A system for processing a radar signal for deriving a Doppler frequency from a sampled digital input signal radiated from a frequency modulation continuous wave (FMCW) radar, the system comprising: a transmission module configured to repeatedly transmit a radar signal having a unique frequency variation and a pulse repetition interval; a variation module configured to vary the frequency variation or the pulse repetition interval of the radar signal transmitted from the transmission module; a receiver for receiving the transmitted radar signal according to a frequency variation or a pulse repetition period, the transmitted radar signal being reflected by an object to be detected before received by the receiver; an extraction module configured to extract an interference signal from the received radar signals when interference occurs between the received radar signal and another radar signal; and an adjustment module configured to adjust the received radar signal to reduce the extracted interference signal; characterized in that the extraction module is configured to calculate a cumulative histogram for the sampled digital input signal converted from the received radar signal and extracts the interference signal from the calculated cumulative histogram by selecting a threshold and taking a signal exceeding the threshold as the interference signal, wherein the extraction module is further configured to calculate the cumulative histogram by taking an absolute value of the sampled digital input signal, accumulating the absolute value, and then generating and accumulating a profile of an entire digital input signal by comparing an accumulated square value with a reference value, such that the threshold being selected through a power series for a value corresponding to a particular rate in the cumulative histogram from which the sampled digital input signal is calculated. a transmission module configured to repeatedly transmit a radar signal having a unique frequency variation and a pulse repetition interval; a variation module configured to vary the frequency variation or the pulse repetition interval of the radar signal transmitted from the transmission module; a receiver for receiving the transmitted radar signal according to a frequency variation or a pulse repetition period, the transmitted radar signal being reflected by an object to be detected before received by the receiver; an extraction module configured to extract an interference signal from the received radar signals when interference occurs between the received radar signal and another radar signal; and an adjustment module configured to adjust the received radar signal to reduce the extracted interference signal; characterized in that the extraction module is configured to calculate a cumulative histogram for the sampled digital input signal converted from the received radar signal and extracts the interference signal from the calculated cumulative histogram by selecting a threshold and taking a signal exceeding the threshold as the interference signal, wherein the extraction module is further configured to calculate the cumulative histogram by taking an absolute value of the sampled digital input signal, accumulating the absolute value, and then generating and accumulating a profile of an entire digital input signal by comparing an accumulated square value with a reference value, such that the threshold being selected through a power series for a value corresponding to a particular rate in the cumulative histogram from which the sampled digital input signal is calculated.