ADRF6520's input common mode voltage is 1.375V, while output common mode is 1.65V. There is no on-chip mechanism to change these common-mode voltages, so you must match the pre- and proceeding stages to the ADRF6520's common-mode.
The LTC5594's IF Amps' output common-mode voltage is 0.9V by default, but can be change from 0.5V to 2.0V via the Vcm pin. I'd drive Vcm = 1.375V to match that of the ADRF6520.
You might have to implement a level shifter between the output of the ADRF6520 and the input of the AD9684, to shift from the 1.65V to 2.05V on the AD9684's input.
Is DC coupling a must for your application? With the larger signal BW's in the Receive chain, it is often unnecessary to DC couple given one uses large enough AC coupling caps.
In addition to setting LTC5594's Vcm pin to 1.375V, you also need to properly set the output ground return resistors, R3-R8. The LTC5594 has current-mode IF outputs that require a termination resistance to create output common-mode voltage. The optimum current is around 18mA per output pin. The internal feedback adjusts the current to match the output common-mode voltage to what is set on Vcm.
Thank you for your help but I already know everything written in datasheets. I need an implemented demonstration applicable for Zero IF. As written on the top of my image shared, it is a Zero-IF application, so DC coupling is a must.
Please send me a level shifter for that apllication specific case.