Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Impedance measurement using I/Q demodulation

Status
Not open for further replies.

Phataas

Newbie level 4
Joined
Feb 17, 2013
Messages
6
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,342
Hello!

I want to measure an unknown impedance using an I/Q demodulator.

Setup:

I was thinking of using a DDS (Direct Digital Synthesizer) as the sine wave signal generator. Splitting this signal to a reference signal and an excitation signal. The reference signal will go directly to the LO input while the excitation signal will go through a "black box" with an unknown impedance (RC, no L), and then to the RF input. The signal out from the "black box" will probably be attenuated and phase shifted. I am interested in getting the phase shift phi = arctan(Q/I) and amplitude A = sqrt(I^2 + Q^2).

The AD8333 has this block diagram:

**broken link removed**

The I and Q outputs are currents, so I would use a current-to-voltage converter to get this converted to a voltage. Assuming the voltage is alternating I would low pass filter the alternating voltage at each output (I and Q) and sample this value for a time (100ms) with an ADC and calculate the average on my micro controller. I am targeting measurements in the close to 0 to 300 000Hz intervall.

Does it sounds like the AD8333 will fit my needs?
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top