Patent ID: 8223066

Claim:
A radar level gauge system, for determination of a filling level of a product contained in a tank, said radar level gauge system comprising: first pulse generating circuitry for generating a transmission signal in the form of a first pulse train having a first pulse repetition frequency; second pulse generating circuitry for generating a reference signal in the form of a second pulse train having a second pulse repetition frequency, said second pulse repetition frequency differing from said first pulse repetition frequency by a predetermined frequency difference; a propagation device connected to said first pulse generating circuitry and arranged to propagate said transmission signal towards a surface of said product inside the tank, and to return a reflected signal resulting from reflection of said transmission signal at said surface of the product contained in the tank; measurement circuitry connected to said propagation device and connectable to said second pulse generating circuitry, said measurement circuitry being configured to form a measurement signal based on said reflected signal and said reference signal; and processing circuitry connected to said measurement circuitry for determining a value indicative of a filling level based on said measurement signal, wherein said measurement circuitry comprises: a time-correlator for generating a sequence of values, each value representing a time correlation between a pulse of the reference signal and the reflected signal; a first feedback circuit arranged to receive a signal indicative of said sequence of values, said first feedback circuit comprising a feedback loop including a first integrator having a first time constant; a second feedback circuit arranged to receive said signal indicative of said sequence of values, said second feedback circuit comprising a feedback loop including a second integrator having a second time constant being higher than said first time constant; and activation circuitry allowing selective activation of said first feedback circuit and said second feedback circuit.