A tank level sensor based on Six-Port technique comprising a quasi-TEM waveguide

Robust tank level monitoring is an important issue in chemical and process industry and a challenging task if high accuracy has to be reached. The proposed sensor structure consists of a quasi-TEM mode waveguide on the one hand and an interferometric Six-Port receiver structure on the other hand. The waveguide structure itself in combination with the liquid to be monitored acts as a reflection phase shifter. By superposing the reflected and the transmitted electromagnetic wave within a passive structure, the relative phase between both signals can be accurately obtained by means of the Six-Port principle. Thus, a change of the liquid level is directly related to the relative phase shift monitored by the Six-Port interferometer. In contrast to antenna based tank level sensors, the hereby presented system concept makes use of a novel waveguide structure. Therefore, it is not sensitive to multi-target scenarios and multipath propagation.