check IQ performance - Githubissues

sinara-hw / Phaser

Quad channel 1GS/s RF generator card with dual IQ upconverter and dual 5MS/s ADC and FPGA in EEM form factor

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check IQ performance #114

Open hartytp opened 4 years ago

hartytp commented 4 years ago

verify that carrier nulling, sideband suppression etc are all roughly within spec

hartytp commented 3 years ago

Personally, I'm happy leaving the bigger FPGA since IIRC it doesn't make a huge difference to the overall cost, and gives us more space to experiment with different designs in the future. However, I'm happy to leave the final call to @jordens if he has stronger opinions.

gkasprow commented 3 years ago

shall I close it?

jordens commented 3 years ago

Leave the current one. The stft needs a bit more resources.

hartytp commented 3 years ago

oops, I posted in the wrong thread.

Re FPGA size: agreed, let's stick with the one we have.

Re checking IQ performance: let's leave this open until someone has checked it, but it shouldn't be a release blocker (right now there isn't a clear pass/fail specification for this anyway)

pathfinder49 commented 3 years ago

I've measured the uncompensated Carrier feedthrough (LO leakage) and sideband suppression with the LO at 2.875 GHz. The uncompensated sideband suppression was -38 dBc. The carrier feed-through was -37.5 dBm. Nominally, these are close to typical values. The regarding the carrier feed-through, I'd like to understand #130 before deciding whether this is to spec.

pathfinder49 commented 3 years ago

This performance is similar after addressing the LO output amplitude. Playing with the DAC QMC settings I saw siedband powers of -45 dBc. Adjusting the TRF ioff and qoff, I could reduce the LO loakage to -68 dBm.