Using LimeSDR to test Low/High/Band pass/stop filters

[mzs]

@ccsh

It is possible, though you’ll need additional hardware (directional coupler or RF bridge, possibly calibrated noise source as well).

I don’t know, I can see a simple configuration to test basic filters, which would require minimal additional hardware:

First sweep:
LimeSDR_TX->20dB attenuator->LimeSDR_RX
reconfigure hardware for second sweep:
LimeSDR_TX->20dB attenuator->Filter under test->LimeSDR_RX

A CW signal transmitted by LimeSDR_TX sweeping over the required frequency range in sync with the LimeSDR_RX tuning over the same frequency range.
If you took the difference between the two set of measurements you would be measuring the relative attenuation and cancel out, or at least minimise, any gain or phase nonlinearities in the TX and RX path.