[time-nuts] cordic

Jim Lux jimlux at earthlink.net
Tue Jun 21 14:49:41 UTC 2011

It just came to me..

You're not using CORDIC as a replacement for both the phase accumulator 
and cos LUT, but JUST instead of the LUT, so you ARE doing the "give me 
cos(theta)" on every sample.

So then, it's a trade between a big ROM LUT or a bunch o'gates for 
CORDIC.  And for big N the bunch o'gates is probably going to be easier: 
16 bit phase and wanting 16 bits out would be a 64kbit ROM (assuming you 
didn't do the usual thing of only needing 1/4 cycle)..

I suppose, too, if you're building a digital up/down converter or mixer, 
rather than a LUT feeding a pair of multipliers for I/Q, the CORDIC 
scheme lets you essentially do it on the fly.

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