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AWR1843: There is a fix 4MHZ noise in radar

user6340460
Prodigy 60 points
Part Number: AWR1843
Other Parts Discussed in Thread: LP87702,

Hi TI experts,

There is a fix 4MHZ noise in radar. 

In the test, if RADAR is in shielded chamber, or forward to sky where is no target, there is no fake target(noise@4M). But if put a reflector front of the RADAR, there will be a 4MHZ fake target.

The PMIC is LP87702, The switching frequency is 4MHZ. I'm not sure whether it is caused by this device.

Can you share some information to solve the fake target of 4MHZ? thanks!

  • 0
    TI__Mastermind 31680 points

    Hello User,

    Could you confirm you are using the PMIC 1.8V to generate the 1V RF supply and 2.3V to generate the analog 1.8V supply?
    In general, you need to isolate the PMIC layout and supply lines from the critical analog circuitry on the AWR device like the XTAL lines, 1v4_APLL and 1v4_SYNTH lines. You could also add additional filtering like LC filters on the supply lines to filter the 4Mhz ripple.

    Also, due to year end holidays, our responses might be delayed. Sorry for the inconvenience caused.

    Wishing you a very Happy New Year!

    Regards,

    Ishita

  • 0 in reply to Ishita Kochar
    Prodigy 60 points

    Hi Ishita,

    PMIC ouput 1.8V & 1.24V to AWR1843. 1.24V step down to 1.0V by a LDO, and supply to AWR1843. All power supply followed by a 0.1uh&10uf LC filter.

  • 0 in reply to user6340460
    TI__Guru 58035 points

    Hello ,

    The 4Mhz spur would most likely be coming due to either insufficient filtering of the power supplies to remove the switching frequency ripple, or there could be coupling of the supply node prior to the filtering onto the sensitive nodes or AWR device as pointed out by Ishita.

    regards,

    Vivek