It is Electromagnetic Compatibility that tracks the generation of radiated and conducted Electromagnetic Interference from the electrical circuit. Noise generation, poor EMI/EMC and poor signal transmission can result in electronic circuit failure. And it has been found that almost 50% of electronic circuit failure occurs due to EMI.
EM Compatibility is the ability of an electronic system to peacefully operate in an electromagnetic environment that too without producing any interference. An electrical device that consists of PCBs, ICs and I/O cables is more bound to generate electromagnetic interference. Generally, it is an IC that acts as a source, and PCB acts as a radiating antenna. Thus, it is crucial to measure the EM compatibility of the circuit.
Sources of EMI
Electromagnetic emissions are of two types – conducted and radiated EMI. Conducted EMI propagates via a power or signal bus and radiated EMI propagates from source that can be IC or location where EMI is produced. A receptor captures the electromagnetic wave that propagates from the edge of the printed circuit board. The receptor can be close-lying electrical equipment that is severely affected by the interference.
Further, electromagnetic emissions can also arise from traces of high-frequency that are routed close proximity with the PCB’s edge. Also, they can arise due to decoupling practices from power and ground.
Techniques to Reduce EMI/EMC Problems
Now, let us learn helpful techniques to reduce EMI/EMC problems.
- Line/Trace Spacing
To avoid EMI propagation, it is suggested to bend PCB traces at an angle of 45 degrees on their edges. Also, it is recommended to avoid microstrips. Other design practices that you should include are avoiding routing for signals of high speed over the slots and avoiding layer changes.
- EMI Shielding
EMI shielding prevents signal transmission and information loss. The primary purpose of EMI shielding is to reduce the effect of EMI and RFI on the electrical circuits. To shield a device, a metallic screen is added for absorbing the electromagnetic interference.
- Controlled impedance for transmission line design
It is crucial to design a printed circuit board with the right line impedance that matches the impedance of source to suppress EMI/EMC. Moreover, controlled impedance contributes to deciding fall and rise times of the signal. Impedance depends on the PCB material used on the board.
- Avoid antennas
It is suggested to avoid antennas as much as possible. Pay extra attention to unconnected stubs and traces without return paths.
- Separate sensitive components
To keep oscillator circuits away from other components, it is recommended to assign different PCB areas for different circuits. Also, keep high-speed components separated from disturbing signals and I/O connections
This article is sponsored by 3G Shielding who specialises in PCB and EMI shielding and has experience of more than 25 years. Many electronic companies rely on 3G to deliver leading-edge solutions for shielding advanced electronic applications. Experts of 3g Shielding work with their clients dedicatedly and bring the best solutions for unique RF/EMI/EMC challenges.
