an IFA has been used for size reduction. A transmission line model is used herein to provide close form solution for this antenna. The T-line model is based on the asymmetric coplanar waveguide and the capacitive loading is estimated using the parallel plate capacitor equations. The unloaded case is compared to three cases of different capacitive loads which result in different sizes for the radiation element. Circuit model results are compared against simulated and measured data for the reflection coefficient with impedance information obtained from the T-line model. Measured radiation pattern plots are shown for all four cases.