A method of operating digital signal processing, DSP, unit which suppresses intermodulation noise in a radio frequency, RF, signal detector, said signal detector comprising: - at least one analog-to-digital, ADC, converter having a defined bandwidth of input signal to be converted, - at least two signal generators, each producing local oscillator, LO, signal where each LO frequency range is divided into segments with the provision that each segment is not wider than the corresponding ADC bandwidth and where each segment is represented by its segment center frequency, - at least two RF signal mixers that down-convert the RF signals, using the above said LO signals, into intermediate frequency, IF, signals, - at least one RF frontend circuit whose role is to receive the input RF signal and amplifies it to a level appropriate for mixing by the dedicated RF signal mixer, - a digital signal processing unit with its memory and program logic that controls the signal generators and sets their LO signals, - optionally, a signal combiner and a signal splitter, and - one or more signal amplifiers, and one or more signal filters for removing the produced harmonics of a mixing process, where each RF input signal is processed by the corresponding RF frontend circuit, and optionally combined in the signal combiner with other RF signals, the obtained RF signal is consecutively down-converted; firstly by the signal mixer using LO signal obtained from the first signal generator, then optionally processed through the signal splitter into two branches that are processed differently, from which one resulting signal is again down-converted by the signal mixer using LO signal obtained from the second generator, resulting in the baseband signal that is then converted in the corresponding ADC to a digital baseband signal which is fed to a DSP unit, that is processing the digital signal and communicating with the user, said method being characterized in that the LO frequencies of said signal generators are set by said program logic stored into the DSP unit to form the pair of frequency segments centers out of a union of all possible segment pairs which gives desired sum frequency of desired down-conversion, where said segment pair is known by the DSP unit to produces least intermodulation noise in the detector caused by crosstalk between LO signals and components of said detector, and where the intermodulation noise for every possible LO generators segment pair of complete LO ranges has been measured beforehand and prestored into the memory of the DSP unit. - at least one analog-to-digital, ADC, converter having a defined bandwidth of input signal to be converted, - at least two signal generators, each producing local oscillator, LO, signal where each LO frequency range is divided into segments with the provision that each segment is not wider than the corresponding ADC bandwidth and where each segment is represented by its segment center frequency, - at least two RF signal mixers that down-convert the RF signals, using the above said LO signals, into intermediate frequency, IF, signals, - at least one RF frontend circuit whose role is to receive the input RF signal and amplifies it to a level appropriate for mixing by the dedicated RF signal mixer, - a digital signal processing unit with its memory and program logic that controls the signal generators and sets their LO signals, - optionally, a signal combiner and a signal splitter, and - one or more signal amplifiers, and one or more signal filters for removing the produced harmonics of a mixing process, where each RF input signal is processed by the corresponding RF frontend circuit, and optionally combined in the signal combiner with other RF signals, the obtained RF signal is consecutively down-converted; firstly by the signal mixer using LO signal obtained from the first signal generator, then optionally processed through the signal splitter into two branches that are processed differently, from which one resulting signal is again down-converted by the signal mixer using LO signal obtained from the second generator, resulting in the baseband signal that is then converted in the corresponding ADC to a digital baseband signal which is fed to a DSP unit, that is processing the digital signal and communicating with the user, said method being characterized in that the LO frequencies of said signal generators are set by said program logic stored into the DSP unit to form the pair of frequency segments centers out of a union of all possible segment pairs which gives desired sum frequency of desired down-conversion, where said segment pair is known by the DSP unit to produces least intermodulation noise in the detector caused by crosstalk between LO signals and components of said detector, and where the intermodulation noise for every possible LO generators segment pair of complete LO ranges has been measured beforehand and prestored into the memory of the DSP unit.