Power Level Accuracy

Power level accuracy is the difference between the power level indicated by the unit under test (UUT) and the true power delivered by the UUT.

Direct absolute power measurements are made with a power meter for higher power levels. A spectrum analyzer is used for all lower power measurements.

Required Test Equipment

Test Equipment

Recommended Models

Alternate Models

Power Meter

N1914B

N1914A1
N1913A
N1913B

E4418A
E4418B
E4419A
E4419B

Power Sensor

N8482A

E9304A
E9304A H18
E9304A H19

N8482A CFT

8482A2

U8481A Option 200
U8485A Option 200

Spectrum Analyzer

N9030B Opt 5xx4, MPB, Pxx5

N9030A Opt 5xx4, MPB, Pxx5
N9030A/B Opt 5xx4, MPB
N9030A/B Opt 5xx4, Pxx5
N9030A/B Opt 5xx4

E444xA3 Opt 110 and 123
E444xA3 Opt 1DS, 123
E444xA3 Opt 1DS
E444xA3 Opt 110
E444xA3 Opt 123
E444xA3

  1. Power meter N1914A with serial numbers ranging between MY00000000—MY53040007 require Service Note 07 to be applied for measurement repeatability. Please have this service note applied or verify it was applied before using this power meter. The affected service note is N1914A-07.

  2. Not allowed for the following product configurations:

    The dynamic frequency range of this sensor is insufficient for these models.

  3. Depending on your frequency needs, choose either an E4440A, E4443A, E4445A, E4446A, E4447A, or E4448A.

  4. Depending on your frequency needs, choose the option of PXA spectrum analyzer (503, 508, 513, 526, 543, 544, 550) that has a maximum frequency greater than or equal to the maximum frequency of the unit under test.

  5. Select any preamplifier option for the PXA spectrum analyzer (P03, P08, P13, P26, P43, P44, P50) that has a maximum frequency greater than or equal to the maximum frequency of the unit under test.

Connections and Setup Procedures

  • All test equipment requires a 30 minute warm-up period to ensure accurate performance.

  • In the following test setup, cables are designated as solid lines and direct connections are designated as dashed lines.

  • At low power levels, residual spurs from adjacent instruments can cause the UUT to fail the test. Therefore, the instruments must be adequately separated from one another. Do not place one device on top of another. If the test fails at very low power levels, offset all frequencies by +25 Hz or -25 Hz and manually verify. This will shift the test frequency away from possible residual responses.

 

  1. Connect all test equipment as shown.

  2. Connect GPIB cables to all GPIB-controlled test equipment.

  3. While performing this test, follow all instructions on the controller display.

Flexible power sensor channel assignment

This test uses flexible power sensor channel assignment and will identify the channel that a power sensor is connected to using the ability of "smart" sensors such as the N848xA, U848xA, and E930xA series to report their full model and serial number. Legacy 848x series power sensors are unable to provide their model or serial number, but their channel is identified during the sensor calibration process by identifying the channel of the sensor connected to the calibrator.

If the wrong legacy power sensor is connected to the calibrator during this process the error can be resolved by disconnecting and reconnecting the power sensor to the power meter which will force a new calibration.

Select from the links below for connection setups depending on the power sensor.

Power sensor calibration — standard sensors

Power meter measurements (high powers) — standard sensors channel A  

Power meter measurements (high powers) — standard sensors channel B

Low Powers

 

Power sensor calibration — USB sensors

Power meter measurements (high powers) — USB sensors channel C

Power meter measurements (high powers) — USB sensors channel D

Low Powers

 

In Case of Difficulty

  1. Sometimes noise from nearby test equipment can affect low-level measurements. Errors may be caused even if the power meter is stacked on top of the spectrum analyzer.

  2. Inspect all RF cables. If semi-rigid cables are used, check for cracks in the shielding or at the connectors. RF leakage to/from the cables generally cause problems at higher frequencies (> 2 GHz) and low power levels (< -100 dBm).

  3. Verify that the spectrum analyzer does not have a residual spur at the frequency being measured. Sometimes a spur will limit how low in power the spectrum analyzer can measure.

  4. Make sure that all test equipment is using the same power outlet. Ground loops can cause problems at low power levels. This type of problem will most likely show up at lower frequencies.

  5. Make sure all covers on the DUT are secure and that all screws are in place.

  6. Verify the amplifier being used meets its gain specifications.

  7. Make sure all connections in the measurement system are torqued properly. Loose or damaged connections result in RF leakage and errors result at low power levels.

  8. Make sure all test equipment (including the amplifier) has been turned on at least 45 minutes.