Slot antenna measuring speeor route surface of vehicle - has perforated plate modifying radiation pattern of downwardly directed prim. horn mounted ahead of front wheel

摘要

The unit (2) installed, e.g. under the front spoiler or bumper of a private car, consists of a primary horn (12) and a horizontal plate (13) symmetrical about the same axis. The size and arrangement of holes in the plate contribute to the chosen radiation pattern. The spherical or piecewise-plane wavefronts fall on the plate which may be either plane or domed. Similarly a Fresnel lens may be formed to produce a plane sec. wavefront. USE/ADVANTAGE - Antennae of uncritical efficiency can be mfd. very easily and cheaply to be esp. insensitive to contamination, whether used on lorry, car or tracked vehicle. Esp. for measuring speed and/or quality of road or track, e.g. stony or slippery, ice on rails. Therefore suitable for regions having extremes of climate and vehicles used in construction works and agriculture.