DIY Power Amplifier load tuning

Hi all,


I have a PA design where I need to do some load optimization. A manual load-pull may be an option, but I expect it might be pricey.

I was wondering if anybody has any good DIY options. I was thinking to follow the PA with a hybrid coupler and a variable load at the main output port (port 2 normally). I can then sense the forward power signal at port 4. The variable load could be just a parallel RC or RL.

Anybody have better ideas?


thanks,
Aaron

A 3 dB hybrid splitter will normally lose 3.5dB but <1dB when 1 port is unloaded such as with a high impedance diode cap forward or reverse power detector. Return loss performance is adjust if loaded correctly.

But then you can use it as a directional coupler to measure effects of variable load on return loss. A 75 Ohm hybrid can be modified to 50 Ohm by changing the balance 2xR inside the splitter.