“From an electronic module on top of the tank, a sensor oscillator sends down a linear frequency sweep, at a fixed bandwidth and sweep time. The reflected radar signal is delayed in proportion to the distance to the level surface. Its frequency is different from that of the transmitted signal, and the two signals blend into a new frequency proportional to distance.”This new frequency can then be used for accurate determination of fluid level.
The major benefit of employing FMCW technique for level measurement in a tank is that the signals transmitted are frequency modulated i.e. FM instead of amplitude modulated i.e. AM signals. Now, the major part of noise in a tank falls in the AM range which does not influence the FM signals. Hence, FMCW happens to be the only system which can be suitably used for meeting high accuracy requirements of tank gauging.