Generating a signal with noise

If you need a random number generator that you can synthesize, then look at this tutorial and code:

http://www.ovro.caltech.edu/~dwh/correlator/pdf/lfsr_tutorial.pdf

http://www.ovro.caltech.edu/~dwh/correlator/pdf/lfsr_tutorial_src.zip

In the code you have above, it looks like you are using a linear feedback shift register (LFSR) to generate your random noise. An LFSR is used to generate a pseudo-random binary sequence (PRBS), but its only one bit of the LFSR that actually has a random characteristic (that is why PRBS has binary in the name). In the code above, you are using the full LFSR register contents, and these are not random. The tutorial shows how you can create a multi-bit output LFSR/PRBS generator (and provides VHDL code to do so).

Cheers,

Dave