Hi everyone!
I’m an electronics engineering student working on my first RF project for a future SatNOGS station. Still a work in progress, so nothing is completely closed or finished yet, but since this is my first time designing an RF Front-End, I’d really appreciate some feedback from the community before I send it to fab, especially with the PCB layout since I’m sure there will be a lot of room for improvement.
Context: Just ~4.3 km from a 240 kW EIRP FM tower (raw FM power at my antenna is around -1.3 dBm in worst-case). I used an input notch filter to keep the LNA operating in its linear region to avoid compression and IMD.
My approach:
- Input Filter: 5th-order Cauer notch [88–108 MHz] (1.09 dB IL @ 137 MHz).
- LNA: Mini-Circuits PGA-103+ E-PHEMT
- Stability (10 MHz – 4 GHz): R+L shunt to ensure K > 1
- Output Filter: 3rd-order Butterworth bandpass (2.5 dB IL @ 137 MHz, compensated with Friis)
- Used High Q High SRF components and 2% tolerances for the Cauer.
Simulated performance: ~22 dB cascaded gain, ~1.84 dB NF.
Simulated (QUCS-S, using .s2p models) and routed
(CPWG 50 Ω). Not built or bench-tested yet so I know results will vary. I’ll try to get my hands on a VNA to measure it soon.
Plots
Schematics
PCB
All files (full report, schematic, KiCad & sims) are open-source on GitHub if you want a deeper look, sharing it here in case it’s useful to anyone else dealing with strong local FM at these frequencies. github repo with all the files
Thanks for reading, feedback is really appreciated!
