Modified implementation architecture for sinusoidal frequency modulation is introduced to extract the range information from the Received radar echo. Range ambiguity problem arises because the range is calculated from the estimated phase of the Received signal which is wrapped into (0,2π］. By integrating Doppler frequency shifts, the variation of range can be estimated and used as an auxiliary information to help eliminating the corresponding range ambiguity. The performance of the new technique is evaluated by simulations. The results show that this technique is robust to sever phase noise and can be used effectively for ambiguity elimination of the modified sinusoidal frequency modulated continuous wave radar.