Andy Degraeve

Study on the reduction of heatsink radiation by combining grounding pins and absorbing materials

This paper describes a study on the effectiveness of grounding pins and high-frequency absorbers to reduce the emissions of heatsinks up to 20 GHz. The study considers four different types of excitations, namely a direct excitation, an excitation by a patch antenna, an excitation by a microstrip below the center of the heatsink, and an excitation by a microstrip that was off-set with respect to the center of the heatsink. Grounding post are positioned equidistantly along the edges of the heatsink and the number of grounding pins per side is varied. Adding grounding pins significantly reduces the emission of the heatsink below 1-2 GHz. At higher frequencies, they lose their capability to reduce the heatsink emission and even introduce extra resonance frequencies where the emission is higher compared to the ungrounded heatsink. Three different possible arrangements for the application of absorbing material were considered, namely a thin flat absorber just below the heatsink, a ring absorber between the heatsink and the PCB, and a collar absorber around the heatsink. The absorber succeeds in reducing the heatsinks emission above 1-2 GHz, but has little of no positive effect on the emissions below 1-2 GHz. Only by the combination of the grounding pins and the absorber material, a reduction of the heatsinks emission is achieved over the full frequency range.

Study of the effectiveness of spatially EM-diverse redundant systems under reverberation room conditions

In the most recent IET Guide on ElectroMagnetic Compatibiliy (EMC) for Functional Safety [1], diverse redundancy is indicated as one of the techniques to cope with the effects ElectroMagnetic (EM) disturbances within safety-or mission-critical applications. Unfortunately, up to now, little or no research is available on how to implement such EM-diverse redundant system. This paper studies the effectiveness of spatial diversity to cope with EM disturbances caused by strong incident fields under reverberation room conditions. Here, reverberation room conditions refers to the situation where multiple plane waves are incident onto the system-under-study, each with a random angle-of-incidence, polarization and phase. Four different geometries are compared: a non-redundant system comprising a single trace on a PCB, a redundant system comprising three parallel traces on a single PCB, a redundant system comprising three non-parallel traces on a single PCB, and a redundant system comprising three differently oriented PCBs. A reciprocity-based technique is used to efficiently calculate the induced voltages and the resulting bit error probability in the different geometries. It is shown that only when using three differently oriented PCBs a significant reduction in the bit error probability is obtained.

Study of the effectiveness of spatially EM-diverse redundant systems under plane-wave illumination

A typical technique within the area of Functional Safety to increase the Safety-Integrity-Level of a safety-critical system is the use of redundancy. However, failures due to Electro-Magnetic disturbances have to be regarded as systematic common-cause failures. When an Electro-Magnetic disturbance is incident on a redundant system with identical paths/hardware, these paths will very likely react in the same way. As a result, no benefit is obtained from the redundant system. To cope with Electro-Magnetic disturbances, Electro-Magnetically diverse redundant systems are needed. This paper studies the effectiveness of spatial diversity to cope with interference caused by strong incident plane waves. Four different geometries are compared: a non-redundant system comprising a single trace on a PCB, a redundant system comprising three parallel traces on a single PCB, a redundant system comprising three non-parallel traces on a single PCB, and a redundant system comprising three differently oriented PCBs. A reciprocity-based technique is used to efficiently calculate the induced voltages and the resulting bit error probability in the different geometries. It is shown that only when using three differently oriented PCBs a significant reduction in the bit error probability is obtained.

Shielding Effectiveness of anisotropic materials: How to measure?

In a number of applications, due to concerns such as weight and flexibility, shielding materials are used with anisotropic materials. Typically, in the case of some conductive textile materials, conductive yarns are only used in one direction (warp). Other materials will have different conductivity as a function of the direction, such as deployed metal grids. In this paper, measured Shielding Effectiveness SE results obtained by using different measuring setups are compared and discussed.

EMI Risk Management: A necessity for safe and reliable electronic systems!

Everyone has already been confronted with Electro-Magnetic Interference (EMI), ranging from an annoying buzz in a stereo when receiving a phone call to a computer crashing during a lightning storm. Frustrating, but not life threatening. However, two trends warrant appropriate concern: (ii) high-tech electronics is being used more and more for safety-related functions, (ii) electronic devices are increasingly vulnerable to EMI because of a lower intrinsic immunity and an increasingly severe electromagnetic environment. Combined expertise in Electro-Magnetic Compatibility (EMC) and Functional Safety (FS) will gain huge importance in many sectors like automotive, robotics medical, railways, avionics,... Unfortunately, EMC and FS have evolved separately and share no concepts nor terminology. EMI Risk Management must go well beyond the current state-of-the-art in classical EMC engineering. This paper describes the latest evolutions in the engineering discipline of EMI Risk Management.