In the context of today's increasingly popular 5G and IoT applications, the design and application of radio frequency circuits have become increasingly important. Radio frequency circuits are those that handle electromagnetic wavelengths that are comparable to the size of the circuit. Such circuits need to be treated using distributed parameter theory. Therefore, they have a wide range of frequency processing.
In the field of PCB design, the performance indicators of RF circuits directly determine the quality of the final product. Especially in miniaturized products, the dense layout of components causes electromagnetic interference problems to be particularly prominent. If electromagnetic interference is not effectively dealt with, it may cause the entire circuit system to fail to work properly. Therefore, in the PCB design of radio frequency circuits, improving electromagnetic compatibility and preventing and suppressing electromagnetic interference have become a key issue in the design.
Component layout
In RF circuit PCB design, the layout of components has a direct impact on the interference and anti-interference capabilities of the circuit, which in turn is related to the performance of the designed circuit. When designing RF circuit PCB, in addition to considering the elements of ordinary PCB design, special attention must be paid to how to reduce mutual interference between circuits, how to reduce the interference of the circuit itself on other circuits, and how to improve the anti-interference ability of the circuit itself.
Components should be laid out according to the principle of arranging in the same direction, and welding defects can be reduced by selecting the direction in which the PCB enters the tin melting system. At least 0.5mm spacing between components is required to meet the tin melting requirements. If the PCB board space allows, the spacing between components should be expanded as much as possible. In a double-sided design, one side is typically used for SMD and SMC components, while the other side houses discrete components.

wiring
During the wiring process, all lines should be kept as far away from the edge of the PCB as possible (about 2mm) to avoid the risk of wire breakage during the manufacturing process. The width of the power line should be appropriately increased to reduce loop resistance, and the layout of the power line and ground wire should be consistent with the direction of data transmission to enhance anti-interference capability. Signal lines should be as short as possible, reduce the number of vias, and minimize mutual electromagnetic interference. Incompatible signal lines should be kept away from each other and parallel wiring should be avoided as much as possible. Where corners are required, 135° angles should be used to avoid right angles.
The traces directly connected to the pads should not be too wide, and the traces should be kept away from unconnected components to prevent short circuits. Vias should not be drawn on components and should be as far away as possible to prevent false soldering, continuous soldering or short circuits during production.
Power and ground wiring
In RF circuit PCB design, the routing of power lines and ground lines is crucial. Reasonable wiring design is the key to overcoming electromagnetic interference. Many interference sources on PCB are generated through power supply and ground wires, among which the noise interference caused by ground wires is the most serious.
The main cause of ground wire interference is the impedance of the ground wire. When current flows through the ground wire, a voltage will be generated on the ground wire, forming a ground loop current, causing loop interference. When multiple circuits share a section of ground wire, common impedance coupling is formed and ground wire noise is generated. Therefore, the use of common ground wires should be avoided in the design to reduce ground wire interference.