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Circuit note CN-0248: Interfacing ADL5387 and ADL6510

Question asked by biancajs on Aug 13, 2014
Latest reply on Aug 14, 2014 by bsam

Hi there,


I have found the circuit note CN-0248 which shows a way of interfacing the ADL5387 evaluation board (I/Q demodulator) with the ADRF6510 evaluation board (Filters and VGAs for I/Q inputs). This looks to be an ideal set up for the application I have in mind, but I have a few questions regarding the set up of the boards in this way... (note that I wish to omit the ADL5336 board, and the input to me demodulator will be a beat signal from a photodetector)


1. I see no reason why I couldn't use the ADL5380 in place of the ADL5387 (as I need to demodulate higher frequency signals) - is this right?


2. I would like to demodulate my signals down to DC by removing the baluns on the ADL5380 eval board to give a differential output (but keeping the inputs single ended). If I also remove the input balloons on the ADRF6510, will I be able to pass this DC signal in?


3. I have noticed that in this differential configuration, the output impedance of the 5380 (or 4387) is 450 Ohm, while the input impedance to the 6510 is 400 Ohm. Is it OK to simply connect the two? And what are the consequences of this matching imbalance?


4. In the example given in the circuit note, the differential outputs from the 6510 board are passed into two AD8130-EBZ boards, which provide a differential to single-ended conversion before the signal is detected on a scope. I would also like to do this (convert the signal so that it can be sampled with a scope), but as my signal will be at DC, I'm unsure whether I can still use this part. Will it work at DC? And if not, is there a similar component which will?


Any help with the above, or notification of any faults in my proposed set up, would be really appreciated. Thanks