Radiated Emission Test

Radiated Emission (Radiated Emission) test is to measure the intensity of the radiated nuisance field propagated by the EUT through space. It can be categorized into magnetic field radiation, electric field radiation, the former for lamps and induction cookers, and the latter for common applications. In addition, home appliances and power tools, auxiliary equipment for AV products have power radiation requirements (called nuisance power).

1. Radiated emission test standards.

a) Electric field radiation: CISPR22, CISPR13, CISPR11, CISPR14-1, CISPR15 (specific categories of toys);

b) Magnetic field radiation: CISPR15 (lamps and lanterns with an operating current frequency exceeding 100Hz), CISPR11 (induction cookers);

c) Nuisance power: CISPR14-1 (except for a part of equipment whose operating frequency does not exceed 9kHz), CISPR13 (auxiliary equipment only).

2. Radiated Emission Test Methods

1) Radiated emission test instruments and equipment:

a) Electric field radiation: receivers (1G or less), spectrometers (1G or more), radio wave darkroom, antennas (1G or less generally use double

cone and logarithmic cycle combination or with broadband composite antenna, 1G and above horn antenna);

b) Magnetic field radiation: receivers, three-ring antennas or single small-ring distant antennas;

c) Nuisance power: receivers, power absorbing clamps.

The receiver follows the requirements of CISPR16-1-1, the antenna and site follow the requirements of CISPR16-1-4, and the absorbing clamp follows the requirements of CISPR16-1-3.

2) Radiated Emission Test Test Layout:

a) electric field radiation: also divided into tabletop and floor-standing, the same as conducted emissions (because the relationship between radiated emission results and product layout)

(Because the radiation emission results and product layout is particularly close, so we need to strictly follow the standard layout, including products, auxiliary equipment, all cables, including the sample under test);

b) magnetic field radiation: different sizes of three-ring antenna to be able to test the maximum size of the EUT is limited to 2m diameter ring three-ring antenna, for example, the length of less than 1.6m EUT can be placed in the center of the three-ring antenna to test; in the CISPR11, more than 1.6m of the induction cooker with a 0.6m diameter of the single-ring far antenna in 3m away from the measurement of the minimum height of 1m;

c) nuisance power: divided into desktop and floor-standing, desktop equipment on a non-metallic table of 0.8m, at least 0.8m away from other metal objects (usually shielded room of the metal inner wall, this distance is required in CISPR14-1 is at least 0.4m); floor-standing equipment placed on a non-metallic support of 0.1m; the cable under test (LUT) is arranged in the height of 0.8m, the length of the power absorber 6m The cable under test (LUT) is arranged on a 0.8m high, 6m long power absorber clamp rail, with the absorber clamp on the cable and the current transformer end facing the device under test. If the device under test has other cables, it can be disconnected without affecting the function of the case of disconnection, can not be disconnected with ferrite absorber clamp isolation.

3) Radiation emission test band: electric field radiation is generally 30MHz-1GHz (some products need to be measured more than 1G, according to specific standards), magnetic field 9kHz-30MHz, nuisance power 30-300MHz.

4) Radiation emission test limits: with different standards, the site is 3m, 10m or other sizes, different product classification (Group 1/2, Class A/B) and different limits.

5) Radiated Emission Test Procedure:

a) 30MHz-1GHz electric field radiation: conducted in a semi-electrical wave dark room, the EUT rotates 360 degrees with the rotary table, and the antenna is at a height of 1-4m

up and down to find the radiation maximum. The results are expressed as QP values. Both vertical and horizontal antenna polarization directions are measured.

b) More than 1G electric field radiation: ITE equipment with operating frequency more than 108MHz and ISM equipment more than 400MHz need to be tested, which is measured in 3m field, using a spectrum meter. ITE equipment testing method is basically the same as 30MHz-1GHz, and the result is expressed by Peak and AV value. The antenna is at the same height as the product, without elevation, and the rotary table is still rotating to find the maximum value of radiation;

c) Substitution method: ERP (Effective Emission Power) is used instead, and then converted to field strength value. This is often used in RF testing, conventional EMC is rarely used. The purpose of the alternative method test is to test the shell radiation of the EUT, which requires the removal of all detachable cables, non-detachable cables on the set of ferrite magnet ring. The maximum nuisance value of the EUT is first measured with antenna A and the receiver, then the EUT is replaced with antenna B. The output power of the signal generator is adjusted until the same value is reached by the measuring receiver. Record the power at the input of the substitute antenna B, which is the case radiated power of the EUT. The selection of antenna is based on the test frequency;

d) magnetic field radiation: the use of three-ring antenna magnetic field radiation test nothing to say, the sample is placed in the center of the antenna, X / Y / Z three directions each measuring a set of magnetic field radiation results. Using a single small ring antenna, the antenna is placed perpendicular to the ground, the lowest part of the ground is higher than the ground 1m, because it is a near-field measurements, and taking into account the reflection of the ground, the measured value reflects the EUT's horizontal and vertical components of the magnetic field;

e) Nuisance power: It is required for all cables of the equipment with a length of more than 25cm (also including cables of auxiliary equipment). Because the nuisance at different frequency points within 30-300MHz is distributed in the form of standing waves in the cable under test. Therefore, the measurement needs to pull the power absorbing clamp along the guide rail to find the location of the maximum nuisance power of each final test frequency (roughly half a wavelength away from the equipment).

3. Radiated emission test result determination:

Still comparing with the limit line. Below PASS, above FAIL.

4. radiated emission test considerations:

Test setup is still the most necessary part of the test. In addition, because it is a high-frequency test, the site, equipment, etc. are very important factors that will affect the final results.

5. Radiated emission test range 30MHz-18.5GH