Modelling vehicular diversity antenna using loads on parasitic elements

Switched parasitic antennas are known to alter the radiation of a feed antenna. In this paper, we use computer modelling and measurements to demonstrate that radiation pattern diversity for the FM band at 100 MHz can be obtained by switching the load on a parasitic antenna placed in close vicinity of the feed antenna on an automobile. This configuration only requires one feed cable and a single amplifier. In addition, a pin diode controlled by a single wire is used to switch between loads on the parasitic antenna. This significantly reduces the cost of the system when compared to a 4 antenna diversity system and there is the potential that it can be used in small sized apertures. The simulations were verified by measurements on a real car or a scaled models whenever possible. A finite integration based software, CST Microwave Studio, was used to model and simulate the antenna on the car.