EN
Electromagnetic interference (EMI) is a thorn in the flesh in the modern congested electronic world. With equipment racks overloaded with sensitive electronics, and spectrum becoming overloaded, an unwanted interference can be in the form of poor signal quality, data errors, or system failure. We know that EMI control at the RF level is not possible without a comprehensive approach and we have more than 20 years of RF experience at Linkworld. This guide discusses four fundamental measures of EMI reduction in complicated installations.
Selecting High-Shielding Connector Interfaces
The starting point of EMI control is at the connector interface. The shielding efficiency of a connector expressed in decibels of attenuation defines the capability of the connector to retain internal signal and eliminate alien signal. Critical applications require connectors that have continuous 360° shielding. Threaded connectors such as SMA, N-Type, and TNC provide better shielding than bayonet-type connectors because they maintain consistent contact pressure around the entire circumference. Special connectors use frequently more than 2 fingers of contact, or spring-loaded structures that maintain electrical contact under vibration or thermal cycling. Platings with high conductivity (silver, gold) reduce the surface resistance and enhance high-frequency shielding. The connectors of Linkworld have optimized shielding geometry, which offers the attenuation required in the most electrically noisy environments.
Optimizing Cable Assembly Construction
The cable is the longest continuous component of the signal path and a possible source of entry of electromagnetic energy. Compared to conventional single-shielded constructions, double or triple-shielded constructions are far better EMI protectors, utilizing several layers of braided and foil shielding. In the most challenging of applications, semi-flexible or conformable cables with solid copper outer conductors provide virtually ideal shielding. The quality of shield termination at the connector interface is also paramount--when a cable with perfect shielding is connected to a connector with a termination of poor quality, it leaves the connector vulnerable. The special cable assemblies produced by Linkworld use high quality shielded cable and accuracy of termination methods that preserve continuity of shielding at connector between connector and cable.
Implementing Proper Grounding and Bonding Strategies
Even the highest-quality shielded components will not suppress EMI when the grounding has not been done properly. The grounding of shields must be done at locations that offer a low-impedance path to any interference currents that may exist and without causing ground loops. In RF applications, this normally implies that the ground shields of both ends are grounded to ensure good high-frequency shielding, it is generally better than pigtail-terminated shields where ground inductances are concentrated to a point. The grounding studies can be required in complicated installations having two or more interconnected equipment to avoid the occurrence of ground loops. The engineering section of Linkworld offers technical advice on how the grounding should be done.
Managing Cable Routing and Separation
The physical layout in the equipment racks has a substantial effect on the EMI susceptibility. The old rule of non-mixing of signal and power cables is still valid: keep power cables and signal cables apart, keep high-level signals and low-level signals apart. Where cables have to cross, orthogonal routing (90-degree crossing) has minimum coupling compared with parallel runs. Different signal types do not mix in equipment racks since their cable types are segregated in special cable trays and pathways. In the most sensitive installations, the vulnerable circuits are physically segregated by compartments. Cables that are neatly bundled couple less with adjacent cables than. The custom cable assemblies produced by Linkworld can be done to have a specific length and connector orientation that allow proper cable routing.
To help minimize electromagnetic interference, it is necessary to follow a systematic plan and close all possible entry points. High shielding connectors, cable structure optimization, proper grounding and considerate physical layout are all combined to ensure signal integrity in the face of adverse electromagnetic conditions. Systems with increasing complexity and more frequency levels have an enhanced importance on EMI control. Linkworld has more than twenty years of RF manufacturing experience and of profound knowledge in interference control, and offers the components, custom assemblies, and technical advice to installations that are immune to EMI. Get in touch with us about your EMI control needs.