FFT output?

[Altera_Forum]

This is probably going to be a simple question, but have been unable to find documentation to explain it. I'm running a 512 point 24 bit width data streaming FFT. My output is 24 bits with 6 bits of exponent. 

 How is the data being represented? Is it floating point?  How can i convert it to 32 bit floating point?  Thanks,  Ben

[Altera_Forum]

Normally, FFTs on FPGAs would be done in fixed point. If this is the case then exponent is the wrong word to use. 

 Fixed point numbers are just unsigned/signed integers offset by 2^n. In this case, with 24 bits, 6 magnitude (I assume) then this number represents 0-64 (or -32 to (just under) +32) with an accuracy to the nearest 2^-18.  it could still be a floating point, but I doubt it. Fixed point offers very good accuracy but sacrifices the range of data. But as it is basically just all integers it can be done very easily.

[Altera_Forum]

The altera documentation states it uses block floating point for the FFT.  

 so what your saying is, and if my data is x"DEADBE" with an exponent "011100" (28 or -4) than it would shift my value down by 4? and my signal would be x"DEADB.E"   sorry im a little confused, not sure if that makes sense.

[Altera_Forum]

--- Quote Start ---  The altera documentation states it uses block floating point for the FFT.   so what your saying is, and if my data is x"DEADBE" with an exponent "011100" (28 or -4) than it would shift my value down by 4? and my signal would be x"DEADB.E"   sorry im a little confused, not sure if that makes sense.  --- Quote End ---    It might actually be floating point then, just with an 6 bit exponent and 17 bit mantissa instead of the standard 8/23. This reduces logic requirements on the chip. It basically sacrifices range and accuracy so that it uses less resources (and possibly clock faster too).