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Satellite Communications/3dB backoff if using GaN BUC for single carrier

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Question
QUESTION: Sir,

Assume I am using a Ku-band GaN BUC's with Plinear spec as 80W (PSAT is 200W), if I transmit a Single carrier, the maximum power it can use is only 80W ?

If I transmit TWO carriers, I have to set 3dB backoff (from the Plinear 80W), so the total maximum power can only be 40W ?

Thanks,

Feng

ANSWER: Hi Mr Feng,
If you transmit TWO carriers the maximum power you can use is 40 W per carrier is the correct statement.
Cheers/GTRao

---------- FOLLOW-UP ----------

QUESTION: Thank you Sir. Sorry for a further question:
From the practical point of view, what are the differences between Plinear of GaN BUC and P1dB of GaAs BUC ?

I used to think, in the case of GaAs BUC, when it transmits 2 carriers we need to set 3dB backoff from P1dB.

Same situation for GaN BUC, to support 2 carriers we also need to have 3dB backoff from its Plinear ?

Feng

Answer
Hi Mr Feng,
Both definitions mean the same thing. Only difference is that the slope of the characteristic curve is to be considered. Liner parameter assumes that the slope is uniform from peak response to-3dB level and P1 dB defines it is not liner but is following different slope. So if you compare the response curves you will find that the minus 3dB points will be different with respect to frequency. In either case Back off is to be -3 dB which indicates bandwidth of the carrier occupancy in either case.
Cheers/GTRao

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TIRUMALA RAO G

Expertise

Satellite Communications Applications, Link Calculations, Teleports, Earth Stations,VSAT, Tracking, Mobile Communications, Next Generation Networks.

Experience

40 Years. Indian Space Research Organisation, PANAMSAT, Satellite Based VSAT Networks, IP Networks.

Organizations
ISRO, PANAMSAT, Engineering Institution for Higher Education (GVP College of Engineering), Consultancy.

Education/Credentials
Graduate in Electronics and Communication Engineering with Distinction. Guiding scholars for their Doctoral thesis in related areas in Academics.

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