Page 294 - Phase-Locked Loops Design, Simulation, and Applications
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MIXED-SIGNAL PLL APPLICATIONS PART 2: FRACTIONAL-N FREQUENCY
SYNTHESIZERS Ronald E. Best 174
Figure 7.9 Signals of the ΣΔ ADC. (a) Signal U at the output of the integrator. (b) Output
i
U of the quantizer. (c) The error sequence e(nT ).
Q
The transfer function G(z) of the integrator has been given in Eq. (7.6). When n integrators
are cascaded, the transfer function of the series connection of integrators becomes
(7.12)
n is also called the order of the system. For this type of ΣΔ ADC, the signal and noise transfer
functions are as follows:
(7.13)
(7.14)
