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Phase detection using passive or active mixer

Dear community,

I wish to make a phase detection of two sinus signals. I am a beginner in the field and seeking for some advices.

My setup would be the following:

- DDS (i think of using the AD5932) to deliver my reference signal. I want to have a frequency range variable but the limit of the AD8343 is already enough for my application,

- This signal goes thought my DUT. Since this one is tied to the ground, I am measuring the current flowing thought a reference and transposing it into voltage using the AD8220 instrumentation amplifier

I want to make a phase detection on the signal delivered by the DDS and the one measured at my DUT. I thought of using a mixer for it (the AD8343 or the LT5526) 

I thought of feeding my reference signal to the RF input and the received signal from the DUT to the LO input. But i read that i should be careful to the reflexion of the LO signal on the RF and the output. So this would be my first question which filtering should i use to avoid this effect?

the output signal will finally be feed to an ADC and processed with a Micro controller to extract the phase and amplitude change. 

My second question more theoretical probably, but what is the difference between a Passive mixer and an active one? Does it make a difference for sinusoidal signals? 

I thank you in advance for your help and your advices :)

Best regards,