TWT efficiency and RF off power consumption

[satellite]

twt efficiency

Dear friends,

in estimating the power consumption of an RF system including a TWT
I am using a graph showing efficiency wrt OBO (Output back off), and I know tube saturated power.
Nevertheless when no RF is fed in the TWT i don't know what is the
consumption of the TWT. Is there any mean to evaluate it from OBO-efficiency curve!
Any suggestion? Any useful material on the subject?

Many thanks,

Satellite

 

[Borber]

twta efficiency vs output back off

TWT operates in A class. Power consumption does not change with input RF power.

 

[Catallo]

twta obo efficiency

Life is not so easy!

TWTs have a consumption that is increasing with output power or backoff.
At zero input RF consumption is 1/3 or 1/4 wrt saturated power consumption.

More like class AB amplifiers!

 

[RRRAO]

reasons why twta output saturates

Power consumption = input power - power recovered by the collector
or
power consumption = power disspated in the collector+filament power +power disspated in the slow-wave structure+RF loss in the structure.

 

[Lupin]

Hi satellite,

in which band are you working? Do you have only one carrier or multicarriers? It should reduce your efficiency..

Let me know.

Regards,

Lupin