Two Operating Frequencies using Half-Duplex

Hi there,

I was wondering if anyone knew whether the LimeSDR USB board can be to receive and transmit frequencies on two different frequency bands. Please note, we would not need to receive two different frequencies at the same time. We are hoping to use the LimeSDR as a ground station transceiver for a CubeSat mission. Simply put, our intended usage for mission data downlink passes would look something like this (again, none of these steps are happening concurrently, one after another).

  • Receive payload data on 2400MHz
  • Transmit confirmation response over 438MHz
  • Receive confirmation response over 438MHz.

Basically, it would be our hope that the LimeSDR could accept two receiving frequencies at different instances during an overhead satellite pass. It would only transmit on one frequency on the other hand.

If anyone had any insight on this topic, I would be incredible appreciative of your thoughts/experiences!

All the best,

LimeSDR USB is 2x2 MIMO, but the receive channels have a shared LO and those two downlink frequencies are far apart, so you’d have to retune between receiving 2400MHz/438MHz.

May be easier to just use 2x LimeSDR Mini, with one permanently tuned to 2.4GHz for payload downlink and the other to 438MHz for confirmation Tx/Tx.

Thank you for your feedback!! We weren’t aware of the shared LO. Just to expand on your answer a bit further - would it be possible to program the limeSDR to retune itself to the two frequencies between each pass? So, one pass it would receive entirely on 2400MHz, then in the interim before the next pass (approximately 85-90 minutes), the LO would switch to 438MHz based on a programmed sequence or schedule, which could then be altered depending on our operations?

It sounds like we can’t be going between the two frequencies during a pass, but is the LimeSDR able to change its LO frequency indirectly - via programming through the FPGA possibly?

Thank you once again for your comments!


Don’t have figures to-hand, but re-tuning is pretty fast and so it may be possible to do this during a pass, if you don’t need to receive on both frequencies simultaneously and depending upon how quickly this would need to be done. Note that this and all other setup is done via the Lime Suite API, else another abstraction, such as SoapySDR. So control is via software on the attached host and not by programming the FPGA. E.g. see: