Mixed analog-digital correlator using sigma-delta and multirate processing techniques

Describes a mixed analog-digital solution for designing correlators with continuous-time input signals which employs a combination of sigma-delta and multirate processing techniques. Such an architecture can overcome the major limitations of purely analog circuits and still achieve the attractive objectives of low power consumption and small chip size which cannot be afforded using purely digital signal processing techniques together with the associated data conversion circuits. In the mixed-signal analog-digital architecture considered, the high-speed output bit stream of a sigma-delta modulator is used to control the operation of a switched-capacitor decimator. The multiplication itself is accomplished in the charge domain and is followed by an appropriate filtering function and sampling rate reduction. Computer simulations were carried out to confirm the suitability and correct design of the proposed architecture for power extraction of signals with highly degraded signal-to-noise ratio