Mathematical modelling of heated rear-window antennas

Vehicle heated rear window or backlite antennas are in use for the reception of VHF/UHF radio signals. At these frequencies the interaction of the antenna and the vehicle plays a crucial part in determining receiving system performance. In the past the design of these antennas has been carried out by empirical methods. The paper describes the use of the moment method modelling to predict the antenna performance. This offers advantages over empirical design in that antenna performance can be optimised without access to the actual vehicle. Measurement of radiation patterns presents some practical difficulties in this frequency band, particularly at high elevation angles. The system is required to operate in urban and rural areas which can lead to fading and multipath propagation. This means that the antenna radiation pattern must be free of nulls to quite high elevation angles. Mathematical modelling of radiation patterns allows predictions to be made at all angles