A processor implemented method for optimum channel selection in a twin radar with a first channel and a second channel, the method comprising the steps of: receiving a time domain signal reflected from a subject being monitored, by each of the first channel and the second channel respectively; filtering, by a low pass filter, the time domain signal received by each of the first channel and the second channel respectively, to obtain a filtered time domain signal having frequencies less than a predetermined frequency corresponding to restful breathing associated with the subject being monitored; simultaneously computing, via one or more hardware processors, a peak to peak value ( A PP 1) of an autocorrelation function of the filtered time domain signal associated with the first channel and the second channel respectively, for a predefined time window; and an average value ( V PP 1) of peak to peak amplitude of the filtered time domain signal associated with the first channel and the second channel respectively, for the predefined time window; and selecting, via the one or more hardware processors, at least one of the first channel and the second channel as the optimum channel based on the computed peak to peak value of the ACF and the average value of the peak to peak amplitude of the filtered time domain signal, wherein the optimum channel reproduces a fundamental frequency, wherein signal of the optimum channel will be more autocorrelated than a null channel and wherein if the second channel has a higher periodicity and auto correlation function than the first channel, then the second channel is chosen as the optimum channel. receiving a time domain signal reflected from a subject being monitored, by each of the first channel and the second channel respectively; filtering, by a low pass filter, the time domain signal received by each of the first channel and the second channel respectively, to obtain a filtered time domain signal having frequencies less than a predetermined frequency corresponding to restful breathing associated with the subject being monitored; simultaneously computing, via one or more hardware processors, a peak to peak value ( A PP 1) of an autocorrelation function of the filtered time domain signal associated with the first channel and the second channel respectively, for a predefined time window; and an average value ( V PP 1) of peak to peak amplitude of the filtered time domain signal associated with the first channel and the second channel respectively, for the predefined time window; and a peak to peak value ( A PP 1) of an autocorrelation function of the filtered time domain signal associated with the first channel and the second channel respectively, for a predefined time window; and an average value ( V PP 1) of peak to peak amplitude of the filtered time domain signal associated with the first channel and the second channel respectively, for the predefined time window; and selecting, via the one or more hardware processors, at least one of the first channel and the second channel as the optimum channel based on the computed peak to peak value of the ACF and the average value of the peak to peak amplitude of the filtered time domain signal, wherein the optimum channel reproduces a fundamental frequency, wherein signal of the optimum channel will be more autocorrelated than a null channel and wherein if the second channel has a higher periodicity and auto correlation function than the first channel, then the second channel is chosen as the optimum channel.