Impedance Analyzer design using the AD8302

[ddsRV]

Hi there,

I’m using an AD8302 gain/phase detector in a simple divider setup to measure a quartz crystal. Right now I can log the raw VMAG and VPHS voltages vs frequency.

What I’d like to end up with are analyzer-style plots such as:

|Z|(f) (impedance magnitude vs frequency)

G/B admittance curves (conductance & susceptance vs frequency)

Basically, I want my sweeps (image 1) to look more like what you’d see on a Keysight 4294A(image 3) or in QCM literature(Image 2).

Question: What’s the right formula pipeline to take VMAG/VPHS → impedance/admittance curves? Do I need to convert to a complex ratio first, or is there a simpler direct way?

[Terry Bites]

1 Buy a nano VNA and stop worrying. I'm still in the warm fuzzy stage of this new romance.
2 Read up on how a VNA works.
3 https://hamprojects.wordpress.com/2016/02/21/hf-arduino-vna-english-version/
4 https://hackaday.com/tag/ad8302 Yep, buy a nano........