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SX1280 maximum ranging capability

Semtech Transceivers SX128x family
#1

Hello,
I have implemented a Ka band receiver for small satellites/cubesats in LEO orbit (450-600km) which integrates, after the downconversion to 2.4 GHz, an SX1280 chip for the demodulation of Lora signals.

I wonder if it is possible to exploit the ranging function in LEO, obviously assuming the sufficient link margin to establish communication between satellite and ground station and doppler compensation.

Is there a physical limit value in km? (maybe due to latency?!)

Thank you
Best regards
-Federico

#2

The maximum range with the standard SX1280 @12dBm is going to be circa 100km, with a small yagi on the ground and an omni at the remote.

Bear in mind that both master and slave manage the switch between TX and RX modes and antenna sharing for the packet exchange internally. Which implies that adding additional circuits\devices in the RF path will need some thought.

#3

Thank you,

the hypothetical scenario is a Ground Station with SX1280 as IF Transmitter (so purely TX) followed by an upconverter to, for example, 28 GHz. Typical 10W BUC are used with 2.4m dish.

Satellite receiver has its own low noise downconverter from 28 GHz to IF, where SX1280 is set as pure RX.

Link budget is not a problem in this hypothetical scenario.
There is plenty of C/N for a LoRa communication.

Theoretically speaking, ranging is possible?
Is it only a matter of link budget/margin, or there are other implementation variables such as maximum allowed propagation delay?

Thank you

#4

There will be a limit, of sorts, the ranging results register returns a 32 bit value, not sure what that equates to in terms of distance.

If there are any other restrictions then you will need towait for Semtech to answer.

As for whether what you are attempting is possible, I dont know. The normal operation is that the master TXs the ranging request, then turns around into RX mode ready for the response. The Slave is listening in RX mode and when it receives the ranging request turns around into TX mode and sends the response which the master then receives. This does not seem to fit well with the master being TX only and the slave being RX only.