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LORA sensitivity deteriorate in presence of signals of other frequency

We are using SX1262 trans-receiver in our design for lora and our operation frequency is 865MHz-867 MHz. Our sensitivity is around -139 dbm in normal cases and reception is fine. But when the module is exposed to signals of the frequency (any 100 Mhz to 1000Mhz) our reception halts. Exposed signal strength is 3V/m. It is showing RSSI around -70 in presence of exposed field but not reception of valid packet. We believe that sensitivity of transceiver is deteriorating in presence of external field. Our design is near to base reference design.
Avatar
Hi,

Could you confirm the modulation of the interfering signal?
Do you observe a flat, -70dBm reported RSSI, irrespective of the input frequency, from 100 MHz to 700 MHz for instance?

best regards
Namste,
Good to see you are replying in such tough situation worldwide. Hope you are fine.

1) Interfering signal is Amplitude modulated. Instantaneous RSSI reads in range of -70 to
-80 at 100 MHZ to 864 MHz of interfering signal. When interfering signal frequency is
equal to centre frequency it shows instantaneous RSSI in range of 0 to -10.

2) We have conducted experiments by keeping LORA module in continuous receiving
mode.
a) When Lora signal strength is good receiver receives packet with RSSI around -80 and
SNR +4(interference signal is not present). If we apply interference signal in this
condition then packet received shows RSSI around -70 to -80 and SNR drops to -20

b) When Lora signal strength is poor receiver receives packet with RSSI around -100
and SNR -18 to -20(interference signal is not present). If we apply interference signal
in this condition then no packet received and instantaneous RSSI is shown -70 to -80

Thanks

Avatar
Hello,

It looks like you device under test is picking up a lot ; I find it weird though that the "coupling" is flat across the frequency range...

To me, this looks like AM detection. Could you confirm the modulation depth and frequency of the sine wave modulating the interferer? With this, we could experiment shifting the IF.

Rgds
Depth of modulation is 80 % and carrier frequency is 1 KHz.

Experiments we are conducting is as per EMC Standard of Radiated susceptibility (IEC-61000-4-3) in GTEM cell.

Our observation is SNR deteriorates when exposed to interfering Signal.

Our LORA setting is BW 125 KHz, SF 12, CR: 4/5.

Would you suggest any tests we could conduct at our end
Reg
Prasanna
Depth of modulation is 80 % and carrier frequency is 1 KHz.

Experiments we are conducting is as per EMC Standard of Radiated susceptibility (IEC-61000-4-3) in GTEM cell.
Our observation is SNR deteriorates when exposed to interfering Signal.
Our LORA setting is BW 125 KHz, SF 12, CR: 4/5.

Would you suggest any tests we could conduct at our end?
Reg
Prasanna
Depth of modulation is 80 % and carrier frequency is 1 KHz.

Experiments we are conducting is as per EMC Standard of Radiated susceptibility (IEC-61000-4-3) in GTEM cell.
Our observation is SNR deteriorates when exposed to interfering Signal.
Our LORA setting is BW: 125 KHz, SF: 12, CR: 4/5.

Would you suggest any tests we could conduct at our end?
Reg
Prasanna
Avatar
Can you try with an unmodulated interfer (turn off AM), at the same level and on a single (failing) frequency?
That would help verify the assumption

Rgds
We will do that and revert. Unfortunately we can do it after couple of week as INDIA is lock down till 14th Apr.

Just to add information. We conducted some field trials and observed Nodes near to Cell 4G phone towers has similar issue. We can see frequent communication stalling in nodes near to cell phone towers.