RF output power vs. Frequency 1

[zjxie]

I have a theritical question about the output power vs. frequency. If I have a device which can deliver 100W at 1GHz with optimized matching for output power. Then I want to see how much power it can deliver at 2GHz with re-adjust matching. Does it exist a physical limitation on how much power will be degrade at higher frequency.

Appreciate for any kindly input.

 

[TWW]

Pmax is typically proportional to the inverse of 1/freq, or 1/freq^2 depending on the device. Threrefor you could expect 25-50W of optimized power.

 

[TWW]

BTW. 1/f is electronically limited, 1/f^2 is thermally limited.

 

[zjxie]

Thanks TWW,
What's the physics behind the electrical limitation and thermal limitation?
Does it due to the lower output impedance in higher frequency? Why the thermal become worse in higher frequency? Is the drain efficiency worse?

 

[TWW]

My humble attempt to answer these deep questions.

Question 1:

Electrical Limitation: Fundemental material parameters effects such as saturated drift velocity, mobility, gate length or base thickness, various resistive and reactive parasitic elements.

Thermal Limitation: Junction temperature rise, device area, thermal resistance.

Question 2: The lower impedance is part of the problem, the other part of the nasty equation is the rising reactance.

Question 3: Large Signal Drain efficiency will most likely be worse, whereas the small signal value may not change much.

Gota Go