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define a filter kernel (with floating-point numbers) in vhdl

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Hi


can any one say about this problem in my thesis

How i should define a fir filter kernel with floating point number like "- 0.0144" in vhdl wich could be synthesized(synthesizable)?

Mahmoodreza_62(at)yahoo.com
 

You'll most likely want to use fractional numbers rather than floating point for the FIR coefficients and fixed point arithmetic for the filter.
 
Re: define a filter kernel (with floating-point numbers) in

coul you explain more,how i should use them?
 

Re: define a filter kernel (with floating-point numbers) in

First you have to select a number range and bitwidth for the coefficients. Assuming it would be -1...+1 and 16 bit, you convert the parameter constant to signed integer by multplying it with 2**15. E.g. for -0.0144 you get -472. All filter multiplications are performed as integer multiply then. The coefficient LSB actually represents 1/(2**15).
 
hi
i have another problem,plz help!

in this code :
sum <= sum+image()*filter()

which all of them are integer image is a matrix of integer range 255 downto 0,filter is integer array range 2**16-1 downto -(2**16),sum is integer range 2**24-1 downto -(2**24)

but i have problem in range of sum because overflow is happen

i don know how i should define the range of sum?!!!
 

Where does the overflow happen?

the integer type can store any value from -2**31 up to 2**31-1

for your own sanilty, you may want to stop using integers and use the new fixed point libraries from IEEE. Then you dont need to keep track of any numerator/fraction in any number, its all taken care of. You could do something like this:

signal filter : sfixed(2 downto -8 ); --covers the range -8 to +(8- 2^-8 ) in steps of 2^-8 (0.00390625)
 

HOW SHOULD I use this librarary?

from where i can dl it? after dl where is the destination folder in modelsim?
 

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