RadiMation Application Note 147

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How to perform a MIL-STD-461 RE101 Radiated Emission test[edit]

This application note explains how the MIL-STD-461 RE101 Radiated Emission test can be performed with RadiMation®.

The "RE101, radiated emissions, magnetic field" test is applicable to equipment, subsystem enclosures and all interconnecting cables and is used to verify that the magnetic field emissions from the EUT and cabling do not exceed the specified requirements.

The exact requirements and test methods for the RE101 are specified in the MIL-STD-461.

Necessary equipment[edit]

The following devices are necessary to execute this test:

  • Receiver
  • Loop sensor (Antenna)
  • LISN
  • Cable

Configuration of the testsite[edit]

The configuration of the testsite is a loop sensor antenna connected with a cable to a receiver.

RE101 Test layout.png

The configuration of the testsite should thus contain the following devices:

Device name Tab in testsite configuration window note
Antenna Devices 1 Loop sensor antenna for the required frequency range
Spectrum Analyser Devices 2 The receiver used for the test
Cable preamp -> analyser Cables Cable with a correction file specified for the loss
Information.png
Note: The LISN is only used to decouple the EUT and it is not needed to specify and configure this in RadiMation®

Configuration of the loop sensor antenna[edit]

The loop antenna needs to have the correction data applied, which is normally known by the manufacturer. The correction data is expressed in dBpT/µV.

In RadiMation® this can be configured by creating a correction file, which contains a Frequency and a Correction column. The frequencies and the correction values of the actual correction of the loop antenna can then be specified in the correction file. The values in the Correction column in the correction should be expressed in dBpT/µV.

Convert k-factor from dB(S/m) or dB(/Ohm m) to dBpT/µV[edit]

Some calibration certificates of loop antennas contain the magnetic field factor of the loop antenna as a k-factor with a dB(S/m) unit (which is the same as a dB(/Ohm m) unit). RadiMation® expects however expect that the values in the correction file are expressed in the dBpt/µV unit.

The conversion is: 'MagneticFieldFactor [dBpT/µV] = k [dB(S/m)] + 1.984'. The value 1.984 is often simplified to be 2.0, but 1.984 is the more accurate value.

Information.png
Note: The relation between dBpT and A/m is: Magnetic Flux Density [dBpT] = Magnetic field [dBµA/m] + 1.984

In this equation, the constant 1.984 is derived by using: The magnetic flux density (B) in Tesla (T), is related to the magnetic field strength (H) in A/m, by the permeability of the medium () in Henry's per meter (H/m). For free space, the permeability is given as:

Converting from T to pT and from A/m to µA/m, and converting it to decibels, using the Log, the constant becomes:

(to be exact: 1.9841972804419248955749215547977)

Also see: https://www.tf.uni-kiel.de/matwis/amat/elmat_en/kap_4/backbone/r4_1_1.html

An example correction file for this 'Magnetic Field factor' thus looks like:

RE101 Correction.png

Once this correction is stored to disk, this correction file can be selected in the loop antenna driver configuration as 'Magnetic Field Factor':

RE101 Loop configuration.png

Perform the test[edit]

To perform the actual RE101 test, start a Radiated Emission Multiband test:

   Menu.svg Tests
      Menu.svg Radiated Emission
         Menu.svg Multiband

The complete test from 30 Hz up to 150 kHz has different settings for different frequency bands. All these different bands can be configured. The test can be configured with 3 bands, each using their applicable frequency range, measure time and bandwidth.

Band Frequency range RBW Step size Measure time receiver Measure time FFT receiver
Band 1 30 Hz - 1 kHz 10 Hz 5 Hz 0.15 s 1 s
Band 2 1 kHz - 10 kHz 100 Hz 50 Hz 0.015 s 1 s
Band 3 10 kHz - 150 kHz 1 kHz 500 Hz 0.015 s 1 s

In the following screenshot a configuration is shown to perform the measurement on an EUT, applicable for the Navy Application.

The Location type setting for every band should be set to Magnetic Field antenna, as that determines that the measurement result will be shown as magnetic field values.

