By Kevin Chen, Connector Marketing, I-PEX
As high-speed Internet improves and the usage of large-capacity memory devices increases, high-resolution images and videos can be enjoyed more easily on consumer devices such as PCs, tablets and smartphones. The amount of information that needs to be processed on these devices has dramatically increased and the signal speed in these devices has been getting faster and faster.
EMI – electromagnetic interference – is a type of unwanted noise in an electrical net generated by an internal or external source. EMI can take various paths from the source to the affected device.
When EMI is generated from a device’s own internal digital timing signals or electronic components, this may cause failure of other parts within the same system. This is an intra-system EMC (electromagnetic compatibility) problem. It often causes headaches for engineers who must develop high-performance, hand-held or portable electronic devices, in which high-density electronic components are mounted. When connectors are used in these types of devices, EMI-shielded connectors are often required in order to prevent electromagnetic noise from becoming a problem.
Two common paths are radiated interference and conducted interference.
- Radiated Interference occurs when high-frequency signals traveling on a conductive surface, (or wire or PCB trace), generate a time-variant electromagnetic field. This electromagnetic field can be detected (radiates) some distance from that surface. The closer the distance between the source, and the adjacent surface (or wire or PCB trace), the larger will be the coupled field which can be detected. Since the adjacent surface is conductive, voltages and currents will be excited on it when in the presence of an electromagnetic field. Solutions for this normally require the use of shielded enclosures, cables, and connectors. If any one part of the system is unshielded, it will be a point of radiated EMI leakage.
- Conducted Interference occurs when intentional (or unintentional) signals in a circuit directly travel by conductor (e.g., wire or PCB trace) from one place to another, in such a way as to interfere with the proper operation of the destination circuit or device. Incoming power lines are one such example of conducted interference. In this case, use of line filters, capacitor networks and similar methods are employed to separate (or condition) the intended voltage signals from the interference voltages.
I-PEX has developed a high-performance EMC connector series using ZenShield® technology. This eliminates electromagnetic noise from the connector by including an appropriate grounding structure and cover, which includes the mounting position of the signal contact tails with metal shields. These connectors are widely adopted by customers to prevent EMI, especially in high-performance devices equipped with wireless communications functions, such as Wi-Fi, GPS, and LTE.
The 360-degree shielding design prevents electromagnetic noise radiation not only from the contact points of the plug and receptacle, but also from the board mounting part (SMT positions) of the signal terminals. In addition, both plug and receptacle shields are connected for grounding at multiple points when the connectors are mated, and are properly grounded to the board. This ensures enough ground return paths for the current generated in the metal shields of the connector. This works to suppress the emission of electromagnetic noise from the shield.
Keys to Connector Design for EMI Mitigation
- The entire connector is covered with 360° shielding, for both the plug and receptacle –– not only the contact part of the signal terminal, but also the board mounting part (SMT positions).
- The shield-to-shield interface between the plug and receptacle is effectively connected at multiple points.
- Furthermore, the connector shield-to-board interface is properly grounded at multiple points on the board, thereby improving the ground return path.
With these design features, the connector itself provides significant mitigation of EMI. ZenShield® gives designer engineers more flexibility for board design by allowing the connectors to be placed in close proximity to sensitive subsystems, such as transmit/receive antennas for wireless communications.
Find ZenShield® connectors at this link.
Download the ZenShield® whitepaper at this link.
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