As devices ranging from smartphones to medical devices to cars process ever-increasing amounts of data, signal speeds are increasing for all types of electronic devices.
Electromagnetic interference (EMI) is a type of unwanted noise in an electrical network that is generated internally or externally. EMI generated by a device’s own internal digital timing signals or electronic components can cause other components in the same system to malfunction. This is an intra-system electromagnetic compatibility (EMC) issue.
EMI can cause problems for design engineers developing high-performance electronic devices that are populated with high-density electronic components. When interconnects (or connectors) are used in these types of devices, these connectors often require EMI shielding to prevent electromagnetic noise from becoming a problem.
1) Radiated interference occurs when a high frequency signal propagating on the surface of a wire or PCB trace generates a time-varying electromagnetic field. This electromagnetic field radiates and can be detected at a distance from the surface. The shorter the distance between the source and the surface of the adjacent wire or PCB trace, the greater the coupled field that can be detected. Since the adjacent surface is conductive, the electromagnetic field induces voltage and current. Solutions in this area usually require shielded enclosures, cables, and connectors. If any part of the system is not shielded, it becomes a radiated EMI leakage point.
2) Conducted interference occurs when intentional or unintentional signals in a circuit propagate directly from one place to another through a conductor, thereby interfering with the normal operation of the target circuit or equipment. The input power line is an example of conducted interference. In this case, line filters, capacitor networks, and similar methods are used to separate the intended voltage signal from the interfering voltage.
- Three connector design features for effective EMI mitigation
1) The entire connector should have 360° shielding, including the plug and receptacle, the board mounting portion (SMT location), and the contact portion of the signal terminals.
2) The shield-to-shield interface between the plug and receptacle should be effectively connected at multiple points.
3) The connector shield-to-board interface should be properly grounded at multiple points on the board to improve the ground return path.
