Devlog 6

Got a ton of work done in a single session today.

Finished the local oscillator(LO) for the intermediary mixer, synthesizer, LO for the IF mixer, routed I and Q differentials to the ADC, wired up the ADC, added the debug sma port for the filters, added the 50ohm test line to the edge of the board.

Stuff that changed

I discovered that the + and − connections for the Q differential pair were opposite to what the ADC expects. After thoroughly reviewing the ADC datasheet, I decided that I can intentionally swap the differential inputs. This will invert the polarity of the Q component, which I plan to correct in the FPGA by negating the Q samples.

What is left

All that is left is for me to create the usb-C circuit as well as set up the ldos for the different power rails. As well as add the remaining test points and the debug LED. I also need to connect the pin headers for the stm nucleo controller board.

Thoughts

Debating on how I should connect the fpga dev board. I know that the frequency on the spi clock will be running at 105mhz (rise time is 4ns) as per the ADC’s datasheet. That is pretty high I feel for standard arduino jumper wires so I chose to solder wires however this still scares me a little. I am unsure of soldering the fpga’s header pins directly to the board either because of how difficult it will be to remove it afterwards. If anyone has any suggestions or ideas I would be really thankfull. Thank you.