A measuring instrument for measuring a signal (101) having a first partial signal and at least a second part signal has a high frequency processing means (25), which is adapted to mix the signal (101) to an intermediate frequency signal (103) and this into a digital total signal digitizing (104). The meter further has a digital mixer (18), which is designed to generate by shifting the frequency of the digital total signal (104) a first digital total measurement signal (107a) and a second digital total measuring signal (107b). The meter has in addition to a digital filter (19) which is adapted to the first digital total measurement signal (107a) to a first digital measurement signal (108a) and the second digital total measuring signal (107b) to a second digital measuring signal (108b) filter.