I use PNA N5221A. I am trying to measure S11 and S21 of of an antenna with an active matching network which needs a dc power suplly (5V, 20mA). At port 2 i use another antenna. Because of the non-linearities introduced by the transistor of the active matching network, i need low power level to verify small signal s-parameters simulation. So when i am trying to set the power level to a value smaller than-16 dbm i receive this error message:'Unleveled source 1, out 1'. I use two port standard SOLT calibration from 100 MHz to 1 GHz. What would possibly cause such an error? How accuracy is affected if i ignore the error message?
> I use PNA N5221A. I am trying to measure S11 and S21 of of an antenna with an active matching network which needs a dc power suplly (5V, 20mA). At port 2 i use another antenna. Because of the non-linearities introduced by the transistor of the active matching network, i need low power level to verify small signal s-parameters simulation. So when i am trying to set the power level to a value smaller than-16 dbm i receive this error message:'Unleveled source 1, out 1'. I use two port standard SOLT calibration from 100 MHz to 1 GHz. What would possibly cause such an error? How accuracy is affected if i ignore the error message?
Hi,
I have never used an N5221A - it is well outside my budget! Neither do I work for Keysight. But perhaps the following will be some help though.
1) You should state what options your instrument has, and firmware version too.
If you have a configurable test set (whatever option(s) that might be), it may allow you insert some attenuators in appropriate places to keep your signal level low enough for your DUT, but while at the same time allowing a measurement. Someone from Keysight will be able to give you more advice, but they are going to need to know more than just what model you have.
2) As for the 'Unleveled source 1, out 1" warning, the manual should tell you what it means. But even without looking at the manual, I can take a reasonable *guess* at what it is meaning. But my guess may be wrong.
Many signal sources, not just VNAs, have a range of powers and frequencies which they are specified to work over, then another range where they might work, but it is not guaranteed. If you set a level below -16 dBm, and the instrument tells you it is unleveled, then that power is not guaranteed. There's probably some AGC loop, and you are outside its design range. If you set the power to -16.1 dBm, the chances are it would be pretty close. If you set it at -30 dBm, I doubt it will be very close at all. But all guarantees are off.
The most obvious problem with ignoring such a message is that if -16 dBm is too high for your DUT, then you might get -16 dBm, even though you have requested something else.
An obvious question is what power do you want to put into the DUT? Given its an active antenna, I'm guessing you want to have an input far below -16 dBm. In which case, I suspect you really can't ignore that warnings, and need to address the situation.
Adding a 10 dB attenuator on the output will reduce your signal by 10 dB of course, but I suspect even -26 dBm will be too much for you.
I suspect if your VNA has the right options, or you can purchase the options, you can get around this, but I'm sure someone from Keysight can give you good advice once they know a bit more about your VNA, and what signal levels you actually want to put into the DUT.
Dave