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Continuous-wave (CW) homodyne radar has been the most commonly used architecture for physiological monitoring, due to its ease of implementation. This chapter shows the simplified block diagram of a physiological radar, indicating radio frequency (RF) front-end, baseband, and signal processing modules. It examines specific challenges related to each of those modules. The chapter describes the single-channel system limitations. Since a quadrature receiver system and the two orthonormal output signals enable to measure the relative phase information accurately, it is used in various applications, including digital communications and Doppler radar. The chapter also describes arctangent demodulation with DC offset compensation to combine quadrature outputs. It presents relevant quadrature receiver theory and arctangent demodulation with center tracking DC compensation method. Experimental results demonstrating that center tracking is suitable for demodulation of small and large displacement are presented.