#### tigger

##### Newbie level 5

**decimation filter**

How do I implement a fractional interpolation/decimation filter in hardware? I know how to do an integer interpolation/decimation filter (by using polyphase filters), but don't know how to do a fractional one without overspeed. For example, to convert 100MHz sampled data to 90MHz, the decimation factor is 10/9. Mathematically it can be done by 9x interpolation followed by 10x decimation, but that means 9x overspeed, or 900MHz clock for the polyphase filters. Can this be done using only 100MHz clock?

Thanks.