Making Measurements Using Spectrum Analyzer Mode
Third Order Intermodulation Measurement (TOI)
It is important to verify that the TO1 being measured is coming from the device under test and not from the spectrum analyzer. An easy way to do this is as follows:
1.Set up the TO1 measurement and turn it on.
2.Press lJKEEF], ATTEN AUTO MAN (AUTO) and increase the attenuation + 10 dB by pressing ($J
3.If the displayed result of the TO1 measurement remains constant, then the value is the result of the device under test.
4.If the displayed result of the TO1 measurement decreases, then the value is due to spectrum analyzer distortion and not the device under test. In this case, continue to increase the attenuator setting until the measurement result no longer changes as the attenuator is changed. When the value remains constant, the result is from the device under test.
Increasing the attenuator setting of the spectrum analyzer decreases the level of the signal internal to the spectrum analyzer and therefore decreases the distortion generated by the analyzer. Refer to the characteristics information in specifications and characteristics in your calibration guide for a graph of the typical distortion performance of the spectrum analyzer.