On 8/15/21 11:17 AM, David Eckhardt wrote:
I was addressing the INPUT as the requester! Why would I feed an RF
source to the output???????????
As noted, the OP was looking at inputs, but someone else suggested a way to measure outputs. My comment was on that.
Why would you want to feed an RF source to an output? Because you wanted to measure the S22? (or perhaps the S12 as well). And you want to do that while the amplifier is amplifying another signal. This is a common question in phased arrays where the amplifiers don't have isolators on the output.? A HF over the horizon radar is a good example. Lots of mutual coupling among the antennas, each amplifier is fed with a different waveform for things like beam steering, and the waveform isn't a sinusoid, but is modulated so pulse compression can be used.
This isn't easy <grin>
Hams have historically not tended not to be interested in this, because the regulatory environment encourages "single amplifier at which we can measure the power output", and it's also complex to implement.? But, particularly in microwave area, it's exceedingly common - MIMO and all that.? For all we know, the clever design of the Starlink transceiver uses it.
