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PNA-X IP3 performance, is my PNA-X faulty?

Question asked by CheeCheng on Jun 1, 2009
Latest reply on Jun 8, 2009 by CheeCheng

I am an user of PNA-X and lately I made an IP3 measurement. Some question for the PNA-X.

I ran from 200MHz to 3GHz at 100MHz spacing for TOI test. Every segment has different input power level. F1 and F2 separation = 1MHz. So, the Upper side band is 2MHz away, while the LSB is -1MHz away (reference to F1). IF BW = 50Hz.

First I do all the setting and cal properly. I set the receiver attenuation to 30dB.

After cal, I connect the input to output using thruline. I noticed that there is always a peak at the upper side band (2.102GHz) of F1=2.1GHz, F2= 2.101GHz while the lower side band (2.099GHz) is fine. 

This means that without connecting the DUT, the IP3 of the PNA-X (port 2 attenuator + receiver in particular) has already = (2xF1 – IM3) / 2 = {(2x-1.03} - (-63.763)} / 2 = 30.85dBm 

My DUT output IP3 > 35dBm. This only happened at 2.1GHz. Is there a specification of the IP3 for the receiver (or attenuator) at port 2? Is this PNA-X faulty? I cant measure my DUT esp at this particular frequency.

Screen captures below. Kindly note at the peak for the green trace. Is my particular PNA-X faulty? I increase and decrease the power level, the USB power levels do increase and decrease accordingly, while the calculated IP3 maintain low at around 30dBm.  (I thought there is a 2.1GHz WiFi in my office) ... 00-h/2.png ... 00-h/1.png

I have re-calibrated twice (btw, I noticed that one has to "preset" the qeuipment after finished power source and receiver cal before redo the calibration, else the power will be 3dB lower and cant pass the source cal?)

Help / advice urgently needed. Many thanks.

Chee Cheng