The present paper addresses the problem of contactless respiration monitoring system realization based on continuous wave radar (CWR). The developed system is composed of two parts, hardware and software parts. In hardware part, the main purpose is to realize a CWR by using low cost components. The software part is dedicated to develop algorithms for drawing the breathing rhythm and estimating the respiration frequency. Firstly, the received signal is processed and its phase is exploited in the estimation of the respiratory rhythm. Secondly, the respiratory frequency is estimated based on either the periodogram method, the autocorrelation method or on the combination of both methods. Numerical simulation, together with an experimental study have shown the efficiency of the proposed solution in estimating the respiratory rhythm and frequency.