red-pitaya-analog-input-model

Red Pitaya analog input SPICE model (GNUcap/ngSPICE compatible)

DC coupling can become a problem when intending to use Red Pitaya for RF with non-DC-shorted antennas. Here is a model for the analog input filtering of the Red Pitaya for LV and HV positions.

• f > 100 kHz, HV has 30 dB less gain than LV.
• f < 1 kHz, HF has 21 dB less gain than LV.

Red Pitaya Analog Input transfer function

Of course, the best way to use Red Pitaya for a 50 ohm RF system is to replace the existing circuit with one appropriate for 50 ohms, as the Red Pitaya HamLab has done or as others have previously done.

Run Simulation

gnucap -b LV.net

Plot Simulation output

./PlotTransfer.py

References

• Red Pitaya Analog Input schematic
• measured Red Pitaya LV transfer function