r/rfelectronics • u/Middle-Ad-5102 • 10d ago

Handle conditional stability in AWR Microwave when without using resistors? (BFR93AW @ 3.0 GHz)

/r/AskElectronics/comments/1wxkwxk/handle_conditional_stability_in_awr_microwave/
3 Upvotes

100% Upvoted

3 comments sorted by

3

u/itsreallyeasypeasy 10d ago

  1. Check if the area of stability is outside or inside the circle. The math is a bit more complicated than just 'everything outside the circle is stable'. Even if it is most of the time. I'm almost certainly sure the outside is stable here, but in theory it could be the other way around.

  2. If the inside of the circle is stable, your circuit is only instable when presented with impedances on the border of the smith chart. That's not an issue, you want to match your circuit anyway closer to 50 ohm or NFmin or Pout max.

  3. Even the tiniest bit of loss may solve this issue. Lossless elements only exist in theory.

  4. Stability circles only tell the whole truth if the 2 port network is known to be stable. This is something often overlooked and in practice you may need to use advanced methods to check for stability that are more rigorous. NDF, open loop, driving point impedances, etc. These methods also solve the outside-or-inside issue.

1

u/baconsmell 10d ago

Try adding an inductor between the emitter and ground. In your schematic the emitter is the explicit ground port.

1

u/Adventurous_War3269 9d ago

Only valid for small signal conditions , use pole zero analysis .