Principle of rear windscreen car antenna

The heated rear windscreen car antenna is being increasingly used for reception purposes, as a means of avoiding the mechanical problems which may arise with rod antennas. The objective in its design is not, however, to find an optimum geometric shape for printing on the rear windscreen, but rather to use the existing heater-demister as an antenna. Two problems arise in such a design. One is the matching problem over the wide frequency range from long waves to VHF, and the other is the electromagnetic solution to the geometry of the heater-demister.<>