Third Order Intermodulation Distortion (TOI) Performance Test

(M9391A)

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 directional bridge (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.

Click here for troubleshooting help.

Required Test Equipment

Test Equipment1

Recommended Models2

Signal generator3

M9381A Opt 1EA

Power meter

N1914A4

Power sensor

E9304A Opt H20

Power splitter

11667B

Directional bridge

86205A

50 MHz Low Pass Filter

RLC L3230

1.0 GHz Low Pass Filter

RLC F-30-1000-RF

2.0 GHz Low Pass Filter

RLC F-30-2000-RF

3.0 GHz Low Pass Filter

RLC F-30-3000-RF

6.0 GHz Low Pass Filter

RLC F-30-6000-RF

Adapter, 3.5 mm (m) to 3.5 mm (m)5

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. Two signal generators are required for this test. See the illustrations below for possible configurations.
  4. 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.

  5. 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

The illustrations below show the recommended M9381A PXIe signal generator. If your setup is using the alternative M9380A PXIe signal generator, refer to the M9380A Startup Guide for the default cable interconnections.

To view the image, choose from the links below depending on your setup.

ClosedTwo PXIe signal generators for both sources

 

ClosedPXIe signal generator as source 1, and a PSG-D signal generator as source 2

 

ClosedPSG-D signal generator as source 1, and a PXIe signal generator as source 2

 

ClosedPSG-D signal generator as both source 1 and source 2