Precise microwave measurement of liquid level

A simple interferometric waveguide setup has been developed, enabling for precise distance measurement of liquid level. Total reflection from the liquid surface is not necessary. For the most common case of lossy liquids, reflection phase must be determined properly. This may be accomplished by the use of a waveguide short for calibration. The setup was tested in measurement of water level. Resolution of the order of micrometers was achieved in X-band.