PCB News - Anti-interference design of high-speed digital PCB circuit board for train​

Source: Electronic Engineering World

1 Introduction

With the continuous development of science and technology, trains are also developing at a high speed, and high-speed digital circuits are gradually adopted in the train on-board system. There are many sources of interference on the train, including electromagnetic interference generated by various transformers, fans, pantographs, and air compressors, which affect the normal operation of high-speed digital circuits in the train. In addition, in order to ensure the comfort of the riding environment and working environment, the car is also equipped with various electrical equipment such as air conditioners, electric heaters, ventilators, etc. They also generate electromagnetic radiation to the outside, which affects the normal operation of high-speed digital circuits. Therefore, in such a complex environment on the train, how to ensure the reliability of high-speed digital signals will become particularly important. If these problems are not handled properly, it will lead to signal distortion, timing errors, system instability, and many other situations, which will bring inestimable losses.

In order to ensure the normal operation of train communication and control systems, the anti-interference design of the equipment is as important as the functional design. It is necessary to consider the suppression of digital circuit interference at the beginning of the design, otherwise it is difficult to meet the anti-interference requirements of high-speed digital circuits. Therefore, the anti-interference ability of the digital circuit board should be improved and the circuit radiation should be reduced first, and the anti-interference remedial measures of the circuit board should be avoided after the design is completed.

2 Interference formation method

Three basic ways of interference formation: interference source, coupling path, and sensitive source. The following describes these aspects respectively.

2.1 PCB circuit board interference coupling path

The interference on the PCB circuit board mainly includes common mode interference and differential mode interference. Differential mode interference is generated by the signal loop, and common mode interference is generated by the common mode current on the cable. For the printed circuit board, it mainly refers to its differential mode interference, because the frequency range of its differential mode interference is the entire frequency band occupied by the circuit signal. It can not only couple to the sensitive source devices through its wires, but also the current loop will also be coupled into the outside to produce All kinds of interference affect the normal working system. The main method to reduce differential mode interference is to minimize the length of the traces and reduce the signal loop area when wiring.

The above is an introduction to the anti-interference design of high-speed digital PCB circuit boards for P trains. Ipcb also provides PCB manufacturers and PCB manufacturing technology.