Help need in analog circuit design to get phase and amplitude of two signals.

[veerubiji]

Hi,
I am generating sine signal with 125 KHz using micro controller and giving it to Capacitive(cylindrical shape) sensor. If the sensor out is low to read then i am using two amplification stages to increase signal amplitude. I am using multiplexer to select best signal from sensor out.  The out signal also 125 KHz but there is a phase shift in the signal based on medium between electrodes.

Now I want to calculate phase shift between two signals(vg and vr) as well as both signal amplitude. I am confusing which circuit will gives max amplitude of both signals and phase shift between two signals?  I am able to read phase shift and amplitude of both signals using micro controller. I can use ADC to read amplitudes but i am worrying about phase shift.?

I am attaching simple block diagram of my circuit as shown below.

Any suggestions which circuit will gives phase shift as well as amplitude of input and output?