System and method for estimating a signal propagation property of a substance composition in a predefined level range

A radar gauging system for installation at a tank containing a substance composition including at least a first substance having a first density, a second substance having a second density lower than the first density, and a third substance having a third density lower than the second density, the radar gauging system comprising:

• a transceiver for generating, transmitting and receiving electromagnetic signals;
• a vertically extending transmission line probe coupled to the transceiver and configured to guide an electromagnetic transmit signal from the transceiver at least partly through the substance composition and to return to the transceiver an electromagnetic reflection signal resulting from reflection of the transmit signal at one or more impedance discontinuities encountered thereby, the transmission line probe having:
• a first probe portion extending along the transmission line probe between a first probe position defined by an impedance discontinuity at a first distance from the transceiver and a second probe position at a second distance from the transceiver, shorter than the first distance, the first probe portion being configured to provide a first coupling between the transmit signal and the substance composition in a first level range surrounding the first probe portion;
• and
• a second probe portion extending along the transmission line probe between the second probe position and a third probe position at a third distance from the transceiver, shorter than the second distance, the second probe portion being configured to provide a second coupling between the transmit signal and the substance composition in a second level range surrounding the second probe portion, the second coupling being weaker than the first coupling provided by the first probe portion;
• and
• processing circuitry coupled to the transceiver and configured to estimate, based on a timing relation between the transmit signal and the reflection signal and on a known length of the first probe portion, a signal propagation property of the first level range of the substance composition surrounding the first probe portion.