RadiMation Application Note 147

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

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

The following devices are necessary to execute this test:

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

Configuration of the testsite

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

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

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

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

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.

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 ($\mu _{0}$) in Henry's per meter (H/m). For free space, the permeability is given as: $\mu _{0}[H/m]=4\pi \cdot 10^{-7}$ $B[T]=\mu _{0}*H[A/m]$ Converting from T to pT and from A/m to µA/m, and converting it to decibels, using the Log, the constant becomes: $240-120+20log^{10}(4\pi \cdot 10^{-7})=1.984$ (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:

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

Perform the test

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

    Tests

       Radiated Emission

          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.

Start

The start frequency of the test. For example 30 kHz.

Stop	The stop frequency of the test. For example 100 kHz.

Reference Level

The reference level set in an analyser, not used in a receiver

Attenuation

The attenuation set in the receiver

RBW	The RBW set in the receiver, see table with different bands for possible values

Step size

The step size set in the receiver, see table with different bands for possible values

Measure time

The measure time set in the receiver, see table with different bands for possible values

Preamplifier

The preamplifier setting set in the receiver

Traces

The type of trace set in the receiver, for MIL-STD RE101 a peak detector is used

Test Equipment

The equipment used for the measurement, see table with different bands for possible values

Location type

Set this to Magnetic Field antenna

Max Height

The maximum height for the antenna tower, configuration is depending on how many positions should be measured

Min Height

The minimal height for the antenna tower, configuration is depending on how many positions should be measured

Steps

The number of height positions to measure, configuration is depending on how many positions should be measured

Move during measurement

If the antenna tower can move during the measurement, not used during MIL-STD RE101 measurement

Optimize Height

Find the optimal emission around a certain height, not used during MIL-STD RE101 measurement

Distance

The used antenna distance, 7cm for MIL-STD RE101

Antenna Polarization

Which polarization is used, Vertical, Horizontal or Both, above 30 MHz both polarization should be tested

Start Angle

The minimal turn table angle

End Angle

The maximum turn table angle

Steps

The number of angles to measure

Turn during measurement

If the turn table can move during the measurement, not applicable for MIL-STD RE101

Optimize Angle

Find the optimal emission around a certain angle, not applicable for MIL-STD RE101

EUT Angle Offset

The offset of the EUT on the table, not applicable for MIL-STD RE101

Limit Lines

The applicable limit line can be added, in this case "MIL-STD-461G RE101-2 Navy Applications"

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

Peak detection

How many peaks should be detected automatically, no peaks should be measured for MIL-STD RE101

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

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.

Conclusion

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^®.

Equipment Under Test

Line Impedance Stabilisation Network

Decibel

Resolution BandWidth