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I am using python to get data from BB60C, but I met some problems during unit conversion to mV from I/Q data .
In this reference https://relatedcontentdemo.kinsta.cloud/sigdownloads/SDK/online_docs/bb_api/index.html#IQDataTypes
It said dBm = 10log (I^2 + Q^2), I^2+Q^2 is P in mW, I tried AM_in_mV = (P_in_mW * 0.05)^0.5
But the result is not the same as in SPIKE. Where did I get wrong?Is the I/Q data 16-bit integer or are you using the 32-bit floating point data from the API? If you are using the 16-bit integer data, there is an additional scale factor you must account for.
Also, what value are you comparing it to in Spike? If you are looking at a modulated signal, you’re going to need to do a channel power measurement. If looking at a CW, then the instantaneous I/Q power will have more relevance.
dBm = 10*log10(i^2 + q^2) is the correct equation. Make sure it’s log10 not log2.
Look forward to your response.
I tired to convert I/Q data to AM in mV (AM linear)and want to compre it with SPIKE under zero span mode.
The iq data is returned by bb_get_IQ_unpacked(). I’m not sure it is 16-bit or 32-bit. I’ve tested.
bbConfigureIQDataType(handle,’bbDataType32fc’) bbConfigureIQDataType(handle,’bbDataType16sc’)
but the result looks the same.Jeremy,
To convert to mV (voltage) you have to use the V = sqrt(P*R) Ohms law relationship. The system is 50 Ohm. This simplifies to
mV = 10^((dBm+46.9897)/20)
You can also derive an equation to go directly from I/Q to mV without needing to log/power the data too.
Use the 32-bit floating point values to avoid the need for an additional scalar.
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