Power conversion from mW to dBm?

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?

Answer 1

[Star Strider]

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.

[Randy Marsh]

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]

I have figured it out:

u=100; %mW
solution = 10*log10(u)+30

[Star Strider]

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]

So, is my code from the second post correct?

[Randy Marsh]

u=100; %mW
solution = 10*log10(u)+30

I don't know if 'u' here is in 'mW' or in 'W'.

[Star Strider]

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.