RE101 Test configuration.png


ScreenElementDescription.svg Start The start frequency of the test. For example 30 kHz.
ScreenElementDescription.svg Stop The stop frequency of the test. For example 100 kHz.
ScreenElementDescription.svg Reference Level The reference level set in an analyser, not used in a receiver
ScreenElementDescription.svg Attenuation The attenuation set in the receiver
ScreenElementDescription.svg RBW The RBW set in the receiver, see table with different bands for possible values
ScreenElementDescription.svg Step size The step size set in the receiver, see table with different bands for possible values
ScreenElementDescription.svg Measure time The measure time set in the receiver, see table with different bands for possible values
ScreenElementDescription.svg Preamplifier The preamplifier setting set in the receiver
ScreenElementDescription.svg Traces The type of trace set in the receiver, for MIL-STD RE101 a peak detector is used
ScreenElementDescription.svg Test Equipment The equipment used for the measurement, see table with different bands for possible values
ScreenElementDescription.svg Location type Set this to Magnetic Field antenna
ScreenElementDescription.svg Max Height The maximum height for the antenna tower, configuration is depending on how many positions should be measured
ScreenElementDescription.svg Min Height The minimal height for the antenna tower, configuration is depending on how many positions should be measured
ScreenElementDescription.svg Steps The number of height positions to measure, configuration is depending on how many positions should be measured
ScreenElementDescription.svg Move during measurement If the antenna tower can move during the measurement, not used during MIL-STD RE101 measurement
ScreenElementDescription.svg Optimize Height Find the optimal emission around a certain height, not used during MIL-STD RE101 measurement
ScreenElementDescription.svg Distance The used antenna distance, 7cm for MIL-STD RE101
ScreenElementDescription.svg Antenna Polarization Which polarization is used, Vertical, Horizontal or Both, above 30 MHz both polarization should be tested
ScreenElementDescription.svg Start Angle The minimal turn table angle
ScreenElementDescription.svg End Angle The maximum turn table angle
ScreenElementDescription.svg Steps The number of angles to measure
ScreenElementDescription.svg Turn during measurement If the turn table can move during the measurement, not applicable for MIL-STD RE101
ScreenElementDescription.svg Optimize Angle Find the optimal emission around a certain angle, not applicable for MIL-STD RE101
ScreenElementDescription.svg EUT Angle Offset The offset of the EUT on the table, not applicable for MIL-STD RE101
ScreenElementDescription.svg Limit Lines The applicable limit line can be added, in this case "MIL-STD-461G RE101-2 Navy Applications"
ScreenElementDescription.svg All peaks above x dB below the limit line Which level above x dB below the limit line should detect peaks, no peaks should be measured in MIL-STD RE101
ScreenElementDescription.svg Peak detection How many peaks should be detected automatically, no peaks should be measured for MIL-STD RE101
ScreenElementDescription.svg Final peak measurement It is possible to perform a final measurement on a peak with a specific detector, no final peak measurement is needed for RE101


When all parameters are configured for the RE101 test, press Start Test to perform the emission measurement.

Review the initial scan and measure frequencies for maximum emission[edit]

With the the frequencies of maximum emission located, add the frequencies as peaks by clicking in the graph. A list of peaks with frequencies should appear below in the Peaks tab. As described in section 5.17.3.4c(4) and 5.17.3.4c(5) it is needed to find the maximum radiation, the following steps describe how to perform this within RadiMation.

To measure one single frequency and find the maximum radiation:

  1. Select one frequency by checking one single frequency in the peaks list.
  2. Click Peak Actions and select Set receiver to Peak settings to set the correct measure time and RBW as configured.
  3. Enable Continuous Measure and move the loop antenna to find the maximum radiation.
  4. Click Continuous Measure again to stop the measurement.
  5. Repeat this step for each frequency.

RE101 Test measure peak.png

Conclusion[edit]

The MIL-STD RE101 test is using different receiver settings depending on the frequency band to cover the measurement of the magnetic field for the complete frequency range. All these settings can be easily configured in a multiband "Test Setup File" and tested with RadiMation®.