Jitter generation compare to dithering
in [DSP]
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From: Jerry Avins on 9 Nov 2009 12:14 BCLIM wrote: > Hi Eric, > Sorry for that it's not clear. I'm interested to know the method > to generate the jitter and later inject it into a system in order to check > the jitter amount change due to the system. Basically if I have the syste > clock and would like to generate a jitter signal relative to the system > clock and inject this in to another system. > Thanks. Maybe someone cleverer can devise a more elegant way. but I would filter the system clock to approximate a sine wave, then square it up again by feeding it into a comparator with bipolar output. Noise injected along with the signal or into the reference input will produce jitter on both edges of the clock. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Eric Jacobsen on 9 Nov 2009 13:58 On 11/8/2009 5:53 PM, Randy Yates wrote: > Eric Jacobsen<eric.jacobsen(a)ieee.org> writes: >> [...] >> This place is going to get really tiresome if every response to a >> question has to include every possible nuance in the answer. > > To make a statement that is not true in general but only in certain > special cases and not point out that it's only true in those special > cases is not a "nuance," in my opinion. I don't think I did that. Perhaps you did, but it likely doesn't matter. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
From: Eric Jacobsen on 9 Nov 2009 14:01 On 11/8/2009 6:33 PM, Jerry Avins wrote: > Eric Jacobsen wrote: >> On 11/8/2009 9:07 AM, wazerface(a)gmail.com wrote: >>> On Nov 7, 6:02 pm, Eric Jacobsen<eric.jacob...(a)ieee.org> wrote: >>>> On 11/7/2009 12:56 PM, Greg Heath wrote: >>>> >>>>> On Nov 5, 1:04 am, "BCLIM"<boonchun_...(a)yahoo.com> wrote: >>>>>> Hi, >>>>>> I have a doubt on jitter generation. Wonder is the method to generate >>>>>> jitter signal is that same as dithering generation method? >>>>>> Understand that >>>>>> both are usign random signal generation with different >>>>>> distribution. For >>>>>> example, triangular, rectangular etc. >>>>> I always thought that for a signal defined over a finite length of >>>>> time, >>>>> jittering added a randomness to the amplitude whereas dithering >>>>> added a randomness to the starting time. >>>>> Hope this helps. >>>>> Greg >>>> I think it'd help for the OP to clarify what he means by his >>>> terminology. In my experience jitter usually means random fluctuation >>>> in period, (usually sampling period), while dithering usually means >>>> adding small random values to an input to reduce quantization noise. >>>> >>>> It's also not clear whether the OP is asking about unintentional or >>>> intentional jitter. Some clocking systems add jitter in order to >>>> reduce spurious emissions related to the clock frequency. Is that the >>>> topic of the question? >>>> >>>> -- >>>> Eric Jacobsen >>>> Minister of Algorithms >>>> Abineau Communicationshttp://www.abineau.com >>> >>> My understanding is that dithering doesn't reduce quantization noise >>> (power) in general, but de-correlates it. >> >> Yes, and the decorrelation allows an increase of SNR with appropriate >> filtering, so it can be used to effectively reduce quantization noise. >> But you're right, dithering by itself doesn't reduce quantization noise. > > But it can increase resolution if one has the luxury of averaging > measurements. > > Jerry That was exactly the point, yes. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
From: Jerry Avins on 9 Nov 2009 15:52 dbd wrote: ... > So there exist neural net folks who made sloppy use of signal > processing terminology too. Is that supposed to be a surprise to > anyone? Not really, but it is an unfortunate circumstance. (They should have called it "jiggle".) Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Jerry Avins on 9 Nov 2009 16:01
Eric Jacobsen wrote: > On 11/8/2009 6:33 PM, Jerry Avins wrote: >> Eric Jacobsen wrote: >>> On 11/8/2009 9:07 AM, wazerface(a)gmail.com wrote: >>>> On Nov 7, 6:02 pm, Eric Jacobsen<eric.jacob...(a)ieee.org> wrote: >>>>> On 11/7/2009 12:56 PM, Greg Heath wrote: >>>>> >>>>>> On Nov 5, 1:04 am, "BCLIM"<boonchun_...(a)yahoo.com> wrote: >>>>>>> Hi, >>>>>>> I have a doubt on jitter generation. Wonder is the method to >>>>>>> generate >>>>>>> jitter signal is that same as dithering generation method? >>>>>>> Understand that >>>>>>> both are usign random signal generation with different >>>>>>> distribution. For >>>>>>> example, triangular, rectangular etc. >>>>>> I always thought that for a signal defined over a finite length of >>>>>> time, >>>>>> jittering added a randomness to the amplitude whereas dithering >>>>>> added a randomness to the starting time. >>>>>> Hope this helps. >>>>>> Greg >>>>> I think it'd help for the OP to clarify what he means by his >>>>> terminology. In my experience jitter usually means random fluctuation >>>>> in period, (usually sampling period), while dithering usually means >>>>> adding small random values to an input to reduce quantization noise. >>>>> >>>>> It's also not clear whether the OP is asking about unintentional or >>>>> intentional jitter. Some clocking systems add jitter in order to >>>>> reduce spurious emissions related to the clock frequency. Is that the >>>>> topic of the question? >>>>> >>>>> -- >>>>> Eric Jacobsen >>>>> Minister of Algorithms >>>>> Abineau Communicationshttp://www.abineau.com >>>> >>>> My understanding is that dithering doesn't reduce quantization noise >>>> (power) in general, but de-correlates it. >>> >>> Yes, and the decorrelation allows an increase of SNR with appropriate >>> filtering, so it can be used to effectively reduce quantization noise. >>> But you're right, dithering by itself doesn't reduce quantization noise. >> >> But it can increase resolution if one has the luxury of averaging >> measurements. >> >> Jerry > > That was exactly the point, yes. I'll add that the averaged points needn't be of a supposedly stationary value. In measuring weight gain per unit time (is there a name for that?) in a very noisy environment, I computed a linear regression to get the average slope of 54 measurements and was able to calculate the present time intercept (IOW, the current weight) to about a quarter of a LSB. Incidentally, old fogies like me whose feet suffer some numbness are better able to keep their balance with vibrators in their shoes. That gives new meaning to "jitterbug". Jerry -- Engineering is the art of making what you want from things you can get. ����������������������������������������������������������������������� |