Decimation Filter (FIR) Output

[Eminent.Engineer]

Hello Everyone

I am designing a Decimation Filter for Delta Sigma ADC, the input to ADC is 3 KHz 0.5V peak to peak (0.25V to -0.25V) Sine wave but the output of Decimation Filter (3367 taps FIR Low Pass Filter) is 3 KHz sine wave but the amplitude in the range of 0.507 to -0.507. How I should convert this value to equivalent voltage ? Can someone suggest what could be the problem with Decimation Filter implementation ?

Thanks in advance.

 

[FvM]

A very unclear question, I fear. You would primarly specify the ADC's DC transfer characteristic and secondly a filter characteristic. For the latter, you need to know output smapling frequency, cut-off frequency, filter characteristic.

 

[Eminent.Engineer]

Just to simplify the unclear question,
After Decimation I have got the output actually it will be a binary output (ENOB ~11 bit) but in MATLAB it is decimal value, how to convert this output to equivalent voltage ? Input Voltage range is 0.25 to -0.25 V.

 

[FvM]

It's essentially the same as with the input value. It involves a scale factor. I presume that you can calculate the scale factor from the given filter transfer characteristic.

 

[Eminent.Engineer]

Hello FvM

I have attached the time domain and frequency domain response of Low Pass Filter. Can you elaborate a bit about "scale factor from the given filter transfer characteristic", any reading material related to this issue will be appreciated.

Thanks for your timely responses.