Abstract There are two commonly used methods for approximating the attenuation of shielding barriers. This approximation is defined as shielding effectiveness (SE) for shielding materials used in the design of shielded enclosures. Both methods use wave theory and quasi-stationary assumptions. One of the methods uses Maxwell’s equations to estimate the shielding, and the other … [Read more...]
Wireless Network Interference and Optimization
Introduction With the proliferation of embedded wireless systems in all imaginable products, comes the risk of increasing interference and resulting slowdown in data transfer. As we transition to a more mobile and connected society, the number of Wi-Fi (home appliances and control) and Bluetooth-enabled devices (speakers, headset, watches, etc.) is rapidly increasing. Add … [Read more...]
How to Choose Particle-Filled Silicones to Meet Multiple Design Requirements
Many electronic designs need shielding materials that combine resistance to electromagnetic interference (EMI) with other application-specific requirements. For example, the EMI gaskets that are used in military touchscreens need to attenuate EMI emissions, provide electrical conductivity, and ensure environmental sealing. These shielding gaskets also must also cushion the unit … [Read more...]
Does Your Automotive Printed Circuit Board Have Too Many Grounds?
Abstract One of the most widespread design defects in automotive printed circuit boards is the lack of an established high-frequency reference ground. This problem is exacerbated by a tendency among automotive design engineers to cut up solid current return planes in an attempt to establish “noisy” and “quiet” grounds. Introduction Too often, the designers of automotive … [Read more...]
The Future of Shielding
THE FUTURE OF SHIELDING The future is not all that far off. With more electronic devices that are getting smaller, more portable and with continuing faster speeds, EMI or RF issues will continue to increase. There will be more integrated system-onchips (SoCs) where several functions will all be in one device that will need to be electromagnetically isolated. As an example, a … [Read more...]
Introduction to MIL-STD-461G
Where MIL-STD-464C serves as a system/platform level set of requirements, MIL-STD-461G serves as an equipment/subsystem level set of requirements. Similar to MIL-STD-464C, MIL-STD-461G was developed as an “Interface Standard” to allow usage without a waiver. The overall structure of the two documents is also the same in that both have a contractual main body and a very … [Read more...]
Introduction to MIL-STD-464C
Responding to increasing criticism, Secretary of Defense William Perry issued a memorandum in 1994 that effectively eliminated the use of most defense standards. This has become known as the “Perry memo”. Many defense standards were canceled. In their place, the DOD encouraged the use of industry standards for quality assurance. MIL-STD-464 was developed as an “Interface … [Read more...]
Using An Oscilloscope To Verify EMC Tests For Automotive Electronics
Consumer demand for more entertainment, safety, and communication options within automobiles has significantly increased both the density of electronic components and the number of on-board wired and wireless signals. The result: an ever-expanding range of signals contained within the same car-sized fixed space. USING AN OSCILLOSCOPE TO VERIFY EMC TESTS FOR AUTOMOTIVE … [Read more...]
Basic EMC Concepts
Introduction Understanding EMC is all about two important concepts: (1) all currents flow in loops and (2) high frequency signals are propagated as electromagnetic waves in transmission lines. Currents Flow in Loops These two concepts are closely related and coupled to one another. The problem we circuit designers miss is defining the return path back to the source. If you … [Read more...]
Techniques For Mitigating Intrapair Skew-Induced EMI With Shielded Connectors
Introduction EMI stands for electromagnetic interference. There are several methods of EMI transmission from the source to the victim. Two of them are radiated EMI and conducted EMI. Radiated EMI happens when an electrical device produces an RF signal that is picked up and causes unwanted effects. Conducted EMI is unintentional energy carried out of the source via signal … [Read more...]
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