B
billcalley
- Jan 1, 1970
- 0
Hi Guys,
From what I have been able to absorb now from all of your really
terrific responses is that it is totally and completely impossible to
LC match, even theoretically, a purposefully mis-matched active
device*, and then look back into that mis-matched network and see a
perfect 50 ohms. However, the purposefully mis-matched active device
WILL get to see the impedance it wants to see. And all this is due to
the reciprocal nature of LC matching networks. Thus, it would be
wise, as you have all mentioned, to design any non-50 ohm LNA or PA to
be as close to 50 ohms as possible, or to design the next connecting
stage so that it properly works with something other than 50 ohms --
'cause there is no way to "fix" this mis-match issue with a LC
matching network. Is that correct, or have I misunderstood
something? (I can't believe I didn't know -- or didn't understand --
this stuff from the get-go! A major glitch in my knowledge-base,
that's for sure.)
Many Thanks,
-Bill
*The mis-match created so as to optimize an LNA transistor's input for
NF, or a PA transistor's output for P1dB, to name two common reasons.
(HAD TO OPEN-UP A NEW THREAD BECAUSE GOOGLE GROUPS APPARENTLY REFUSED
TO POST THIS, EVEN AFTER TWO TRIES -- OR AT LEAST IT DID NOT SHOW UP)
From what I have been able to absorb now from all of your really
terrific responses is that it is totally and completely impossible to
LC match, even theoretically, a purposefully mis-matched active
device*, and then look back into that mis-matched network and see a
perfect 50 ohms. However, the purposefully mis-matched active device
WILL get to see the impedance it wants to see. And all this is due to
the reciprocal nature of LC matching networks. Thus, it would be
wise, as you have all mentioned, to design any non-50 ohm LNA or PA to
be as close to 50 ohms as possible, or to design the next connecting
stage so that it properly works with something other than 50 ohms --
'cause there is no way to "fix" this mis-match issue with a LC
matching network. Is that correct, or have I misunderstood
something? (I can't believe I didn't know -- or didn't understand --
this stuff from the get-go! A major glitch in my knowledge-base,
that's for sure.)
Many Thanks,
-Bill
*The mis-match created so as to optimize an LNA transistor's input for
NF, or a PA transistor's output for P1dB, to name two common reasons.
(HAD TO OPEN-UP A NEW THREAD BECAUSE GOOGLE GROUPS APPARENTLY REFUSED
TO POST THIS, EVEN AFTER TWO TRIES -- OR AT LEAST IT DID NOT SHOW UP)