tell you about the knowledge introduction of shielding boxes

Introduction to Shielded Boxes

1、 Main features:

1. Adopting upper and lower covers and double slot shielding, the isolation frequency can reach over 3GHz;

2. The action mode can be automatic (serial port control) or manual (button control);

3. All data ports and power signals use EMI filters;

4. The test results PASS/FAIL can be displayed through red and green LEDs;

5. Equipped with anti pressure hand function

Principle

Simply put, it means absorbing interference internally and shielding electromagnetic signals externally.

1、 Utilizing the principle of electromagnetic induction in circuit theory

When an alternating electromagnetic field passes through the surface of a metal material, the metal material will form eddy currents due to the induced electromotive force. The magnetic field generated by this eddy current is exactly opposite to the original magnetic field direction, thereby offsetting some of the original magnetic field and playing a shielding role. In addition, due to the certain resistance of metal materials, eddy currents generate heat inside the metal material, which partially consumes the ability of incident electromagnetic waves and also plays a shielding role.

2、 According to electromagnetic field theory

The electromagnetic wave will be reflected at the interface of different propagation media due to the sudden change of wave impedance. In addition, in the transmission medium, such as inside metal materials, electromagnetic waves will undergo attenuation. This reflection and attenuation effect precisely illustrates the shielding mechanism of metal materials.

3、 It's based on transmission line theory

Electromagnetic waves in lossy non-uniform transmission lines may experience reflection due to impedance mismatch between the transmission line and the electromagnetic wave. Additionally, the transmission line is lossy and the electromagnetic wave will undergo attenuation during transmission. This is very similar to the reflection and attenuation in the theoretical analysis of electromagnetic waves, but this method is much simpler than the analysis method of electromagnetic waves, and is currently the most widely used method in electromagnetic shielding analysis.

When electromagnetic waves incident on a metal plate, reflection occurs, which is called reflection loss from the perspective of shielding. The part of the transmitted wave that decays and is lost during transmission inside the metal plate is called absorption loss. The electromagnetic waves reflected on the second interface are reflected and transmitted again at the first interface, repeating until they are completely consumed. This phenomenon of multiple reflections is called the multiple reflection correction factor. The principle of double-layer shielding in shielding boxes

Sometimes, in order to increase the shielding effect, a double-layer shielding scheme can be adopted. However, the correction factor C is negative, which mainly reflects that after multiple reflections of electromagnetic waves in the space between the two shielding layers, a considerable portion penetrates the second shielding layer and enters the internal space, resulting in a decrease in shielding effectiveness. In addition, the space between the two shielding layers may also cause resonance, which can have a negative impact on the double-layer shielding. In addition, it should be noted that the two shielding layers should be separated to prevent the ground current above the outer shielding layer from affecting the inner shielding layer and reducing the shielding effectiveness of the double layer shielding.

The testing of wireless terminal products cannot be separated from shielded boxes, so choosing high-quality and reliable products can ensure the accuracy of one's own equipment.

The shielding box is made of conductive or magnetic materials and is mainly suitable for testing wireless communication products, such as mobile phones, wireless network cards, wireless data cards, wireless routers, WIFI, and other related products.

The basic meaning of a shielding box: A shielding box is a metal body made of conductive or magnetic materials in various shapes, which limits electromagnetic capabilities to a certain spatial range and is used to suppress radiation interference. And it is a device that processes conduction and radiation to provide a non-interference testing environment for the tested wireless communication equipment.

Shielding effect:

One is to limit the radiated electromagnetic energy inside the equipment to exceed a certain area, i.e. absorb internal interference signals;

The second is to prevent external radiated electromagnetic energy from entering a certain area, that is, to shield external interference signals.

Shielding concept: refers to the simulation of interference sources placed outside the shielding box, where the ratio of electric field strength, magnetic field strength, or power at a certain point in the space before and after the shielding box is placed is taken as a logarithm (lgp1/p2), expressed in dB.

Detection equipment: network analysis, signal generator, spectrum analyzer, dipole antenna, horn antenna, shielding box.

