Modelling of the monopole interaction with a small chassis

The measurement and network modelling of the self- and mutual impedances of a monopole and a flat dipole lead to an over-all equivalent circuit model for the monopole mounted on a small chassis. The transition from the flat dipole as an intermediate step to the rectangular monolithic chassis needs the chassis mode theory. The equivalent circuit gained from the fitting of measurement data for one particular chassis length is shown to reproduce the principle behavior of the monopole bandwidth as a function of chassis length. Improvements of the accuracy of the model can be achieved by a fitting process which applies the equivalent circuit model directly to the impedance measured for the monopole mounted on the chassis.