Time/Frequency

I doubt this has anything to do with ADC slewing, it's still a linear system with a low pass transfer function. 
One idea might be to have a replica of the decimation filter fed with a synchronized pulse that is slowly updated in amplitude and time- shift to minimize the error between the actual signal and the model. The RBJ comb filter idea might work but if the desired small signal is also periodic with the pulse rate then the comb might take that out as well. 
But with a ratio of 1e5 it's going to be a pretty tough job. A lot depends on how fast that pulse drifts around , because with that kind of snr even a small amount of variation will cause the spectrum of the pulse to spread into the desired signal spectrum. 

Bob

On Friday, December 13, 2013 5:20:57 PM UTC, Vladimir Vassilevsky wrote:
> There is an input of strong pulse closely followed by useful small 
> 
> signal. Strong pulse initial amplitude is ~1e5 times that of signal; 
> 
> however it falls exponentially to essentially zero in duration of ~5 
> 
> samples of ADC.
> 
> 
> 
> I need to measure the signal; ignoring preceding strong pulse.
> 
> Time point where the strong pulse ends and the useful signal starts is 
> 
> known.
> 
> 
> 
> Problem: input is sampled by delta-sigma ADC. Therefore strong pulse is 
> 
> smeared over ~16 samples by delta-sigma internal lowpass FIR filter, so 
> 
> it gets superposed with useful signal.
> 
> 
> 
> Is there a way to separate signals after ADC ?
> 
> 
> 
> Vladimir Vassilevsky
> 
> DSP and Mixed Signal Designs
> 
> www.abvolt.com

No, you're screwed. Unless you can get a second sensor somewhere.

Vladimir Vassilevsky wrote:

> There is an input of strong pulse closely followed by useful small
> signal. Strong pulse initial amplitude is ~1e5 times that of signal;
> however it falls exponentially to essentially zero in duration of ~5
> samples of ADC.

Sounds familiar, see NMR spectroscopy.

> I need to measure the signal; ignoring preceding strong pulse.
> Time point where the strong pulse ends and the useful signal starts is
> known.

This is good. You can gate the input of the ADC while the pulse is active, 
using the signal which creates the pulse in the first place as input to the 
ADC gate. Or - if this is not feasable - use some relatively simple electronic
circuit to transform the pulse into a gating signal.  

bye
Andreas
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