We set the transmission bandwidth of AD9364 to the maximum, that is, RF BW = 40m, and then the baseband signal is a spread spectrum code with variable carrier frequency.
When the carrier frequency is 0, the RF signal quality observed by the spectrometer is very good, as shown in the figure below.
However, when the carrier frequency is 1.625M, the RF signal observed by the spectrometer seems to be the superposition effect of two peaks, as shown in the figure below.
In theory, when the carrier frequency of baseband spread spectrum signal is 1.625M, the RF spectrum should shift to the right compared the one when carrier frequency is 0, but the signal quality is poor.
We don't know why and how to solve this problem. I hope to get your valuable advice, thank you very much!
Have you checked with the CW signal? Please check with and without offset whether you are seeing any difference or any additional spur is seen.
Please make sure that you are running all the necessary calibrations.
We read back the calibration status indicator to show that all calibrations have been completed.
Also we transmit a single carrier signal, and the RF signal observed by the spectrometer meets the requirements (image suppression, local oscillator suppression).
By the way，have you used 9364bist mode to transmit PRBS internally? Is PRBS data rate the set transmit data port rate?
Thank you very much for your reply
Please refer to the below link for more details on the BIST.
smiey said:In theory, when the carrier frequency of baseband spread spectrum signal is 1.625M, the RF spectrum should shift to the right compared the one when carrier frequency is 0, but the signal quality is poor.
As an experiment, you can try to disable all the calibration running and see whether it improves the signal spectrum quality.