If the frequency of the digital logic circuit reaches or exceeds 45MHZ~50MHZ, and the circuit working above this frequency has accounted for a certain amount of the entire electronic system (for example, 1/3), it is usually called a high-frequency circuit (multilayer circuit). plate). High frequency circuit board design is a very complex design process, and its wiring is critical to the entire design!

　　The first trick, high multi-layer circuit board wiring

　　High-frequency circuits often have high integration and high wiring density. The use of multi-layer circuit boards is not only necessary for wiring, but also an effective means to reduce interference. In the PCB Layout stage, the size of the printed circuit board with a certain number of layers is reasonably selected, and the intermediate layer can be fully used to set the shielding, so as to better realize the nearest grounding, and effectively reduce the parasitic inductance and shorten the transmission length of the signal, and at the same time, the large Amplitude reduction of signal cross-interference, etc., all of these methods are beneficial to the reliability of high-frequency circuits. Some data show that the noise of the four-layer board (multi-layer circuit board) is 20dB lower than that of the double-sided board when the same material is used. However, at the same time, there is also a problem. The higher the half-layer number of the circuit board, the more complicated the manufacturing process and the higher the unit cost. This requires us to select the appropriate number of layers of circuit boards when conducting PCB Layout. Reasonable component layout planning, and use the correct wiring rules to complete the design.

　　The second measure, the less lead bending between the pins of high-speed electronic devices, the better

　　The leads of the high-frequency circuit wiring are preferably all straight lines, and they need to be turned. They can be turned with 45-degree broken lines or arcs. This requirement is only used to improve the fixing strength of the copper foil in the low-frequency circuit, while in the high-frequency circuit, this requirement is met. A requirement can reduce the external emission and mutual coupling of high-frequency signals.

　　The third measure, the less the alternation between the lead layers between the pins of the high-frequency circuit device, the better

　　The so-called "the interlayer alternation of the leads is as few as possible" means that the fewer vias (Via) used in the component connection process, the better. According to the side, a PCB via can bring about 0.5pF of distributed capacitance, and reducing the number of vias can significantly improve the speed and reduce the possibility of data errors.

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