Third Order Intermodulation Distortion (TOI) Performance Test

(M9393A)

This test measures the Third-Order Intermodulation distortion produced by two discrete signals and computes the Third Order Intercept (TOI) point. The intercept point is calculated and compared to the specification. The PXIe signal analyzer is specified with the conversion path set to Auto, and 40 MHz IF Filter path. The TOI is the theoretical power level where two input signals and their third-order distortion products reach the same power level. It’s impractical to measure the intercept directly because the signal analyzer would be in severe compression. The intercept is calculated from low level measurements from the following equation:

Where:

Where:

For this test, two signals separated by 100 kHz are combined in a power divider (for isolation) and injected into the analyzer input. The PXIe signal analyzer measures the amplitude of the lower and upper third-order distortion products. Worst-case TOI is computed by using the larger of these two distortion products.

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Required Test Equipment

Test Equipment1

Recommended Models2

Signal generator
(2 required)

PSG models
(see equipment list)

Power meter

N1914A3

Power splitter

11667C

Power divider

87302C

High power microwave power sensor

N8487A

Low power microwave power sensor
(for preamp options only)

8487D

30 dB attenuator
(for preamp options only)

11708A

Adapter, 3.5 mm (m) to 3.5 mm (m)4

83059A

Frequency reference module

M9300A
  1. Refer to the main required equipment list for a list of available adapters and cables determined by the source ETE configuration.
  2. Refer to the main required equipment list for alternative models.
  3. N1914A power meters with serial number prior to MY53040007 require Service Note N1914A-07 which fixes a power supply ground loop. The ground loop injects noise into the measurement circuits which can cause unstable measurements at low (-30 dBm) power levels.
  4. The 3.5 mm (m) to 3.5 mm (m) adapter between the power splitter and the DUT is critical in this test. Proper connector care and torqueing practices must be followed in order to insure optimal performance.

Connections and Setup Procedures

Click on the links below to view setup images.

ClosedSetup for Preamp Off

 

ClosedSetup for Preamp On