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Introduction of electric wave darkroom

Release time:

2022-11-02 13:24

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Introduction of the radioactive dark room.

Generally speaking, for radiation testing, there are three test sites, namely, fully anechoic chamber, semi-anechoic chamber and open site. In general, the radiation test conducted in these three test sites can be considered to be in line with the laws of electromagnetic wave propagation in free space, so what is the introduction of the electric wave dark room?

Characteristics of the electric wave darkroom.

1. Electric wave darkroom reduces the interference of external electromagnetic signals on the test signal, electromagnetic wave absorption materials can reduce the reflection of the walls and ceiling on the test results caused by multipath effect, suitable for emission, sensitivity and immunity experiments. In practical applications, if the shielding effectiveness of the shielding body can reach 80dB~140dB, the interference to the external environment can be negligible, and the free space can be simulated in a completely anechoic chamber. Compared with the other two test sites, the fully anechoic dark room has few reflections from the floor, ceiling and walls and is subject to little interference from the outside environment and is not affected by outside weather. Its disadvantage is that it is limited by the cost and test space.

2. The half-wave darkroom is similar to the full-wave darkroom. It is also a hexagonal box, which has a shielding design and electromagnetic wave absorption materials. The difference is that the semi-wave darkroom uses a conductive floor instead of wave-absorbing material. The semi-wave darkroom simulates an ideal open field, i.e., the field has an infinite geodesic plane with good conductivity. In the semi-wave darkroom, since the floor is not covered with absorbing material, a reflection path will be generated, so that the signal received by the receiving antenna will be the sum of the signals from the direct and reflected paths.

3. An open field is a flat, open, elliptical or circular test field with uniform conductivity and no reflector. The ideal open space has good conductivity and an infinite area. The signal received by the receiving antenna between 30 MHz and 1000 MHz will be the sum of the direct path and reflected path signals. However, in practice, although good ground conductivity can be obtained, the limited open field area may cause phase differences between the transmitting and receiving antennas. In the transmit test, the open field is used in the same way as in the semi-wave darkroom.

What are the requirements of the radio wave darkroom?

1. A darkroom is a measurement site that simulates the open field used for EMC measurements, providing a clean electromagnetic background and good field uniformity. The darkroom is generally used at frequencies around 9KHz~40GHz. Let's take a look at the common index requirements for three-meter and ten-meter radio wave darkrooms.

2. In order to meet the normalized field attenuation law of 30 MHz ~ 40 GHz, the general darkroom needs to use ferrite sheet and carburized foam corner cone or hollow corner cone composite or polyurethane foam wedge wave absorbing material of broadband absorbing material.

3. Chopper: wave-absorbing materials for electromagnetic wave absorption effect is usually applied to more than 450MHz, and high temperature resistance, high field strength.

4. Ferrite: the electromagnetic wave absorption effect of ferrite is below 1GHz, preferably below 500MHz. Let's take a look at the difference between the two dark rooms.

5. From the above table, we can see that compared with the 3m radio darkroom, the 10m radio darkroom has obvious advantages: larger structure of the radio darkroom, larger diameter of the turntable, larger carrying capacity, smarter receiving antenna direction, wider test blind area, and smaller test error at low frequency. Let's analyze the impact of the above on our test samples.

What are the advantages of the anechoic chamber of the electric wave dark room?

1. The large diameter of the turntable and the high carrying capacity allow you to measure heavier samples. If the sample is more than 1 ton, please choose the 10m electric wave darkroom.

2. Larger static area allows you to measure samples with larger appearance. If the sample diameter is more than 1.5m, please choose 10m electro-wave darkroom.

3. Fewer errors and more accurate and authoritative data. Note: At present, many countries or regions below 1GHz radiation harassment data have not received the test results of the 3m radio wave darkroom. That is, if the test frequency of radiation harassment is less than 1GHz, please choose the 10m electric wave darkroom.

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