I plan to use ADRF6820 as the de-modulator for a zero-IF recevier.I use the ADRF6702 as the modulator to generate the RF signal to test ADRF6820.The sheme is shown as below:
As you see,I used a oscilloscope which is connected to the BBIP and BBIQ of the ADRF6820 eval board.Here is the waveform of the I channel
As I am not sure if the output of the ADRF6820 is correct.I removed the 100nF capacitors of the output circut of Q channel,Just like below,
Here is the waveform of Q channel after removing the 100nF capacitors(figure 1).And I noticed that there may be a relatively high amplitude DC component,I placed a capacitor between the output of the ADRF6820 eval board and the oscilloscope to filter the DC component.(figure 2)
figure 1 figure 2
As this is my first time to design a zero-IF system.I want to know what the waveform of the baseband output should be like?Can you give me some suggestion about how to design the baseband output circut of ADRF6820 for zero-IF receiver?
Thank you all
1) Keep the DC blocking capacitor as it is and observe the output in the default customer evaluation board settings (diff to single-ended through balun)
2) What is your RF frequency of operation? Can you check the output of ADRF6702? Do the waveforms look as expected? If the RF frequency is too high for you to observe with the scope, you might try changing the RF frequency to a lower one for now.
3) Do you have a signal generator that has an arbitrary waveform generation capability?