Clarification regarding calculating input power of Power Amplifier

[pusparaga]

I want to find out input power for desired output power of a Power Amplifier. Below, I have attached formula for finding out input power. I have got confused with this formula. In the formula they are saying input power = (output power required - gain as mentioned in the data sheet) + 3 dB. I want to find out 38 Watts output power at 3.50 GHz. Gain is around 15 dB at 3.50 GHz. What should be the input power. I get confused how to find out input power using this formula. Clarify this issue.

 

[volker@muehlhaus]

15 dB - 3dB = 12dB
12dB power gain is factor 10^(12/10) = 15.8
38W / 15.8 = 2.4 W

 

[pusparaga]

15 dB - 3dB = 12dB
12dB power gain is factor 10^(12/10) = 15.8
38W / 15.8 = 2.4 W

Pin(dBm) = 38 Watts- 15 dB + 3 dB
Pin(dBm) +15 dB - 3 dB = 38 Watts
Pin(dBm) + 12 dB = 38 Watts
My doubt is how it becomes 38W/ 15.8. dB cannot be converted to dBm. It can be converted dBm
into Watts easily.
Don't mind. Clarify it

 

[volker@muehlhaus]

Clarify it

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