An 80 GHz radar level measurement system with dielectric lens antenna

In this contribution, a Frequency Modulated Continuous Wave (FMCW) radar system, working in the 75 to 85 GHz frequency range, for level measurement of liquids in tanks is presented. The realized radar antenna has been specially designed to cope with the given harsh environmental conditions (high pressure, high temperature, explosion protection requirements, etc.) in industrial applications. The basic design concept of the antenna is to utilize a dielectric lens as `barrier element' between the tank and the radar electronics module, and especially for high-pressure applications, a cylindrical glass element is included into the lens system. Different configurations of dielectric lens antennas (different biconvex and plano-convex lenses with 45 mm diameter), also in versions including a glass barrier element with 20 mm thickness, have been evaluated by means of electromagnetic field simulations and measurements. A circular waveguide with 2.6 mm inner diameter equipped with a conical horn with 4.8 mm diameter and 3 mm length is used as feeding structure. Results demonstrate a range pulse width (-6 dB) of 30 mm with the full bandwidth of 10 GHz of the system. As expected, the best antenna performance is given with the biconvex lens antenna without the glass barrier element. Nevertheless, a reasonably good performance in the case of equipping the glass barrier with plano-convex dielectric lenses at its front and rear sides can be achieved.