I'm trying to perform some receive system fault finding, and I'd like to understand how the sig_gen extension works a bit better.
Where exactly does it inject the signal into the Kiwi ?
Is it an actual RF signal injected into the antenna port before the LPF, or is it a bit further down the chain ?
Does it actually make use of the ADC, or is it routed internally in the FGPA simulating an ADC output and therefore entirely bypassing the whole ADC stage ?
No need for a detailed reply, just a quick answer would be fine. I'm just trying to understand the basics.
It's all digital inside the FPGA. It's just a DDS that gets switched in place of the ADC input.
OK thanks for that.
Just to clarify, if the ADC was faulty, the internal signal generator would still give the correct levels ?
Yes. The ADC XO (separate part from ADC itself) has to be working. But otherwise bad outputs from the ADC itself shouldn't affect things when in sig gen mode.