AWR2944: AWR2944 5MHZ ghost

siyuan.yao

Prodigy 90 points

Part Number: AWR2944
Other Parts Discussed in Thread: LM63625-Q1

Hi expert,

In our new designed board there is a noise in 1D FFT. There frequency is from 4.8750Mhz to 5.1391Mhz.

I tested on board that there is no noise in this range.

Our power supply is LM63625-Q1(2M switch)+LP877451A1RXVRQ1(16MHZ, and 4mhz boost)

Why there is a noise in 1D FFT? Do you have some idea on the rootcause or detection method?

Thanks a lot!

over 1 year ago

0 siyuan.yao over 1 year ago

Prodigy 90 points

Addition information : if we use absorb material to shield only the TX there is no noise. also no noise when only shield the RX.

0 aozer over 1 year ago in reply to siyuan.yao

TI__Mastermind 26925 points

Hello,

What happens with the spur if you increase and decrease the RX gain?

Can you also try enabling individual TX/RX pairs and see if it is happening on all pairs or just certain pairs?

Regards,

Adrian

0 siyuan.yao over 1 year ago in reply to aozer

Prodigy 90 points

Hi Aozer,

Thanks for your support!

We tested decrease the RX gain, noise disapper.

0 siyuan.yao over 1 year ago in reply to siyuan.yao

Prodigy 90 points

what is the cause now?

0 siyuan.yao over 1 year ago in reply to aozer

Prodigy 90 points

Seems the noise is positively related to the RX gain, TX gain, and RCS.

What should be the noise from? It is from antenna design or other circuit on board？

0 aozer over 1 year ago in reply to siyuan.yao

TI__Mastermind 26925 points

Hello,

Is it possible to try feeding the 1V and the 1.8V supplies externally? Something must be coupling into the RF or clock subsystem, the most sensitive place for coupling is through the external supplies.

Also, did you confirm if there is any sensitivity to one of the specific TX/RX pairs? If not, can you try individually enabling the TX/RX pairs and see if it shows up on all pairs or just certain pairs?

Regards,

Adrian

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AWR2944: AWR2944 5MHZ ghost