A phase-domain 2nd-order continuous time /spl Delta//spl Sigma/-modulator for frequency digitization

A PLL based frequency digitizer based on phase domain noise shaping is introduced. It is shown that the digitizer is a second order continuous time delta-sigma modulator operating in the phase domain. The proposed architecture is capable of digitizing the frequency of RF signals with a high degree of precision. This property can be used to digitize and demodulate an FM signal simultaneously. This concept is validated using a practical example based on a wireless standard. The simulation results exhibit a good agreement with the linear analysis. Moreover, benefits and drawbacks of this architecture are discussed and compared with respect to other architectures