Assume multiplying 20bits data a[19:0] with 2.0.
Generally, we realize it as {a[18:0], 1'b0}.

However I find {a[18:0], a[0]} in digital single loop Delta-Sigma Modulator for Fractional-N Synthesizer.
http://m.eet.com/media/1055785/mingliang-fig6.gif

I tried simulation.
But I can't find out any remarkable difference of noise shaping characteristics between them.

What effect can we expect by {a[18:0], a[0]} instead of {a[18:0], 1'b0} ?

carlgrace wrote on Oct 3^rd, 2014, 3:29pm:
Thanks.