Mark Borgerding wrote:> Jerry Avins wrote: > >>Rick Lyons wrote: >> >> ... >> >> >>>Am not sure that I have added much to the discussion here. >> >> >>You have. You just told me that I was calling a CIC is a Hogenauer >>filter. I owe Mark an apology for the grief I subjected him to. >> >>Jerry > > > Not at all. I appreciate the exchange. It helps me explore and test my > beliefs and understanding. > > I'm never 100% sure about anything I think I know, not even my uncertainty. > > > -- Mark > > > PS. I hope your granddaughter is doing well.She attended a PBA ceremony last week (accompanied by the nanny, of course) to honor the cops who helped save her. Everybody looked happy. It was televised and in the NY Daily News. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
CIC filter question
Started by ●January 17, 2006
Reply by ●January 21, 20062006-01-21
Reply by ●January 23, 20062006-01-23
>AAA wrote: > > ... > >> Hi, it is Alex. >> >> May be I caught the idea about how unsaturation property of two's >> complement arithmetic work: I think it relies upon not using in >> calculations multiplications by not hole coefficients (divisions), whatis>> the case in CIC-filters. Because they may reflect not present atadders>> (and regs) m.s.b.'s to the calculated sum. >> >> But I d'nt know any paper with explanation of this in details (how CIC >> integrators overflowed by DC and low frequences in the signal banddoes>> work correctly). Tell me please one. May be anybody knows where I cansee>> Hogenauer's article? > >http://www.phptr.com/articles/article.asp?p=361985&seqNum=1 and its >sequels will interest you. In particular, for overflow matters, >http://www.phptr.com/articles/article.asp?p=361985&seqNum=2 > >Jerry >-- >Engineering is the art of making what you want from things you can get. >����������������������������������������������������������������������� >Hi, Jerry! Will you explane me please also how CIC stages pruning is possible ("11.4.2.2. Down sampling CIC" in the article)? I think if initial stages have less bit-length accumulators there will be errors in calculations in overflow condition, but if all accumulators will have the same length - it will not. Isn't it? The Author of this article takes into account the maximum output values of respective integrators, but DC or low frequency will overflow them at all at any bit-length. Thank you. Alex.
Reply by ●January 23, 20062006-01-23
AAA wrote: ...> Hi, Jerry! > > Will you explane me please also how CIC stages pruning is possible > ("11.4.2.2. Down sampling CIC" in the article)? I think if initial stages > have less bit-length accumulators there will be errors in calculations in > overflow condition, but if all accumulators will have the same length - it > will not. Isn't it? > > The Author of this article takes into account the maximum output values of > respective integrators, but DC or low frequency will overflow them at all > at any bit-length.Overflow doesn't hurt as long as the accumulator is long enough to hold the final number, and each input alone. Try some small numbers and see. An overflow bit is simply discarded. A two-bit overflow from one operation isn't possible if the conditions I stated are met. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●January 25, 20062006-01-25
>AAA wrote: > > ... > >> Hi, Jerry! >> >> Will you explane me please also how CIC stages pruning is possible >> ("11.4.2.2. Down sampling CIC" in the article)? I think if initialstages>> have less bit-length accumulators there will be errors in calculationsin>> overflow condition, but if all accumulators will have the same length -it>> will not. Isn't it? >> >> The Author of this article takes into account the maximum output valuesof>> respective integrators, but DC or low frequency will overflow them atall>> at any bit-length. > >Overflow doesn't hurt as long as the accumulator is long enough to hold >the final number, and each input alone. Try some small numbers and see. >An overflow bit is simply discarded. A two-bit overflow from one >operation isn't possible if the conditions I stated are met. > >Jerry >-- >Engineering is the art of making what you want from things you can get. >����������������������������������������������������������������������� >Hi, Jerry! Is CIC pruning some kind of compromise between calculation errors an filter complexity? Or decimating CIC filter with DC at the input (signal to measure) may be pruned without any risk of errors at all? Alex.
Reply by ●January 25, 20062006-01-25
AAA wrote: ...> Is CIC pruning some kind of compromise between calculation errors an > filter complexity? Or decimating CIC filter with DC at the input (signal > to measure) may be pruned without any risk of errors at all?By pruning, I assume you mean adjusting the size of successive accumulators to save silicon. If the accumulator is wide enough 1) so that no input can cause more than one bit to overflow, and 2) to hold the final answer, there will be no error at all. With DC input and enough integration time, condition (2) won't be met. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
