I am taking an output impedance measurement using the 3-port (voltage / current) method. Here is my calibration test setup:
I feel this is a very good test setup, and these are the shortest cables I can readily locate. Everything has the look and feel of "good working order" or is brand new. I used the J2102B as I assumed I would have low output impedance and in Steve Sandlers text, "Power Integrity", page 142 he discusses using the J2102B in this location for low impedance measurements. Here are the 1 ohm calibration results.
Despite my best efforts I cannot remove the noise at the higher frequencies. I would like to verify that this is an expected result, or if something is incorrect in the test setup.
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I see. send me the complete setup. If you are powering the 1 Ohm resistor from the Line Injector, and you have 25mA flowing through the J2111A you would be measuring the output impedance of the Line Injector, which would still be an issue.
Top best guesses are:
1) You don't have the minimum 1.2V at the J2111A pins.
2) Noisy probe on CH2
I can try to replicate your measurement once I know all of the connections and that you have a minimum of 1.2V at the J2111A.
The high PSRR module is powering the Current Injector, I just did not include that in the diagram. The bias switch was set to positive bias. I'll send you a picture of the setup over email.
I don't see a power supply in your setup picture. The J2111A is a modulated current sink and therefore must have a power supply to sink from, and with a voltage greater than about 1.5V at the J2111A. The Bias switch also must be set to positive (for a positive power supply). This adds 25mA of DC Bias to put the injector into class A operation. You can use your own external DC offset if you want lower bias current, but then you also have to reduce the AC modulation level so that you actually get a sine wave modulation signal without clipping.
If you do already have a power supply connected, I would suspect your leads are long or you are using a noisy probe on CH2.
We do sometimes run a giveaway for a J2111A calibrator PCB that you can populate to make this calibration simpler. We don't sell it, but I made it for myself.