Abstract
The electromagnetic energy source used by wireless communication devices in a vehicle can cause electromagnetic compatibility problems with the electrical and electronic equipment on board. This work is focused on the radiated susceptibility (electromagnetic susceptibility [EMS]) issue and proposes a method for quantifying the electromagnetic influence of wireless radio frequency (RF) transmitters on board vehicles. The key to the analysis is the evaluation of the relation between the electrical field emitted by a typical Bluetooth device operating close to the automobile’s electrical and electronic systems and the field level specified by the electromagnetic compatibility (EMC) directive 2004/104/EC for radiated susceptibility tests. The chapter includes the model of a closed circuit structure emulating an automobile electric wire system and the simulation of its behaviour under electromagnetic fields’ action. According to this a physical structure is designed and implemented, which is used for laboratory tests. Finally, simulated and experimental results are compared and the conclusions obtained are discussed.
Key Terms in this Chapter
RF: Short for radio frequency, any frequency within the electromagnetic spectrum associated with radio wave propagation. When a RF current is supplied to an antenna, an electromagnetic field is created that then is able to propagate through space. Many wireless technologies are based on RF field propagation, including cordless phones, radar, ham radio, GPS, and radio and television broadcasts. RF waves propagate at the speed of light, or 186,000 miles per second (300,000 km/s). Their frequencies however are slower than those of visible light, making RF waves invisible to the human eye.
Bluetooth (Class I, II, and III): Bluetooth is the name of a wireless technology standard for connecting devices, set to replace cables. It uses radio frequencies in the 2.45 GHz range to transmit information over short distances of generally 33 feet (10 meters) or less. By embedding a Bluetooth chip and receiver into products, cables that would normally carry the signal can be eliminated. There are currently three flavours or classifications of Bluetooth devices, relative to transmitting range. As the range is increased the signal used in the respective classification is also stronger. Note that class III devices are comparatively rare.
CISPR: The Special International Committee on Radio Interference(abbreviated CISPR from the French name of the organization, Comitéinternational spécial des perturbations radioélectriques) is concerned withdeveloping norms for detecting, measuring and comparing electromagneticinterference in electric devices. CISPR’s principal task is at the higherend of the frequency range, from 9 kHz upwards, repairing standards thatoffer protection of radio reception from interference sources such aselectrical appliances of all types, the electricity supply system,industrial, scientific and electromedical RF, broadcasting receivers (soundand TV) and, increasingly, information technology equipment (ITE).
WLAN: The acronym for wireless local-area network. Also referred to as LAWN. A type of local-area network that uses high-frequency radio waves rather than wires to communicate between nodes. LAN is a computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN).
Anechoic (Semianechoic) Chamber: An anechoic chamber is a room in which there are no echoes. This description was originally used in the context of acoustic (sound) echoes caused by reflections from the internal surfaces of the room but more recently the same description has been adopted for the radio frequency (RF) anechoic chamber. A RF anechoic chamber is designed to suppress the electromagnetic wave analogy of echoes: reflected electromagnetic waves, again from the internal surfaces. Both types of chamber are usually built, not only with echo suppression features, but also with effective isolation from the acoustic or RF noise present in the external environment. In a well designed acoustic or RF anechoic chamber the equipment under test will only receive signals (whether acoustic or RF) which are emitted directly from the signal source, and not reflected from another part of the chamber.The semianechoic chamber is a shielded room with radio frequency absorbing material on the walls and ceiling (not on the ground). This semianechoic chamber simulates an open field test site, and eliminates any ambient signals that may be present in an open field environment.
Near Field Communication (NFC): A short-range wireless connectivity standard (Ecma-340, ISO/IEC 18092) that uses magnetic field induction to enable communication between devices when they are touched together, or brought within a few centimetres of each other. Jointly developed by Philips and Sony, the standard specifies a way for the devices to establish a peer-to-peer (P2P) network to exchange data. After the P2P network has been configured, another wireless communication technology, such as Bluetooth or Wi-Fi, can be used for longer range communication or for transferring larger amounts of data.
EMC-EMI-EMS: EMC is an abbreviation for electromagnetic compatibility. This means interoperability, or an electronic device’s ability to operate in an electric environment without interfering other electronic devices (emission), and without being interfered by other devices in its vicinity (immunity).EMC is divided into two main areas: electromagnetic interference (EMI) and electromagnetic susceptibility (EMS). These two areas are again divided into two categories of phenomena: conducted phenomena and radiated phenomena. EMC testing comprises measurements of the emission generated on in- and outgoing cables, the emission generated as electric fields surrounding the device, immunity against several disturbance phenomena on in- and outgoing cables, immunity against electric fields generated by other electronic devices and radio transmitters, and immunity against electrostatic discharges generated by human intervention.