A level gauge system, for determination of a filling level of a product contained in a tank using electromagnetic signals, said level gauge system comprising: transmission signal generating circuitry for generating an electromagnetic transmission signal in the form of a sequence of transmit pulses; a propagation device connected to said transmission signal generating circuitry and arranged to propagate said electromagnetic transmission signal towards a surface of said product inside the tank, and to return a reflected electromagnetic signal resulting from reflection of said electromagnetic transmission signal at said surface of the product contained in the tank; reference signal providing circuitry configured to provide an electromagnetic reference signal in the form of a sequence of reference pulses; timing circuitry connected to the transmission signal generating circuitry and the reference signal providing circuitry for providing a time-varying phase difference between the electromagnetic transmission signal and the electromagnetic reference signal, said time-varying phase difference varying between a phase difference corresponding to a minimum measurement distance and a phase difference corresponding to a maximum measurement distance during a measurement sweep time period; measurement circuitry connected to said propagation device and to said reference signal providing circuitry, said measurement circuitry being configured to provide a measurement signal based on said electromagnetic reference signal and said reflected electromagnetic signal; processing circuitry connected to said measurement circuitry for determining a filling level based on said measurement signal; and power management circuitry connected to at least one of said transmission signal generating circuitry and said reference signal providing circuitry, characterized in that said power management circuitry is configured to control at least one of said transmission signal generating circuitry and said reference signal providing circuitry to change from a low-power state to a high-power state at a start of a continuous reduced time period corresponding to a plurality of said transmit pulses, said reduced time period comprising a time when said time-varying phase difference corresponds to an anticipated filling level and to change back from said high-power state to said low-power state at an end of said reduced time period, said reduced time period being shorter than said measurement sweep time period, said reduced time period being determined based on a previously determined filling level. transmission signal generating circuitry for generating an electromagnetic transmission signal in the form of a sequence of transmit pulses; a propagation device connected to said transmission signal generating circuitry and arranged to propagate said electromagnetic transmission signal towards a surface of said product inside the tank, and to return a reflected electromagnetic signal resulting from reflection of said electromagnetic transmission signal at said surface of the product contained in the tank; reference signal providing circuitry configured to provide an electromagnetic reference signal in the form of a sequence of reference pulses; timing circuitry connected to the transmission signal generating circuitry and the reference signal providing circuitry for providing a time-varying phase difference between the electromagnetic transmission signal and the electromagnetic reference signal, said time-varying phase difference varying between a phase difference corresponding to a minimum measurement distance and a phase difference corresponding to a maximum measurement distance during a measurement sweep time period; measurement circuitry connected to said propagation device and to said reference signal providing circuitry, said measurement circuitry being configured to provide a measurement signal based on said electromagnetic reference signal and said reflected electromagnetic signal; processing circuitry connected to said measurement circuitry for determining a filling level based on said measurement signal; and power management circuitry connected to at least one of said transmission signal generating circuitry and said reference signal providing circuitry, characterized in that said power management circuitry is configured to control at least one of said transmission signal generating circuitry and said reference signal providing circuitry to change from a low-power state to a high-power state at a start of a continuous reduced time period corresponding to a plurality of said transmit pulses, said reduced time period comprising a time when said time-varying phase difference corresponds to an anticipated filling level and to change back from said high-power state to said low-power state at an end of said reduced time period, said reduced time period being shorter than said measurement sweep time period, said reduced time period being determined based on a previously determined filling level.