PCB Designing Situations: A new customer discovered a radiated emissions problem involving a product at an advanced stage in the production cycle. They had results from another test lab that showed failure at two frequencies (with marginal results at others) and they needed some assistance in improving the EMC performance.
The electromagnetic compatibility (EMC) will monitor the generation of the radiated and conducted electromagnetic interference (EMI) from electronic circuitry.
Poor EMI/EMC, noise generation and poor signal transmission are found to be the key reasons for electronic circuitry failure.
The telecommunication sector is one of the key sectors that is driving demand for EMI free PCBs. Electromagnetic compatibility (EMC) is the ability of an electronic system to operate within an electromagnetic environment peacefully without generating an unintentional EMI (electromagnetic interference).
Understandably, EMC is treated as a property of the electronic circuit where the circuit radiates lesser EMI to its environment.
An electronic system that consists of printed circuit boards. Every printed circuit board (PCB) should be able to operate without disruption due to interference from other devices and without causing interference. To accomplish this, PCBs need to have strong electromagnetic compatibility (EMC) built-in from the ground up.
There are two electromagnetic emission types, such as conducted and radiated EMI. Conducted electromagnetic emission will propagate through the system via a power or signal bus.
While, the radiated EMI is an electromagnetic wave that propagates from the source – which can be an integrated chip or a location where electromagnetic interference is generated – the electromagnetic wave that is propagated from the edge of the PCB will be captured by a receptor. This receptor can be nearby equipment and will be affected severely by the interference.
How to design board with low or absolutely zero electromagnetic interference? Well, it isn’t impossible. All you need are world-class industry experts who will tell you the best design practices to follow for
neglecting EMI/EMC problems in your design. Following techniques can be used to reduce EMI/EMC problems while PCB designing:
- Line/Trace Spacing: To avoid EMI propagation, it is preferred that PCB traces should be bent at a
45-degree angle on their edges. It is also recommended to avoid microstrips and adopt
striplines. - Importance of Shielding: EMI/EMC shielding is carried out by adding a metallic screen for
absorbing the electromagnetic interference. - Importance of Grounding: Adoption of a large, unbroken ground reference plane, and
connecting it to the ground plane with the ground vias will reduce interference. Designers must
provide return paths for the ground plane. - Decoupling: The decoupling capacitors are used for faster switching between IC power and
ground connections, thus limiting the radio frequency emissions. - Separate Sensitive Components: ou need to assign different PCB areas for diverse circuits in
order to keep oscillator circuits away from other components. Additionally, high-speed
components must be separated away from disturbing signals and from I/O connections.
Questions On PCB Designing Issues
- What is EMI and EMC?
- What are effects of EMI on circuit performance?
- What are types of EMI?
- Is it possible to have design with zero EMI?
- Which techniques are used to reduce EMI problem in case of PCB Design?
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Excellent and useful article. You have given a nice idea and suggestion in this post. In the end we all need to satisfy our clients through our work. So thank you for the post and keep sharing.