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watson822 New Member Offline Posts: 3 Taiwan	peak power calculation Dec 19^th, 2011, 4:57am please help me calculate peak power in 802.11g 6Mbps 26dBm output, thanks
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watson822 New Member Offline Posts: 3 Taiwan	Re: peak power calculation Reply #1 - Dec 20^th, 2011, 10:27pm sorry, is peak voltage, not peak power, anybody know how to calculate? please kindly help~~
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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: peak power calculation Reply #2 - Dec 21^st, 2011, 10:17am have you read the specification for the standard?
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aaron_do

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Re: peak power calculation
Reply #3 - Dec 21^st, 2011, 4:57pm

First of all, peak voltage depends on the impedance level. Usually there is some VSWR specification for the standard. For instance, the transceiver may need to work for a VSWR of 5:1, and not explode with a VSWR of 10:1. So for a 50-ohm system with a VSWR of 10:1, you are potentially looking at 500 ohms.

Power = V²/R

You should also take into account the peak-average power ratio. It depends on the modulation scheme. For a sine wave it is 3 dB. But I'm guessing that for 802.11g it's higher.

Lastly, the peak voltage that you are actually going to get in your circuit can be highly dependent on the implementation. It depends on things like the harmonic content of the signal, and also whether or not there are any transmission lines between the components.

Hope I haven't missed anything out, and feel free to correct me anywhere...

cheers,
Aaron

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there is no energy in matter other than that received from the environment - Nikola Tesla

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weber8722

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Posts: 95

Re: peak power calculation
Reply #4 - Jan 2^nd, 2012, 1:44am

All looks right. Here is a nice detailed article :):

http://www.elliottlabs.com/documents/OFDM.pdf

For peak-voltage calculation you also have to be aware of peak-to-average power ratio. For a pure sine wave the peak power averaged over one RF period is constant, but modern modulation schemes such as OFDM have some amplitude modulation.

Bye Stephan

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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: peak power calculation Reply #5 - Jan 2^nd, 2012, 12:46pm Sometimes ytou will find peak vs. average is a function of the modulation. So its usually a good idea to check the specification.
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