Power conversion from mW to dBm?

2017 4 25
1 个回答
更新时间：2017 4 26
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Determine the power of a signal in dBm if absolute value is 100mW. Code:
u=100mW;
10*log10(u)+30
Reference: https://www.mathworks.com/help/dsp/ref/dbconversion.html
Could someone show the correct code for this conversion?

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回答（1 个）

Star Strider
Star Strider 2017-4-25
编辑：Star Strider 2017-4-25

0 个投票

That seems to be correct according to the Wikipedia article on dBm.
An anonymous function version is:
dBm = @(mW) 10*log10(mW); % dBm As A Function Of Power In milliWatts
EDIT — Corrected units.

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Randy Marsh
Randy Marsh 2017-4-25
Could you show an actual working code for finding the power of a signal in dBm if absolute value is 100mW?
If not, where can I find code sample for this conversion?
Randy Marsh
Randy Marsh 2017-4-25
编辑：Randy Marsh 2017-4-25
I have figured it out:
u=100; %mW
solution = 10*log10(u)+30
Star Strider
Star Strider 2017-4-25
The inverse is also given in the Wikipedia article, although it wouldn’t be difficult to calculate:
dBm = @(mW) 10*log10(mW); % dBm As A Function Of Power In milliWatts
mW = @(dBm) 10.^(dBm/10); % mW As A Function Of dBm
NOTE — According to the Wikipedia article, the units in my original Answer were in Watts, not mW, an error on my part in transcribing the wrong equation. I corrected it, and in this Comment. The units are now correct.
For units in Watts:
dBm = @(W) 30 + 10*log10(W); % dBm As A Function Of Power In Watts
W = @(dBm) 10.^((dBm-30)/10); % W As A Function Of Power In dBm
Randy Marsh
Randy Marsh 2017-4-26
So, is my code from the second post correct?
Randy Marsh
Randy Marsh 2017-4-26
u=100; %mW
solution = 10*log10(u)+30
I don't know if 'u' here is in 'mW' or in 'W'.
Star Strider
Star Strider 2017-4-26
Here ‘u’ is in W, according to the Wikipedia article.
My apologies for the delay — serious computer problems. Firefox no longer works on my Win 8.1 machine, and routinely crashes it, destroying my MATLAB configuration files as well.

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