Generating high order PDM bitstreams

[Losing]

Hello, I am studying BISTs of Delta Sigma Modulators, and I am trying to generate pulse density modulated bitstreams. I've started off using the algorithm mentioned in this wikipedia article . However, this algorithm is first order and I would really like to improve this by using a second or even higher order algorithm. It seems that I can accomplish this by using more samples' errors worth of feedback, as mentioned in this wikipedia article . So I guess my question is, does anyone have experience doing this, or know of a resource that could point me in the right direction? Perhaps there is a spice model of a Delta Sigma Modulator that I could use in MatLab or Cadence that would allow me to do this. Or perhaps a Labview vi capable of generating the bitstreams. The bitstreams need to represent single frequency analog signals.

[Wingfeather]

Hi Losing,

This page has some excellent information on delta-sigma modulation. The "DSM Introduction" (top of the third table) is a really nice introduction to the process and takes you through the derivation of both single-stage and MASH-type topologies.

He also has some MATLAB scripts (which I haven't looked at, but which I would expect to be good). They might do what you want, or be easily modifiable to do so.

[Losing]

Thanks! That is exactly what I was looking for.