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With the development of electronic communication technology, the application of wireless radio frequency circuit technology is becoming increasingly widespread. The functional objectives of the radio frequency circuit directly affect the quality of the entire product. The anti-interference planning of the radio frequency PCB circuit board has important implications for reducing the electromagnetic information radiation of the system. The density of RF circuit boards is increasing, and the quality of RF PCB printed circuit board planning has a significant impact on interference. The functional objectives of different RF PCB printed circuit board planning structures for the same circuit will vary greatly. If the assumption of electromagnetic interference signal is not properly handled, the whole circuit system may not work normally. Therefore, how to prevent and suppress electromagnetic interference and advance Electromagnetic compatibility has become a very important topic when planning RF circuit boards.
Electromagnetic compatibility EMC refers to the talent that electronic systems can operate normally in a regular electromagnetic environment according to the planning requirements. The electromagnetic interference suffered by electronic systems not only comes from the radiation of electric and magnetic fields, but also from the influence of common impedance of lines, coupling between wires, and circuit structure. When developing and planning circuits, it is hoped that the planned printed circuit board is as less susceptible to external interference as possible, and also as little interference as possible to affect other electronic systems.
The primary task of planning a PCB board is to analyze the circuit and confirm the key circuits. This is to identify which circuits are interference sources and which circuits are active circuits, and clarify how interference sources may interfere with active circuits. The frequency of RF circuit operation is high, and the interference source mainly interferes with the active circuit through electromagnetic radiation. Therefore, the purpose of RF circuit board anti-interference planning is to reduce the electromagnetic radiation of the PCB board and the crosstalk between the circuits on the PCB board.
1. RF circuit board planning
Layout of 1.1 yuan equipment
Due to the fact that SMT generally uses infrared furnace heating welding to achieve the welding of raw materials, the layout of raw materials affects the quality of solder joints, thereby affecting the product yield. As far as the RF circuit board planning is concerned, Electromagnetic compatibility requires that each circuit module should not produce electromagnetic radiation as far as possible, and have a certain ability to resist electromagnetic interference. Therefore, the layout of element equipment also affects the interference and anti-interference ability of the circuit itself, and directly affects the function of the planned circuit. Therefore, when planning RF circuit boards, in addition to considering the layout of general PCB planning, it is also necessary to consider how to reduce mutual interference between various parts of the RF circuit, how to reduce interference from the circuit itself to other circuits, and the anti-interference ability of the circuit itself.
Based on experience, the effectiveness of RF circuits not only depends on the functional objectives of the RF circuit board itself, but also largely on the mutual influence with the CPU processing board. Therefore, when planning RF circuit boards, reasonable layout is particularly important. The general principle of layout is that the components and equipment should be placed in the same direction as much as possible, and by selecting the direction in which the RF PCB circuit board enters the soldering system, the phenomenon of poor soldering can be reduced or even prevented; According to the experience, there must be a minimum interval of 0.5mm between the meta equipment to meet the soldering requirements of the meta equipment. If the PCB board
