Matching unused port of FET microstrip oscillator, to 50 Ohm or to open-circuit?

[Terminator3]

Hello! What is optimal and safe way to do that?
Classical approach - LO output at the drain, match 50Ohms output line to Zl=-Zout near transistor.

I am going to take LO from gate resonator, so drain port remains unused. Should i match its -Zout to open-circuit, or make "fake" 50Ohm line with 50Ohm resistor and match it to this thing?

For example, if matching 50 Ohms, then go to -Zout=ZL=(70-j17.1) from 50 Ohm with two stubs. But i need that 50 Ohms, and it looks that power will be lost in that unused direction.

If match to open-circuit, the problem is open-circuit have R=1, Im=0 at the right part of smith chart outer circle. The only way to match it to -Zout=ZL=(70-j17.1) is to add resistor ~75Ohm and then a short microstrip.

Both cases have unwanted resistor to GND. In the papers i see photos of single open-circuited stub at drain, how they do that?

 

[biff44]

if u analyze the 3 terminal circuit, it will become obvious that you have to present the proper impedance at each terminal in order to satisfy the oscillation conditions. Those impedances is not necessarily resistive or 50 ohms.

 

[Terminator3]

I understand that. My oscillator ports are matched!!! Using book. Then i want to get rid of drain output line. For example, it is connected to some antenna,etc. and matched. So i cut it out. But drain port still must have -Zout=ZL=(70-j17.1). It was matched to 50Ohms. Then i cut 50 ohms out, what should i do, add 50Ohm load, or match to open circuit?

 

[BigBoss]

In oscillator design, first constraint is proper impedance that satisfy oscillation conditions.Second constrained is Output Level and Phase Noise
That's why you can not consider matching issue in oscillators as same as in amplifier design.You should do many Load Pull simulation to find the optimum Load Condition which satisfies all those things simultaneously.

 

[Terminator3]

Let me ask another way: what should i do with unused output port of working oscillator, that was matched to 50 Ohm. I think simplest thing is to add 50 Ohm load. Because it was matched in some way, that 50 Ohms transformed to some reflections outside stability circles, and so on. Then i thought about replacing 50 Ohm load with open-circuit, and change matching circuit on this port. So i can't understand is it technically possible.