LIS2DW internal Anti-Aliasing filter 1. what order of filter is Anti-Aliasing filter? what's the cutoff frequency of attenuation band? What is the attenuation in the stopband?what's sample rate of internal ADC?

[vwu.11]

Backgroud: i'm hardware engineer and work for SKF. we used your Lis2DW in our product to test speed of metro.

Issue: we found some noise siganl or high Freq. aliasing add in collected data in low frequency.

In LIS2DW user guide manual, i find some decriptions about LIS2DW internal blocks.

it says that  lis2dw has anti-Aliasing Filter at the input of ADC in high performance mode. details in attachment. i want know some key points as shown as blew, that are not clearly described .

1. what order of filter is Anti-Aliasing filter? in guide manual, it tell me cutoff frequency of anti-aliasing fiter is 400 Hz. what's the cutoff frequency of attenuation band? What is the attenuation in the stopband?
2. what's sample rate of internal ADC? guide manual just say a parameter of ODR that isn't the sample rate.

[vwu.11]

Anybody answer me? It's urgent for me.

[Eleon BORLINI]

Hi @vwu.1​ ,

Let me try to answer to your question, as far as I can.

Do you know the frequency of the high frequency noise you suspect it is folded inside the LIS2DW band?

1. what order of filter is Anti-Aliasing filter? in guide manual, it tell me cutoff frequency of anti-aliasing filter is 400 Hz. what's the cutoff frequency of attenuation band? What is the attenuation in the stopband? --> The Anti-Alias filter on this device is a 1-st order, with the 3db cutoff frequency at 400Hz. This is different of course from the ODR, the output data rate, which is not fixed at can be configured. The ODR determines a Nyquist frequency of ODR/2 (but always limited to 400Hz). It might be the case that if you are using max ODR and the noise frequency is just after the, you might see something folded in the non-attenuation band.
2. what's sample rate of internal ADC? guide manual just say a parameter of ODR that isn't the sample rate --> The internal ADC is a 12-bit depth ADC, with a sample rate of 3.2kHz.

 

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-Eleon

[vwu.11]

i guess that high frequency noise didn't attenuated as well as we thought because the 1-st order just have -10dB attenutation for signal of outband. and signal amplitue of inband that is valid for us is 0.1g, i think attenutation of outband isn't enough so caues the signal of outband drown out valid signal of inband.

[Eleon BORLINI]

Hi @vwu.1​ ,

so are you measuring an in-band noise above 100mg? Which is the current out-band noise?

-Eleon