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