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ADRF6820 for zero-IF receiver

Question asked by Hansberger on Mar 3, 2017
Latest reply on Mar 8, 2017 by gyaliniz

Hello all,

     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

     

      Hansberger

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