Design

Surveys show that price and performance are still the most important consumer criteria when selecting a mobile device.¹ However, increasing commoditization coupled with growing environmental concerns are placing sustainability front and center among considerations for manufacturers that hope to differentiate their products and demonstrate good corporate stewardship.

Today’s electrical and electronic devices are subject to mandatory EMC requirements throughout the world. Many devices operate at high frequencies and are very small. They are placed in nonconductive plastic cases providing no shielding. Essentially, all these devices cannot meet these mandatory requirements or they may cause interference to other devices or receive interference causing susceptibility problems without a proper program of EMI control. This program consists of identifying the “suspect” components and circuits that may cause or be susceptible to EMI. This is completed early on in the program to allow for an efficient design in keeping the cost of dealing with EMI as low as possible. A complete EMC program consists of proper filtering, grounding and shielding. This article will discuss the latter, but the other factors cannot and will not be ignored or given insufficient priority.

Many manufacturers design a product first, then attempt to “fix” the design later to meet the applicable safety standard. Prior knowledge of the applicable safety standard and its requirements for the product will help meet deadlines, keep design costs down, and result in a properly designed product.

Automobiles typically have dozens of electronic systems operating interactively in a relatively compact space. These systems must operate reliably in a wide range of environments over extended periods of time. As a growing number of these systems play an ever expanding role in protecting the safety of a vehicle’s occupants, there is an increasing need to ensure that the integrity of these systems will not be compromised by electromagnetic interference.

Considering EMC techniques during the design phase will minimize EMC problems and avoid disasters uncovered at EMC test time. At this time, the remedial measures are usually very painful.

In the typical case, where the electronic equipment is contained within a single enclosure, enclosure shielding along with cable filtering or shielding are commonly employed to meet EMC requirements.

This article deals with improving EMC measuring methods that are used during the development of automobiles in the field of interference emissions. Development-stage investigations are normally performed with measuring systems that have actually been conceived for vehicle component tests. EMC measuring methods that are tailored to the development stage, however, are much better suited for this task since they help save time and costs. One such measuring method is presented here as a practical example.