Electromagnetic compatibility test for radiation harassment
Radiated harassment is part of the EMI test, and the intensity of radiation harassment is assessed by standard measurement methods and measurement equipment. The characteristics of the test site will directly affect the results of the radiation measurement, so the effectiveness of the site should be ensured and the consistency of the measurement should be ensured.
(1) Test equipment, facilities and requirements
A) oval open field or semi-anechoic chamber and all-electric darkroom: | NSAmeasured-NSAthe nitride | ≤4, SVSWR≤6.
B) Measurement receiver: 30MHz ~ 18GHz frequency range, with peak, quasi-peak, the average detection, to meet the CISPR16-1-1 related requirements.
C) broadband antenna: 30MHz ~ 1GHz frequency range
Horn antenna: 1GHz above the frequency range
(2) measuring distance
U EUT shall be measured at a specified distance corresponding to the radiation disturbance limit unless the measurement can not be achieved due to factors such as the size of the equipment.
U The different criteria are different for measuring the distance: for example, the measurement distance specified by EN55032 (EN55022) refers to the horizontal distance of the EUT's hypothetical boundary to the test antenna test reference point; the measurement distance specified by EN 55013 is the test antenna test The horizontal distance between the reference point and the imaginary radiation center of the device under test. When the distance is 10m, both methods can be used.
U In most outdoor venues, a distance of 10 m is preferred because the estimated level of disturbance at this distance is much higher than the general ambient level allowed to be tested.
(Usually do not use less than 3m or greater than 30m distance.)
(3) antenna height change
For magnetic field strength measurements, the height of the receiving antenna can be fixed at a specified elevation (typically 1 m from the ground to the bottom of the loop antenna) when using a single-ring magnetic field antenna. The ring antenna or EUT should be rotated in order to find the maximum detected disturbance.
If the ambient level at some frequencies within the specified measurement range exceeds the limit, the following alternative method can be used:
A) Measure at a closer distance and then convert the measurement to the specified limit, the conversion formula should be recommended in the product (class) EMC standard, or at no less than three different distances Verified by measurement.
B) When the radio station is off the air and the ambient level of the industrial equipment is low, the original environment level exceeds the specified frequency band.
C) In the shielded room or the shielding room with the absorbing material, the disturbance frequency of the EUT at the test frequency is compared with the disturbance amplitude at the adjacent frequency, and the measured frequency of the adjacent frequency can be compared with the measured frequency
Distortion amplitude to estimate the disturbance rate of the EUT at the test frequency.
D) When determining the axis of the open test field, consider the direction of the strong ambient signal so that the direction of the receiving antenna on the test field is distinguished as much as possible.
E) Narrow-band harassment of EUT near the RF signal may be measured with a narrower instrument bandwidth when both fall into the standard frequency band.
