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AWR1843BOOST: why HPF1 and HPF2 cannot remove antenna coupling (DC and very low frequency)?

William Gao
Intellectual 630 points
Part Number: AWR1843BOOST

Hi,

I am using the AWR1843Boost and DCA1000 to capture data and use matlab to make post processing. With Range FFT, every time I found there is very strong amplitude near the zero range. That should be the antenna coupling. However, I noticed that there are HPF1 and HPF2 default combination in mmwave studio to remove the low frequencies. I don't quiet understand why there is still the Tx coupling near the zero range, shouldn't it be removed by HPF?

Thanks,

Williiam

  • 0
    TI__Guru 58035 points

    Hello William,

    You are right that that is mostly Tx to Rx antenna coupling. The HPF provide large attenuation to the very low frequency signals, but not infinite attenuation. With good isolation of 30dB you will still see a -15 to -20dBm input on the Rx port. So even a 60 dB attenuation from the filters would still show a signal of -80dBm, which is high enough to observe but is low enough to avoid any kind of saturation on ADC.

    The intention of the HPF is only to avoid the signal being high enough the saturate the ADC, once  that is achieved we don't think the remainder of the signal should be an issue.

    Regards,

    Vivek