RX sensitivity test (S2 and S8) on DUT 2 DUT mode

[Gordon Liu]

Dear Sir,

I'm use 2 nrf52840 chips to test sensitivity by nRF-DTM-1.0 tool.

I find out it's work on 1M and 2M but S8 and S2 can work.

The PER can't get 0% when I only use 25 dB attenuator between 2 DUT ( conducted in the shielding room).

Could you share other  tool to test sensitivity of S8 and S2???

PS: I don't use any equipment(Anritsu, Keysight...) on production.

[Gordon Liu]

Hi,

I have use "DTM tool  of nRf connect 3.6.1".

I find out S8 and S2 still have packet loss 350ea ~100ea when I send 1000 packet.

PS: I use the Lite-point IQXel to capture the signal pattern of a S2 packet.  

[Kenneth]

Can you also try with two DK as shown here?

When using 30byte payload with S2 there will be a packet sent every 1.25ms (when using S8 every 3.125ms), so that means I should receive about 8000 packets in 10seconds when using S2. That seems to be correct here.

[Gordon Liu]

Hi

Thanks for your responses.

I find out the Rx test tool that need more timing accuracy of receive packet.

So, I change the capture pattern (RF signal) that be 100 packets be a pattern file.

I can test S2 and S8 now, but S2 sensitivity less S8 sensitivity  5 dB.  It's not make sense.

Do you have any comment??

And Please share the send time per  a packet  for 1M and 2M (30byte).

 

[Kenneth]

Hi,

From the datasheet I can find sensitivity values:
https://infocenter.nordicsemi.com/topic/ps_nrf52840/radio.html#unique_544454632

Looks like there is a typical 4dB difference between 125kbps(S8) and 500kbps(S2). So that is very close to what you measure of 5dB.

Looks like your measurements are a bit worse compared to datasheet:

Difference 1Mbps datasheet vs. your measurement: 1-2dB
Difference 2Mbps datasheet vs. your measurement: 0dB
Difference 125kbps(S8) datasheet vs. your measurement: 3-5dB
Difference 500kbps(S2) datasheet vs. your measurement: 4-6dB

I think maybe you have some low level noise in the system (e.g. USB) that may impact the lower sensitivity levels here. If the loss was due to cable and connectors I would expect them to influence all measurements. You could for comparison use 2 DK's and a step attenuator between the two DK and see how much attenuation you can have until the packet loss increase to about 30%.

For 1M and 2M they are both 625us when using 30byte payload.

Best regards,
Kenneth