dpll VS dspfilters

For an example of a simple digital PLL that you could modify for this purpose, check out this article discussing this logic.

Are you interested in an all-digital solution? If so, I have a couple of digital PLL's you might want to check out. These are the PLL's I use if I want to demodulate a digital signal in hardware, as demonstrated by this example. If what you are looking for is a mixed digital/analog solution, then ... I don't have an example.

Have you considered this article? It goes over the basics of the autocorrelation function, while also illustrating how you can build one with a Wishbone interface. Further, the Verilator logic for this function is kept and maintained on github here. Sure, it uses Wishbone. If you want to use AXI you can either use a bridge, or rework the the interface (it's not that hard ...).

I marked as "both" above, but one might argue that my "hobby" designs are more "Internal Research and Development" (IR&D) than just hobby. Everything has a purpose. Today's hobby design may be used in tomorrow's paying project. Examples include the both the ZipCPU and its subcomponents, my AXI work, DSP filters, PLLs, FFT and much more--all of which have found their way into a variety of customer designs.