Page 300 - Phase-Locked Loops Design, Simulation, and Applications
P. 300
MIXED-SIGNAL PLL APPLICATIONS PART 2: FRACTIONAL-N FREQUENCY
SYNTHESIZERS Ronald E. Best 177
Figure 7.12 Noise transfer functions of a third-order ΣΔ ADC. Solid curve: without
compensation. Dotted curve: with compensation by additional poles.
When the oversampling ratio is high (which is the case in most applications) NPG is
approximately equal to the squared noise gain at the Nyquist frequency
(7.19)
The simulations performed by Kuo et al. have shown that the system stays stable whenever
the noise power gain is less than a maximum NPG max . They found an empirical formula for
the maximum noise power gain:
(7.20)
