SLOT ANTENNA

摘要

An antenna (10) in a radar level gauge for determining the level of the surface (6) of a medium (2) stored in a tank (1). The antenna (10) has a first (11) and a second (13) electrically conductive layer, and between the conductive layers (11, 13) a dielectric layer (12). The second (13) of the conductive layers is provided with a number of holes (14) in a predetermined pattern. Leading to the centre of the dielectric layer (12) is a transmission line (15). The microwaves from a radar unit (3) in the radar level gauge are supplied to the dielectric layer (12) in the antenna (10) via the transmission line (15) and transmitted out in a radial direction from a feed point in the dielectric layer that acts as a waveguide. Via said holes (14) in the second conductive layer (13) a microwave beam radiates out. Due to matching of the phase of the microwave and the placing of the individual holes (14) in the pattern that the holes form, a predominant waveguide mode of the desired order is obtained.