Specifications

Third Order Intermodulation Distortion Performance Test
Agilent Technologies
PSA Series Spectrum Analyzers
Test and Adjustment Software
Third Order Intermodulation Distortion Performance
Test
This test measures the Third-Order Intermodulation distortion produced by two discrete
signals, and computes the Third Order Intercept (TOI) point.
Two signals separated by 100 kHz are combined in a directional bridge or directional
coupler (for isolation) and are injected into the analyzer input. The spectrum analyzer
measures the amplitude of the lower and upper distortion products. TOI is computed using
the higher (worst case) of these two products.
Testing begins by turning on one signal source and measuring the signal level at the
directional bridge/coupler output port with a power meter. The bridge/coupler is then
connected to the analyzer input, and the signal from the source is displayed on the
analyzer. The second signal source is turned on and its amplitude is adjusted to match that
of the first source.
In the 3 Hz to 3 GHz band, a filter is used to attenuate the second harmonic of the signal
closest to the distortion product being measured. Above 3 GHz the analyzer provides
internal preselection so the source does not require an external filter.
Required Test Equipment
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