Removal of surface-wave induced radiation nulls for patch antennas integrated with vehicle windscreens

A solution to the problem of radiation nulls for patch antennas integrated with vehicle windscreens is presented. The nulls, attributable to surface waves within the windscreen superstrate, are removed by the addition of a thin resistive film to the windscreen surface. Analysis of the surface-wave modes at 5.8 GHz within two typical laminated windscreen structures coated with a resistive film shows a sheet resistance value of 50 /spl Omega//sq to be appropriate. Polar-pattern results demonstrate the effectiveness of the technique in removing the radiation nulls without significantly reducing the forward gain.