Wi-Fi RF characteristics are not stable over temperature variations

espola
Posts: 7
Joined: Thu Feb 02, 2017 4:31 pm

Wi-Fi RF characteristics are not stable over temperature variations

Postby espola » Thu Oct 05, 2017 7:55 am

Hello,
when testing RF tx characteristics at different temperatures we see that the output power and EVM values drift out of spec.
Ambient temperature changes and/or heavy RF activity will cause this. We test temperatures from -40C to +85C.

If the device is reset RF calibration is done and characteristics are ok again.

This behavior is seen in the attached screen dumps from measurements. At -40C the
the instrument can't even recognize the signal/data rate.

Normal room temperature, good signal:
NINA-W131 #311 Wi-Fi Char 54Mbit 25C.png

Low temperature, bad signal:
NINA-W131 #311 Wi-Fi Char 54Mbit -40C.png

Low temperature after reset, good signal:
NINA-W131 #311 Wi-Fi Char 54Mbit -40C (after reset).png

For the test we use the test commands:
fcc_mode_sel 2
wifitxout 6 0xc 12 (channel 6, data rate 54Mbps, Attenuation 3dB)

Is there any way run the calibration periodically or automatically when temperature changes.
Can calibration be initiated from the application?

Best regards,
Ola
Attachments
NINA-W131 #311 Wi-Fi Char 54Mbit -40C.png
-40C before reset
NINA-W131 #311 Wi-Fi Char 54Mbit -40C.png (219.81 KiB) Viewed 473 times
NINA-W131 #311 Wi-Fi Char 54Mbit -40C (after reset).png
-40C after reset
NINA-W131 #311 Wi-Fi Char 54Mbit -40C (after reset).png (219.63 KiB) Viewed 473 times
NINA-W131 #311 Wi-Fi Char 54Mbit 25C.png
25C
NINA-W131 #311 Wi-Fi Char 54Mbit 25C.png (208.41 KiB) Viewed 473 times

ESP_Sprite
Posts: 1214
Joined: Thu Nov 26, 2015 4:08 am

Re: Wi-Fi RF characteristics are not stable over temperature variations

Postby ESP_Sprite » Fri Oct 06, 2017 3:18 am

Fyi, most engineers still are on holiday here... We'll look into this after the weekend.

WiFive
Posts: 1203
Joined: Tue Dec 01, 2015 7:35 am

Re: Wi-Fi RF characteristics are not stable over temperature variations

Postby WiFive » Fri Oct 06, 2017 5:32 am

What hardware are you testing? Wroom32 module?

ESP_Faye
Posts: 17
Joined: Thu Dec 10, 2015 6:47 am

Re: Wi-Fi RF characteristics are not stable over temperature variations

Postby ESP_Faye » Thu Oct 12, 2017 11:56 am

Hi,

Sorry that the problem does exist, because the RF test firmware has no periodic calibration function, it is a continuous package mode.

The SDK has periodic calibration functions that are not affected by temperature.

Currently the periodic calibration interface does not exist in the RF test firmware. But we will provide it in the future after verification.

Thanks for your interest in ESP32!

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