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Modeling input/output impedance of the ADL5350.

Question asked by bmackenzie on Mar 7, 2012
Latest reply on Mar 29, 2012 by Rui

Hello,

 

I am wondering what the best way to model the input and output impedance (terminating impedance) of the ADL5350 is?

 

Naturally, the terminating impedance the signal path leading in to and out of the mixer are known. However, I'm a little confused on how to represent the mixer given that the ADL5350 operates by varying the drain-to-source channel conductance of a FET junction connected from the RF/IF node to ground. Would this junction have any impact on the impedance of either of the two sides, thus affecting the match, as the LO port is driven? Or is it really as simple as the "simplified schematic" (Figure 57) of the device on page 17 of the datasheet depicts?

 

Can I conclude that if the input (RF Port) and output (IF Port) are matched to the same impedance, regardless of what that impedance is, that the mixer's and it's simplified "variable resistance to ground" at the RF/IF node has relatively no impact on the match?

 

I'm using the ADL5350 in a typical down conversion setup at around 130MHz.

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