A signal up-conversion system is described. The system comprises a signal input for receiving an input signal to be up-converted; an oscillator system for generating an up- conversion signal having a selectable frequency; a mixer coupled to the input and to the oscillator, for combining the input signal and the up-conversion signal and to generate an up-converted signal; at least two filters, each of the at least two filters having different filtering characteristics; a signal output; a switch system configured to couple one of the at least two filters into a signal path between the output of the mixer and the signal output; and a controller configured to control a frequency of the up-conversion signal and a filter of the at least two filters coupled into the signal path by the switch system. A method switching between up-conversion frequencies is also described.