A signal processor for use in association with a frequency analyzer, can operate in the frequency translation mode or the filter mode.The signal processor comprises a first low pass filter, the signal from which is fed to two first parallel programmable gain amplifiers controlled by a first digital function controller. The signals then pass via two, second low pass filters to two second programmable gain amplifiers controlled by a second digital function controller. The signals from the second amplifiers are then added by an adder and filtered by a third low pass filter.The first controller is controlled by a frequency signal equal to the frequency in the middle of the bandwidth being translated and the first filter is controlled by a frequency which is a multiple of the control frequency to the first controller.In the range translation mode, the second filters and second controller have a control signal equal to the bandwidth frequency and the third filter is controlled by a signal which is a multiple of the control signal to the second filter and the second controller.In the filter mode, the cntrol signals to the first and second controllers are equal to each other and the control signals to the first and third are equal to each other.