RadiMation Application Note 156

How to perform a radiated emission substitution test

This application note explains how to perform a radiated emission substitution test with RadiMation^®, as for example mentioned in ETSI EN 300-320 C5.3 and C5.4

The exact requirements and test methods for the ETSI EN 300-320 are specified in the ETSI EN 300-320.

Necessary equipment

The following devices are necessary to perform a radiated emission substitution test:

• Signal generator
• Transmitting Antenna
• Receiving Antenna
• Receiver/spectrum analyzer as FWD power meter or a FWD power meter
• Coupler (0 dB coupling factor)

General remarks

• For higher quality and accuracy, it is still advised to use normal practices like powermeter zeroing and calibration

• Cabling and system setup of all components from the receive antenna to the reciever that is used during Phase B, should be exactly the same during the normal emission measurements. Changes in cabling or antenna should result in a redetermination of the antenna correction.

Performing the measurements

There are three phases (A, B & C) to determine the correct antenna factor

Phase A: Determine the power being applied to the antenna

Purpose

Purpose of this phase is to determine the power that is going into the transmit antenna during Phase B.

Very often an attenuator is used between the signal generator and the antenna, to reduce mismatches.

This phase is used to correct for cable, attenuator and signal generator losses.

Set up

• A1. Build a setup with signal generator outside the chamer and the transmit antenna in the chamber

• A2. Do not connect the transmit antenna yet, but connect the receiver on the location of the transmit antenna

• A3. Sweep with a RI Fixed power test 0 dBm signal power over the frequency range. The antenna selected in the testsite of this test is not relevant. A coupler with a 0 dB coupling factor should also be used

• A4. Also measure the forward power using the receiver

The powervalues measured as the forward power meter are the power values that are applied to the transmit antenna during phase C

Phase B: Determine the overall transfer of the measurement system

Purpose

Purpose of this phase is to measure the overall transfer from the transmit antenna to the receiver

Set up

• B1. Build a setup with signal generator outside the chamber and the transmit antenna in the chamber

• B2. Place the receiver outside the chamber and connect it to the receive antenna in the chamber

• B3. Sweep with a RI Fixed power test 0 dBm signal power over the frequency range. This can be the same test configuration as is used during step A3.

The antenna selected in the testsite of this test is not relevant.

A coupler with a 0 dB coupling factor should also be used

• B4. Also measure the forward power using the receiver

The power values measured as the forward power meter will be used to determine the correct correction factor

Phase C: Calculate the correct antenna correction factor

Purpose

Purpose of this phase is to use the measurement results obtained during phase A and B to determine the correction factor for the total system that can be used during an emission substitution measurement

Calculation

For each frequency use the following calculation:

C = P_transmit + G_dipole - P_transfer

P_transmit: The forward power during Phase A G_dipole: the Transmit Antenna Factor of the transmit antenna compared to a dipole P_transfer: The forward power during Phase B

The G_dipole can be calculate from the calibrated Antenna Factor of the transmit antenna with:

G_dipole = 20 * log10(f) - AF - 29.79 - 2.15

f: The frequency, expressed in MHz AF: The antenna factor of the antenna, expressed in dB/m (The factor 2.15 is to correct from an isotropic antenna to a dipole antenna)

Application

The determined C can be used as the correction of the antenna during the real measurement, and can be placed in a correction file that is attached to the receiving antenna.

The measurement with the EUT

On the location of the transmit antenna the EUT is positioned. The determined antenna correction factor (C) should be applied to the antenna that is used in the testsite during the measurement No other corrections should be included in the testsite. Correction of the cables, preamplifiers and attenuators should not be done, because all these components also have been present during phase B, and are thus already corrected for in the determined antenna correction factor (C).

Perform a multiband radiated emission measurement, with the 'Antenna Spurious and harmonics' location type The values that are measured are the correct Effective Radiated Power measurements.

conclusion

This application note outlines a three-phase process for determining the antenna correction factor in emission substitution measurements using RadiMation.

By systematically addressing power application to the antenna, measuring the overall transfer of the measurement system, and calculating the correct correction factor, users can achieve precise and reliable results.

The provided formulae and guidelines offer a methodology for calibrating the system, ensuring accurate measurements in real-world scenarios.

It is crucial to adhere to the general remarks, maintaining consistency in setup and utilizing calibrated antenna factors.

This application note serves as a comprehensive guide, empowering users to perform these emission substitution measurements with confidence and accuracy.

Decibel

Radiated Immunity

Power expressed in milliWatt in dB values.

• 1 mW = 0 dBm

• 2 mW = 3 dBm

• 100 mW = 20 dBm

• 1 W = 30 dBm

• 100 W = 50 dBm

Equipment Under Test