Hi everyone,
The output signal of the companion board seems to be dirty with many spikes (see photo). I am using channel D. A 50 Ohm load is connected to the input (CHDI) and the output (CHDO) is connected to a spectrum analyzer. Here you see the entire span of the 2 GHz of IF. I have tried different LOs. They change the spikes but they don’t go away. The board is in downconversion mode with LNA+Mixer+PA enabled and the LO is fed to channel D. Is this normal?
The board is powered by external 5 volt. Using or not using external 10 MHz reference makes no difference.
Hi,
We checked several of our boards and obtained better results. Please find attached the spectrum analyzer screenshot.
Your results could be explained by several factors:
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Various external signals may have been picked up by the board (in his experiment the board acts like antenna) and that is seen on spectrum analyzer.
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If DC power supply is not sufficiently clean, it could be the source of these spikes.
Regards
Branko
Thank you. Just to confirm this is the latest board with the extra resistor (for the 10 MHz reference) removed?
Also are you distributing LO to the channel you are measuring with the LNA and PA active? Because when I disable the PA it becomes much cleaner (I think spikes mostly go under the noise floor).
Hi aabedii,
We used the latest 3v2 board with R80 removed.
We also replicated your test setup exactly as described: LNA, Mixer, and PA enabled, with all other settings matching your test conditions.
As you can see, the spectrum analyzer was configured with the same center frequency, span, and resolution bandwidth (RBW) as in your measurements.
Regards
Branko
