EMI Emissions Testing

Radiated emissions testing measures the radiated disturbance field strength emitted by the EUT (Equipment Under Test) through space. It can be divided into:

- Magnetic Field Radiation: Mainly used for lighting devices and induction cookers;

- Electric Field Radiation: More widely applied;

- Disturbance Power: Suitable for household appliances, power tools, and AV product auxiliary devices.

1. Radiated Emissions Testing Standards

a) Electric Field Radiation Standards:

- CISPR22

- CISPR13

- CISPR11

- CISPR14-1

- CISPR15 (for specific types of toys)

b) Magnetic Field Radiation Standards:

- CISPR15 (for lamps with operating current frequencies >100Hz)

- CISPR11 (for induction cookers)

c) Disturbance Power Standards:

- CISPR14-1 (excluding devices with operating frequencies ≤9kHz)

- CISPR13 (only for auxiliary devices)

2. Radiated Emissions Testing Methods

1. Test Instruments and Equipment:

a) Electric Field Radiation:

- Receiver (for frequencies below 1GHz)

- Spectrum analyzer (for frequencies above 1GHz)

- Anechoic chamber

- Antennas:

- Below 1GHz: Biconical antenna + Log-periodic antenna / Broadband composite antenna

- Above 1GHz: Horn antenna

b) Magnetic Field Radiation:

- Receiver

- Tri-axis loop antenna / Single small loop far-field antenna

c) Disturbance Power:

- Receiver

- Power absorption clamp

Standards Requirements:

- Receiver: CISPR16-1-1

- Antennas and Site: CISPR16-1-4

- Absorption Clamp: CISPR16-1-3

2. Test Setup:

a) Electric Field Radiation:

- Differentiate between desktop and floor-standing devices;

- Similar to conducted emissions setup;

- All devices and cables must be arranged strictly according to the standards;

b) Magnetic Field Radiation:

- Tri-axis loop antenna: For EUTs with lengths <1.6m (antenna diameter 2m);

- For induction cookers longer than 1.6m: Use a 0.6m diameter single loop far-field antenna at a distance of 3m, with a minimum height of 1m (CISPR11);

c) Disturbance Power:

- Desktop: Place on a non-metallic tabletop at a height of 0.8m, with a distance of ≥0.8m from metallic objects (or ≥0.4m, CISPR14-1);

- Floor-standing: Place on a non-metallic stand at a height of 0.1m;

- Test cables (LUT):

- Place on an absorption clamp rail 0.8m high and 6m long;

- Absorption clamp should be on the cable, with the current transformer end facing the EUT;

- Cables that can be disconnected should be broken; non-disconnectable cables should be isolated with ferrite clamps.

3. Test Frequency Range:

- Electric Field Radiation: 30MHz–1GHz (some standards require >1GHz)

- Magnetic Field Radiation: 9kHz–30MHz

- Disturbance Power: 30–300MHz

4. Test Limits:

- Test distance may vary depending on the standard: 3m, 10m, or other distances;

- Limits are related to product categories (Group 1/2, Class A/B).

5. Testing Process:

a) 30MHz–1GHz Electric Field Radiation:

- Semi-anechoic chamber;

- EUT rotates 360° on a turntable;

- Antenna height 1–4m, vertical and horizontal scanning to find the maximum value;

- Use QP (quasi-peak) detector;

- Test both vertical and horizontal polarization directions.

b) >1GHz Electric Field Radiation:

- Applicable to:

- ITE devices: Operating frequency >108MHz;

- ISM devices: Operating frequency >400MHz;

- Test site: 3m;

- Use spectrum analyzer, with results based on Peak and Average values;

- ITE method is similar to the 30MHz–1GHz range;

- ISM devices:

- Test in a full-anechoic chamber;

- Antenna height fixed at the same level as the EUT;

- Antenna does not move, while EUT rotates to find the maximum value.

c) Alternative Method (ERP Calculation):

- Used for testing the radiation of the enclosure;

- Remove detachable cables; for non-detachable cables, use ferrite clamps for isolation;

- Steps:

1. Measure maximum value with Antenna A and receiver;

2. Replace EUT with Antenna B, connect signal source, and adjust to the same output;

3. Record the input power of Antenna B, which is the enclosure radiation power.

d) Magnetic Field Radiation:

- Tri-axis loop antenna: Place the test sample at the center of the antenna;

- Measure X/Y/Z directions;

- Single small loop antenna: Place it vertically on the ground, at a minimum height of 1m;

- Measure the horizontal and vertical magnetic field components of the EUT.

e) Disturbance Power:

- All cables (>25cm) must be tested;

- Disturbance appears as standing wave distribution in the 30–300MHz range;

- Move the absorption clamp during testing to find the maximum value (typically at the half-wavelength position).

3. Test Results Evaluation

- Below limit line: PASS

- Exceeds limit line: FAIL

4. Test Considerations

- The test setup is critical;

- High-frequency testing has high requirements for the site and equipment, which significantly impact results.

5. Test Frequency Range Summary

30MHz – 18.5GHz

JJR Laboratory, China, provides testing services. Feel free to contact us for inquiries.