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FXAS21002 gyro group delay versus ODR and lowpass filter setting

Question asked by Jon Brunetti on Dec 14, 2015
Latest reply on Dec 31, 2015 by Jon Brunetti

Hi,

 

I would like to know the group delay of the FXAS21002C for a given ODR (output data rate) and lowpass filter shown in Table 33 on page 39 of the data sheet. 

 

For example, at 400Hz ODR, Table 33 has the following entries for the lowpass filter bandwidth:

 

Table 33. FXAS21002C LPF Cutoff Frequency

BWODR = 400Hz
0b00128
0b0164
0b1x32

 

 

The group delay likely increases by 2x for each 2x decrease in the LPF (lowpass filter) cutoff frequency. Also the group delay likely increases by 2x for each 2x decrease in the ODR setting.  Therefore, the group delay for any value in Table 33 would be highly useful.

 

If the z-transform of the lowpass filter and the sample rate before decimation is known, that would also answer the question.  For example, if a moving average filter is used as the lowpass filter (sometimes called a SINC filter), knowing the sample rate and filter length, prior to decimation to the ODR, would allow the group delay to be calculated.

 

Thanks in advance for your replies.

 

Jon

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