Yes, if g1*g2 = 1 there comes the function.
I'm wondering how to define the Gains of the modulator. Someone use the way that make (suppose the equation is B.Y(z)=...) B=1 to get the Gains (g1 g1 ...), it's simple for 2nd-order SD modulator, but more complicated for high order modulator. And the Stability is concerned with the Gains. Chapter 2.3.2.1 'Stability considerations' --the stability of 2nd-order modulator of Fig 2.7 is guaranteed if g2'/(g1g2)>1.25. Can anybody explain me the relation of Stability and Gains clearly for 2nd-order and high order ?
Thx.