Is sampling 2x50 MHz possible with 2 synchronized LIMESDRs

Dear All,
The LMS7002M has RF bandwidth limitations.
Lets say I have a 80 MHz @ 900 MHz wide signal and want to digitize it. I know that with a single LIMESDR that it is not possible.
What if we have 2 LIMESDR’s in RX only Mode,
one centered at 875 MHz, digitizing the Signal between 850-900 MHz,
and the other centered at 925 MHz, digitizing the Signal between 900-950 MHz,
At the end the obtained I&Q values will be mixed in an FPGA.
Is this a pipedream or is this doable?

Perhaps 4x4 MIMO LimeSDR-QPCIe might be of interest:

@Zack / @ignasj, would this meet the stated requirements?

Actually what I am trying to do is like doubling the possible sampling rate, something like an interleaved ADC LIMESDR style.

Several things to consider, assuming that you really want to keep two LimeSDR boards synchonized for that application:

  • In order to keep frequency synchronization between devices, you will have to use external ref inputs on boards and feed them with common reference signal (e.g. 10 MHz)
  • If you want to keep time synchronization between two devices during operation, it may be problematic, as noone has successfully implemented 1 PPS-based time synchronization for LimeSDR so far. So your application may require transmitting some known signal, which could then be “heared” by both devices and then used to extract relative time offset between them, before receiving actual signal of interest.
  • Also, you will suffer from aplitude and phase differences in signals received from both devices, which may cause problems during integration of this signals.

Hi @booth,

Well, you may try to utilize NCOs. If your band of interest is 860MHz - 940MHz, then tune RxPLL (SXR) to 900MHz, set channel A NCO to down-convert and frequency to 20MHz while channel B NCO to up-convert and frequency to 20MHz.

There is also still unsolved problem of ADC synchronization.

I did not know that was possible. That makes 80 MHz of sampling on a single LIME7002m (2 RX channels combined). However the datasheet states that the LIMELIGHT I/F has a bandwith of 60 MHz?
Can anyone clarify?