5 Nov
2003
5 Nov
'03
5:56 a.m.
me wrote:
Steve Harris wrote:
i feel the need to clarify/correct myself: the filters employed are
not chebyshev designs, they were designed the same way as 'unmatched':
frequency response given, iteratively approximate the filter.
they do a lot better than chebys of the same order, but it's quite
impossible to recalculate their coefficients at runtime. if that is
demanded, the polyphase design probably wins easily.
tim
On Sun, Nov 02, 2003 at 10:49:17PM +0100, Tim
Goetze wrote:
i don't have any precise cycle-consumption figures (a good reason to
try the polyphase filters one day) but i seem to remember having
figured that they come at equal or bigger cost for comparable stopband
attenuation. the frequency response is mostly due to the
oversampling filters;
unfortunately i am at a loss for good realtime-compatible design
methods for those. it would well be possible to recalculate them
(chebyshev prototypes) but that would take quite a few cycles, and
knowledge about how to move the ripple/s in a chebyshev design
(anyone?).
Have you tried polyphase filters? I've never used them but I've heard they
are good for oversampling.