There are few words in an electrical engineer’s life that make them cringe more than EMI (Electromagnetic Interference). From noise on the lines to crippling entire infrastructures, whether large or small, EMI presents a serious problem.
As all active electrical systems emit electrical noise, every device is susceptible to the damages of EMI. Since this dilemma is almost inescapable, how does one go about dealing with EMI, and why is it so important that your connectors/cables support passing the EMI compliance test?
Eliminating EMI Through Shielding
One of the most common approaches to dealing with this pesky foe is to use some type of shield in your connector/cable system. Contrary to popular belief, a board-to-board connector shield is not designed to shield the contacts from radiating noise. Instead, the shield minimizes the noise voltage between ground planes. These shields often take the form of ground pins surrounding the high speed pins. At high frequencies, ground connections are not electrical shorts, rather they can act as inductors. These can develop a small noise voltage across the boards, creating problems. Hence, shielding is necessary.
For cabled systems, requirements can be slightly different. Key elements of a shielded cable include cable braiding, separable interfaces, and circumferential mating to the chassis. The shielding performance of the cable is only as good as its weakest link. For this reason, it is crucial that all three of these methods are implemented correctly.
EMI and Samtec
In the connector/cable industry, many manufacturers may offer what is known as “psychological shielding.” Unfortunately, most of the time, this proves to be just what it sounds like — psychological. True, there may be a shiny piece of metal surrounding your connector, and yes that cable you have been eyeing up may have ferrite beads, but what are these really good for?
At Samtec, protection against EMI is important to us. Working both in-house at our Harrisburg Design Center and through various partners, Samtec tests its connectors and cables using methods such as:
- Raw cable shielding tests
- HFSS Shielding Performance
- TRP Simulation Models
- Shielding Room/Dual Reverb Chambers (see photo)
Several connectors/cables that have been tested include:
By utilizing these tools, we guarantee that when we say something is shielded, we mean it. A brief example of our shielding tests and results is illustrated in the video below. Additional resources are also listed to assist with your next run in with EMI when designing your system, please feel free to reach out.
- Signal Integrity Group (SIG)
- Teraspeed Consulting
- Optimize Bandwith With The Signal Integrity Group and Teraspeed