Classification: It can be divided into manual shielding boxes, pneumatic shielding boxes, and fully automatic shielding boxes according to different testing requirements.

1. The manual shielding box is easy to operate. Test devices such as mobile phones, laptops, and PADs have corresponding sizes. Suitable for research and development, testing, certification, and other institutions. 2. Pneumatic shielding boxes are often used in production testing, improving testing efficiency and reducing operator fatigue. Test devices such as mobile phones, laptops, and PADs have corresponding sizes.

3. The fully automatic shielding box controls the testing shielding box according to communication instructions through the international standard RS-232 interface to complete the entire testing process. It is generally used for small RF modules and large-scale production lines to improve production efficiency.

For wireless communication product manufacturers, the inability to market or quickly increase the quantity of products in a timely manner results in a significant loss of output value and profits. Directly affect the expansion of subsequent business and market share.

The RF testing process is usually the most complex and influential process in the production line of wireless communication devices such as mobile phones, and it is also a bottleneck in the production line. RF testing stations are usually composed of testing instruments, shielding boxes, testing software, and can be divided into calibration testing, comprehensive testing, antenna testing, and other categories. Due to production capacity requirements, the RF testing process is usually run in parallel by multiple identical testing stations. The pass rate of one or some testing stations is low; A decrease in output can lead to bottlenecks in the production line and a sharp increase in production costs. The reasons can be roughly divided into: product design or material reasons, testing issues (mistesting issues), environmental factors such as radio frequency interference, and testing uncertainty. Electromagnetic interference/EMI is a problem that the entire electronic field must face and overcome. Generally, in wireless communication products such as mobile phones, wireless network cards, wireless routers, wireless headphones, Bluetooth headphones, Wi Fi, Wimax, data cards, walkie talkies, RFID, and other wireless communication devices and modules, the testing environment is improved through the use of RF test shielding boxes during board and final testing.

The shielding box is used to isolate external base station signals and external interference signals.

Absorb the RF signal inside the box to reduce interference.

Reduce the impact of personnel and make testing more accurate.

Save operating time and improve work efficiency.

Isolate interference from adjacent test equipment.

Integrate multiple testing processes, simplify processes, and improve efficiency.

Application scope:

1. Application wireless communication testing

2. EMI testing

3. Coupling testing

4. RF functional testing

5. Receiver sensitivity test

6. Transmitter radiation power test

7、Bluetooth，DAB/DM

8. EMI and EMS testing of small UHF equipment

9. Testing of mobile phones, Bluetooth, wireless routers, and other devices, as well as the entire machine or chip

The different functions of pneumatic and manual shielding boxes

The pneumatic shielding box can isolate external base station signals and external interference signals. Absorb the RF signal inside the box to reduce interference. It can reduce the impact of personnel and make testing more accurate. Another aspect is to save operating time and improve work efficiency. The integration of multiple testing processes simplifies the process, improves efficiency, and can isolate interference from adjacent testing equipment. The manual shielding box is made of conductive or magnetic materials and is mainly suitable for testing wireless communication products, such as mobile phones, wireless network cards, wireless data cards, wireless routers, WIFI, and other related products. The purpose of using shielding in manual shielding boxes is to limit the radiation electromagnetic energy inside the equipment to exceed a certain area. Secondly, it is to prevent external radiated electromagnetic energy from entering a certain area. A metal body made of conductive or magnetic materials, plates, sleeves, and other shapes of shielding materials, which limits electromagnetic capabilities within a certain spatial range to suppress radiation interference, and processes conduction and radiation to provide a non-interference testing environment for the tested wireless communication equipment. In electronic equipment production enterprises, shielding boxes are essential, and the shielding boxes required for each different field are different, such as GPS shielding boxes, mobile signal shielding boxes, Bluetooth shielding boxes, manual shielding boxes, pneumatic shielding boxes, and mobile phone shielding boxes. The selection of shielding boxes is also very important, and the most important thing is safety and reliability. So when choosing, you can choose based on the different aspects of the shielding box's function.