Electromagnetic Compatibility Design Of WIFI6 Router

With the continuous improvement of the working frequency and integration level of modern electronic products,EMC has become a major issue that plagues electronic design.Routers are a microcosm of modern high-speed electronic devices,which contain radio frequency circuits,antennas,high-speed digital circuits,as well as floating metal,network cables,and power cords that can easily induce electromagnetic compatibility problems.The indicators of WIFI6 have greatly improved compared to WIFI5,and EMC issues also face new challenges.Adopting new design methods and ideas in the design phase to address potential EMC issues can ensure the first article success rate of electronic equipment,thereby reducing investment costs and shortening the research and development cycle.This article combines relevant theoretical knowledge to improve the EMC performance of WIFI6 routers from various aspects of the system.The main work and achievements are as follows:1.Analyze the typical noise sources generated by DC-DC and the noise coupling mechanism of the noise on the 5GHz RF front-end.Suppress the noise in the schematic design and PCB layout,and verify it using field circuit collaborative simulation.2.Introduce some basic high-speed PCB design criteria,and then use electromagnetic simulation software such as ANSYS and ADS to verify some parts of the PCB that may cause EMC risks during the design phase.3.Routers generally use the PCB ground plane as a part of the antenna to reduce the antenna size,such as a monopole antenna or an inverted F antenna.High speed digital circuits can generate large noise currents on the ground plane.Because both antennas rely on the reference plane,this noise current can easily be coupled to the antenna,resulting in radio frequency interference.To address these issues,this article designs a 2.4 GHz antenna that distributes most of the radiation current within the antenna itself.Due to the small current distribution in the ground plane,the antenna can achieve higher isolation and lower radio frequency interference.Then,by folding the area where the antenna current amplitude is small,the miniaturization design of the antenna is realized.4.Ethernet transformer is a key component of the network interface filter circuit,which integrates a center tap transformer and a common mode choke coil.Due to its large volume and the internal coil is generally manually wound,the consistency is poor.In this paper,discrete center tap transformers and common mode chokes are used,which can reduce the size of the network filter circuit and improve the consistency problem.Based on the analysis of the main noise modes of the network interface circuit,an optimized network interface filter topology is obtained,which can achieve better suppression of common mode current at the network interface.Through the aforementioned efforts,WIFI6 routers can comply with the radio frequency standards of the WIFI6 protocol,as well as pass the European standard EN55032 for electromagnetic compatibility requirements of information technology equipment,which is stipulated by the European Union.