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SX1268 problem in Rx continuous mode

Hi!

I have problems with receiver sensitivity on SX1268 + TCXO at 433Mhz. The problem appears in LoRa Rx continuous mode and with any SF and BW values. The decrease in sensitivity occurs due to the operation of another closely located radio transmitter on an adjacent frequency. It can be the transmitter of another radio module, walkie talkie or car radio alarm. The decrease in sensitivity occurs by approximately 25-30dBm and is fixed (freezes) even after turning off the radio transmitters. The sensitivity is restored only after restarting the SX1268 receiver. In the GFSK Rx continuous mode on the SX1268 chip and in the LoRa Rx continuous mode on the SX1276 chip, the problem does not appear.

To simulate this problem:

  1. Switch the SX1268 to LoRa Rx continuous mode, BW_125, SF_10, 433.100Mhz, Rx Boosted gain.

  2. Display the RSSI value with constant updating (for example, the value will be -120dBm).

  3. Turn on another radio transmitter at a frequency of 433.300 five times with a duration of two seconds and a pause of one second. The distance between transmitter and receiver is 1 meter.

  4. Change the frequency of another radio transmitter to 433.500Mhz and repeat.

  5. Change the frequency of another radio transmitter to 433.700Mhz and repeat.

5 Change the frequency of another radio transmitter to 434.000Mhz and repeat.

At some point, the receiver sensitivity will decrease by about 25-30dBm and the RSSI value will remain constant at -95dBm even after the transmitter is turned off. The sensitivity is restored only after restarting the SX1268 receiver. This problem will manifest itself at other frequencies of the receiver and transmitter.

I think the problem in SX1268 is related to RF AGC gain. I ask to solve the problem with the sensitivity of the SX1268 in LoRa Rx continuous mode.

Thanks.

Forum thread with a similar problem:
“SX1262 reduced RX sensitivity / packet reception fails”
date:Feb 1 '21
The problem really exists.
The SX1262 reduces the receiver sensitivity for strong out-of-band signals. Sensitivity is not restored even after the out-of-band signal is turned off. Sensitivity is restored after restarting the SX1262 receiver.
This problem does not appear on the SX1276 chip.