Precision Level Measurement using VNA based Radar Interferometry

The radar-based technique has been proven to monitor liquid levels without direct contact. Measuring levels in industrial tanks with sub-millimeter accuracy requires more operating bandwidth, leading to critical transceiver design with signal processing challenges. This experiment demonstrates real aperture radar interferometric techniques for sub-millimeter level change measurement. The experiment utilizes VNA (Vector Network Analyser) instrument as an SFCW (Stepped Frequency Continuous Wave) radar source for conducting ranging experiments, and a metallic water tank of 2m height with 0.6m diameter is used. The temporal phase information is exploited from the backscattered radar signal to estimate the change in the water level in the tank. An experiment with different volumetric quantities, i.e., 5 ml, 20 ml, and 500 ml of water, was added to the tank, and the change in the water level of the order of the submillimeter was measured. The significance of using the 1-dimensional phase unwrapping method for unambiguous measurement is also demonstrated.