CIC fixed point representation

Guys,

I'm somehow new to simulink. I'm trying to design a programable CIC From reading, you should design @ the highest decimation ratio then you choose output according to programable decimation ratio.

My problem is that I do not understand the fixed point notation. For example my CIC output WL=14/FL=5 and I need to divider by :

• 2^3 for decimation ratio = 4
• 2^5 for decimation ratio = 8
• 2^7 for decimation ratio = 16

I need the output width to be 11 bits as I'm going to implement this as VHDL later. I knew that I should add a convert block after CIC to have my new data widths. Now I can not calculate the WL/FL for the three cases above.

Answer 1

[Ganesh Gaonkar]

Did you check if this block can help ? : cicdecimation

To know more about it's usage, you can try to go to the demo 'dspddc' which is about 'GSM Digital Down Converter'