RFmx Bluetooth Auto Level Setting Cannot Detect Signal Power Level in In-band ACP Measurement

Issue Details

I am using InstrumentStudio with the RFmx Bluetooth Soft Front Panel (SFP) to run an in-band Adjacent Channel Power (ACP) measurement with a signal coming from my Device Under Test (DUT). Given the way my DUT behaves, I configure my measurement's reference level with the auto level setting. However, the measurement ends up setting the reference level to power values way below the ones coming from my DUT. Why is this?

Solution

RFmx for Bluetooth® Test is measurement personality that extends the capability of NI RF instrumentation for classic Bluetooth as well as Bluetooth Low Energy (LE) signal generation and analysis. 

When dealing with an ACP measurement within RFmx Bluetooth, the Channel Offset Mode setting of the measurement will affect the auto level algorithm. When this setting is configured for In-band measurements, the auto level algorithm won't be able to properly calculate the reference level of a Bluetooth input signal. The key step to overcome this behavior is to run the auto-level algorithm for the transmit channel and then move to In-band configuration. The exact steps to be followed in the RFmx Bluetooth SFP are:

1. Open an RFmx Bluetooth session for an ACP measurement.
2. Keep the Channel Offset Mode setting at its default value, Symmetric Mode.
3. Move to your Bluetooth signal Channel 0's frequency (2.402 GHz) and run the auto-level algorithm.
4. Change the center frequency to Channel 39 (2.441 GHz).
5. Change the Channel Offset Mode to In-Band.
6. Run the ACP measurement.
7. Repeat steps 2-6 for all the other channels of interest.

Additional Information

Using an incorrect reference level for your measurement can have multiple unwanted side effects. You could saturate the Analog-to-Digital Converters (ADC) of the instrument and affect the accuracy of your data. You can also affect any I/Q Power Edge Trigger configured for your measurement. It is paramount that you ensure the reference level used in your measurement is appropriate based on your input signal's power.