At the same time, the insertion loss can also be expressed as: insertion loss (dB) The insertion loss mainly changes with frequency, but due to the characteristics of the ceramic dielectric material making the capacitor, the capacitance will be affected by the use of voltage, temperature and time. The relative change of loss, while the load current saturates the inductive ferrite, also affects the insertion loss. The main commonly used materials of filters used in electrical connectors are: COG (NPO), X7R, Z5U and Y5V. The performance parameters are as follows : Medium classification stability, super stable and stable, general use, rated temperature range, maximum change in temperature range (no voltage applied), media constant aging rate (10 logarithmic time), as can be seen from the table data, if you want to produce with a smaller volume Larger capacity, and its influence on temperature, voltage, frequency and time is relatively stable, X7R is the best material.
According to the filtering principle, we can properly select and design the required filter components, and use a certain connection form to install inside the electrical connector to achieve the purpose of suppressing and absorbing the conducted interference signals.
Shielding is an important means of protection that uses a shield to block or reduce the transmission of electromagnetic energy. Shielding can not only limit the leakage of internally radiated electromagnetic energy ft, but also prevent external radiation from entering a certain area. There are three types of shielding. One is electrostatic shielding: the shield is made of good conductors and has a good ground. In this way, the electric field is terminated on the surface of the conductor, and the induced charge on the surface of the conductor is neutralized by the ground wire to prevent the mutual interference caused by the electrical coupling of the neck. The second is magnetic shielding; the shielding body uses high permeability to form a low reluctance path, which encloses magnetic lines of force in the shielding body to achieve the purpose of blocking the internal magnetic field from diffusing out or being interfered by external magnetic fields. The third is electromagnetic shielding; the use of electromagnetic waves on the surface of the conductor Reflections and sharp attenuation propagating in conductors isolate the mutual coupling of time-varying electromagnetic fields, thereby preventing the interference of high-frequency electromagnetic fields.
In modern electronic and electrical equipment systems, the related functions between components are increasing day by day, which puts strict restrictions on electromagnetic interference. In order to prevent electromagnetic interference, it is necessary to take electromagnetic shielding measures on components. The so-called shielding is to close the electromechanical components with a metal shell to prevent the internal electromagnetic energy from being radiated or interfered by the external electromagnetic field. The shielding effect (S) is defined as the decibel number of the electromagnetic field strength after shielding in a certain area of ​​the space is lower than the electromagnetic field strength before shielding, that is: after research, the shielding effect is not only related to the performance of the shielding material, but also related to the radiation frequency, The shape of the shield is related. The metal shell (shield) has three different mechanisms for the attenuation of electromagnetic waves: When the electromagnetic waves propagating in the air reach the surface of the shield, due to the impedance discontinuity at the interface between the air and the metal, there is a reflection loss effect on the incident wave (R) This reflection has a very small relationship with the thickness of the shield and only requires impedance discontinuities.
The electromagnetic wave energy that is not reflected by the surface and enters the shielding body is absorbed and attenuated by the shielding material when propagating forward in the body (A).
When the remaining electromagnetic wave energy that has not been attenuated in the shielding body reaches the other side of the shielding body, it encounters the impedance discontinuous interface between the metal and the air again, and once again produces a reflection, and refolds back into the shielding body. It may be repeated multiple times between the two interfaces.
Therefore, the shielding effect S can also be determined by the following formula: where B is only studied at the same time, it also shows that the shielding effect of the low frequency band mainly depends on the material of the shield body; Leakage technology, that is to ensure the electromagnetic sealing of the connection gap.
In view of the shielding mechanism, we can choose appropriate shell materials and high conductivity plating layers for electrical connectors to increase the conductive grounding performance of the shell and achieve good electromagnetic shielding in low frequency bands: such as conductive rubber and cables Crimping claws and special shielded cable tails and other technical measures can reduce the "window" exposed by the housing and effectively improve the shielding effect of high-band systems.
Grounding is to connect the shell of the electrical connector to the ground through appropriate methods and methods. This not only improves the stability of the electronic information system and equipment, but also enables a common zero-potential reference surface after the electronic equipment is connected to the ground. So as to effectively suppress the influence of external electromagnetic fields. In addition, good grounding measures can also discharge the charge accumulated on the shell due to electrostatic induction in time to avoid excessive voltage accumulation and high voltage when the electromagnetic pulse weapon attacks, resulting in damage to the internal discharge of the device.
In short, as long as appropriate measures are adopted, by adding filters, varistors and other components inside the electrical connectors of the aerospace electronic components; selecting suitable shell materials and plating on the outside; adopting special structural forms to ensure the electromagnetic of the connection gap Airtight: With the aid of proper grounding, the electromagnetic compatibility of the product can be greatly improved, and the anti-electromagnetic interference performance of the product can be increased. : Name: Lu Bin Gender: Male Date of Birth: 1973.11 Education: Postgraduate Work Unit: Hangzhou Aerospace Electronic Technology Co., Ltd. Title: Project Manager Title: Engineer Expertise: Component Design
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