ENOB increase using the FIR Compiler

[stevet]

Hi

I am using FIR Compiler 7.2 to create a FIR filter and decimation.  The input to Filter and Decimation is 24 bits wide, the decimate reduces the sample rate by a factor of 6.  Since you achieve a 1 bit increase for a factor of 4 over-sampling my new bit length should be 26 bits, am i correct in assuming this?

Should i then set my output width to 26bits and select one of the output rounding modes using the configuration GUI?

Steve

[meherp]

FIR performs the multiply and add operation, therefore your output width depends on the 'filter coefficient' width and "input singal" width.

You can check the full scale width for the above values in the FIR IP as well. It will give you both the total width and the fractional width. Based on fractional width, we can decide the total number of bits. For example if total output width is 12 and fraction width is 7. Then we can set total width from 5 (i.e. no decimal after rounding) to 12 (i.e. full scale output)