AWR1642: 77G MMwave radar CISPR25 RE test failed at 2.4GHZ

xiong Jiang

Part Number: AWR1642

We use awr1642 designed 77G mmwave radar product. In RE test with CISP25 spec, it fails @2.4GHZ. See figure as below.

We detected that it's not from power supply. We disabled AWR1642, and make power supply work with resistor load, then the noise disappeared.

Would you please support to detect:

1. where is the noise from?

2. How can we pass the CiSPR25 RE class 5 test.

3. How can we make the noise frequency offset to left a little, to avoid 2.4G HZ limit in CiSPR25 spec.

over 6 years ago

0 Vivek Dham over 6 years ago

TI__Guru 58035 points

Hello,
The 2.4Ghz component could be harmonic of our internal processor clock (600Mhz DSP). By default we pass the emission standards prescribed by ETSI. The CiSPR 25 spec is typically more stringent. Its common for module vendors to use some kind of shield around the chip to reduce the emissions.

Regards,
Vivek

0 xiong Jiang over 6 years ago in reply to Vivek Dham

Prodigy 30 points

Hello,

Thanks for your reply!

I had made a copper shielding on chip, but it doesn't work., noise still exist. Do you have some idea on this phenomenon?

Can I modify the external crystal of chip to make the frequency decrease from 40MHZ to lower value, to make this peak offset to avoid 2.4G limit?

0 Vivek Dham over 6 years ago in reply to xiong Jiang

TI__Guru 58035 points

Hello Xiong,
The shield should not have any big opening , as much as possible it should be enclosed.
The 40Mhz clock frequency can be changed by upto 200ppm, that would be about 480Khz at 2.4Ghz. Would this level of shift help you?

Regards,
Vivek

0 Vivek Dham over 6 years ago in reply to Vivek Dham

TI__Guru 58035 points

Hello Xiong,
Do let us know if the above information about xtal frequency shift helpful to resolve your issue.

Regards,
Vivek

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AWR1642: 77G MMwave radar CISPR25 RE test failed at 2.4GHZ