Most designers . and installers of electrical equipment agree that shielded cables are a good way to achieve EMC. But many times I have seen big money thrown ”down the drain” because of overconfidence to the cable shield effects and ignorance of its proper use and design.
The number of mobile . subscriptions in the world is now as large as the number of people. To ensure future market growth, the mobile industry is working towards a vision that will make today’s use of mobile communications look like a mere starter.
Robotic lawn movers, . small autonomous robots, are becoming more and more popular in the gardens. With a minimum effort the garden is kept tidy, without the noise and emissions from a petrol engine. But how about EMC-related emissions then? And will the lawn mower co-exist with other products?
An editor´s reflections . Sometimes EMC issues result in dilemmas where conflicting needs / requirements need to be addressed.
Preamble . As briefly described.in our introductory Article N°1 (Issue #2-2015 of EE Magazine), ElectroMagnetic Compatibility is both a functional neccessity – equipments must operate in their intended environment without being disturbed nor causing disturbances to other devices- and a society requirement: interfering with radio/TV broadcast, radio-communications and other RF services is illegal and punishable by laws. Since consumers cannot be easily prosecuted as guilty for using an equipment that is causing interference, the most efficient way of controlling this EMC situation is to apply stringent limits to manufacturers, such as the products they put on market will “never” (exceptional situations accounted) cause interference.
EYE ON . It is relatively easy to achieve good attenuation (> 80 – 100 dB) of electromagnetic fields using a compact metal shield. In most practical cases, the shield is not complete, there are almost always openings, i.e. slots, windows and apertures. It is mainly these imperfections in the shield that determines the overall shielding effectiveness of the box.
The new version . of the JAS39 Gripen fighter is now a strong competitor in the fighter aircraft world market and the aircraft operates in several countries. A historical review of the early EMC work for the Gripen project may be of interest. The JAS 39 Gripen fighter aircraft project was outlined and presented in 1979-1981 by SAAB Military Aircraft & The Industry Group JAS also including the Ericsson Microwave Co. and Volvo Flygmotor. The development of the Gripen system and a production of 30 aircraft for the Swedish Air Force was decided by the Government in 1982. The decision was made after an intense debate in the media whether Sweden had the competence and capability to continue the independent fighter aircraft development although such projects had become extremely complex and costly.
Tactical communications . for ground-based operations requires many co-located communication systems on combat vehicles. Typical frequency bands for such communications are the 30–88 MHz band for army combat radio and the harmonized NATO band 225–400 MHz. As a result of increasing demands of different communication services and larger bandwidth, the amount of co-located communication systems in these bands is continuously increasing. A consequence of this is that the used frequencies will be less separated, meaning that out-of-band properties will be of severe importance for the performance of the individual systems.
An editor’s reflections . The EMC area has evolved in different directions since it was born about hundred years ago. From the beginning, the driving force was concerns about unintentional interference from electronics and how such interference might affect the new public radio broadcasting services.
EYE ON . Shielding is one of the concepts associated with EMC. Often, for example, mechanical engineers are tasked to build a shielding box, without further specification of ie operating frequencies or desired attenuation.
How much attenuation is reasonable to expect?