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AWR1843: Anti-aliasing Filter in AWR1843

Ali AAK
Prodigy 180 points
Part Number: AWR1843


Tool/software:

Hi,

I read another conversation related to my question in this link:

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1459777/awr1843aop-understanding-hpf-behavior-in-awr1843aop-for-ghost-object-mitigation?tisearch=e2e-sitesearch&keymatch=anti-aliasing%20%22awr1843%22#

the datasheet of AWR1843 mentioned these two sentences in page 29 of it:

  • "Less than ±0.5 dB pass-band ripple/droop"
  • "Better than 60 dB anti-aliasing attenuation for any frequency that can alias back into the pass-band."

Cesar mentioned in conversation of above link, "These parameters are related to the digital baseband and not the HPF.".I'm confused about this. Anti-aliasing filter should be before ADC and couldn't be after ADC and in digital chain. Because it should reduce low ADC Rate effects that make aliasing. So Anti-aliasing filter should be before ADC in order to reduce frequencies more than 0.5*ADC Rate (Nyquist).

please Help me.

Thanks

  • 0
    TI__Guru**** 150294 points

    Please give me some time to check with the design team

    thank you

    Cesar

  • 0 in reply to Cesar
    TI__Guru**** 150294 points

    Hi

    I have received additional information from the design team:

    The digital filter comes after the ADC in the RX chain. It adds ~+/-0.5dB ripple to the IF passband response, but has a sharp cutoff at ~0.9*sample rate. The anti-aliasing comment is meant more for signals that are falling outside the upper edge of the IF passband to prevent them from folding back into the IF passband after going through the digital filter.

     

    The IFA, which drives the ADC, also has a passband response, and this is used as an anti-aliasing filter as well prior to the ADC.

     

    Thank you

    Cesar