Power handling in RF waveguide components

[alfio1234]

Hello everybody,

I try to study the power handling of RF waveguide components, i begin with a standard waveguide WR112 at 8.4GHz, i calculate the power breakdown using the formula in Pozar's book

Where Ed is the breakdown voltage of air that fills the waveguide and equal to 3*10^6 V/m.

I find using this formula that for a WR112 at f = 8.4 GHz the Pmax is 1.65MW, and if i put this value of power in the source window in HFSS, then in the plot of E field i find exactly 3*10^6 V/m as the maximum value.

But there is a problem, when i use the Multipactor Setup in HFSS on the same waveguide and frequency, the setup solution is that the breakdown power is around 15 kW, someone can help me?

Sorry for my bad english

 

[Kobba]

Hello,

The error involves confusing two different power breakdown methods: 1. is a corona breakdown where the air is ionized and 2. a multipactor breakdown that happens in a vacuum. A multipaction event can only happen in a vacuum except for some small seed electrons.

 

[alfio1234]

Yes, i study after posting the question, and i understand the difference between the two case, so how can i define the power that causes arcing in waveguide filled with dry air?

 

[Kobba]

Electrical breakdown of air can happen when the electric field is strong enough; about 3e6 V/m. If your air-filled waveguide has sufficient power to generate an electric field strong enough to break down air then you will get a corona event.