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Message ID: 6045     Entry time: Tue Nov 29 22:19:26 2011
Author: Den 
Type: Update 
Category: digital noise 
Subject: straight line 

 I tried to understand what part of the signal is corrupted while passing through a digital straight line without any filters. From here we can figure out what precision is used.

I analysed coherence between C1:SUS-MC3_LSC_EXCMON and C1:SUS-MC3_LSC_OUTMON without any filters between them. 

real_coherence.jpg

I did the simulation in Matlab using single and double precision. Basically, I took a random signal, made some operations with it to obtain some digital error:

signal1 = randn(1e6, 1);          signal2 = randn(1e6, 1);         signal3 = signal1+signal2;          signal4 = signal3 - signal2;

Then I plotted coherence between signal1 and signal4 that are actually the same signal but signal4 has some digital error. This was done both for single (left red plot) and double (right blue plot) precision.

float_coherence.jpg        double_coherence.jpg

From here we make a conclusion that C1:SUS-MC3_LSC_EXCMON and C1:SUS-MC3_LSC_OUTMON has single precision. The signal might be converted from double to single in the dtt tools but if dtt works with double precision then the problem is with signals.

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