Battery capacity and Power Amplifier Efficiency

[dolgaleb]

I am working on a transmitter chain that must output 10W for 0.1 hrs and remain OFF during 0.8hrs. The signal is a square wave with 1% duty cycle. The source is a 12V 6000mAh battery with C rating of 2.

This transmitter must run for 12 hrs with the characteristics described above. Then it must run another 36 hrs in CW mode at 50 mA.

I have to prove that the battery can supply the required power in the period of 48 hours with some margin.

In addition, I have to determine what the efficiency of the Power Amplifier described in the attached file needs to be to pass the test.

I am not familiar with this type of analysis and would like to get some guidance regarding the math and/or direction to a technical source that may explain the methodology in detail. Let me know if you have any questions.

 

[BigBoss]

Amplifier Efficiency depends on itself, not working duration.
It's simply how much power drains from the power supply and how much power delivers to the load.
Working with pulsed mode or CW mode has to be separately examined and efficiency is generally not simulated in pulsed mode but measured.

 

[mtwieg]

So some simple math:
12V*6000mAhr = 72Whr.
Your description of the signal is a bit confusing. You say it operates 0.1hr on then 0.8hr off, which is a duty cycle of 11.1%. But then you say "The signal is a square wave with 1% duty cycle". Not clear if this is an RF signal (and you're describing amplitude modulation) or not.
Anyway if we use the 11.1% duty cycle then the average output power is 10*0.1/(0.1+0.8) = 1.11W.

So in theory the battery could support this mode of operation for 64.8hr, with perfect power efficiency. To operate like that for 12 hours would require an overall power efficiency of at least 18.5%.