AWR1642: AWR1642's phase noise

user3683377

Part Number: AWR1642

Hi，

I just saw a post about phase noise in TI E2E Community. The link is below

https://e2e.ti.com/support/sensors/f/1023/t/744318?tisearch=e2e-quicksearch&keymatch=AWR1642%20PHASE%20NOISE

I don't understand this sentence"For most of the close in signal coupling of TX to RX signal the phase noise component will almost cancel out since the down conversion at the RX also happens using the same LO as the TX. Hence we get the gain of the phase noise cancellation and the SNR is mostly limited by the noise figure of the RX chain."

Could you explain it in more detail?

Why the phase noise leakge signal component will almost cancel out?

And in our system We also found in our AWR1642 radar system that the phase noise is higher than the noise floor, How can we reduce the phase noise?We tried adjusting the parameters of the PLL, but found no registers to configure.

Thanks and regards.

over 6 years ago

0 Cesar over 6 years ago

TI__Guru**** 150344 points

Hi

Will have to check with person who provided this answer

Thank you
Cesar

0 Vivek Dham over 6 years ago in reply to Cesar

TI__Guru 58035 points

Hello Wendong,
The way the FMCW radar system works is the same LO is used in the transmit and receive chain. When the down conversion happens on the receiver with the same LO there is a correlation benefit seen on the phase noise which depends on the delay between the TX to Rx signal and the frequency offset from the LO. So for very small delay (direct coupling from TX to Rx) and low frequencies there is a large correlation benefit. You can find online material about this. One such reference is the following paper: apps.dtic.mil/.../a303432.pdf

Regards,
Vivek

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AWR1642: AWR1642's phase noise