Wireless Technology
Safe and sound
Most mobile communications equipment employs radio-frequency technology in some form, but there are certain situations where RF can be problematic. Steve Cranstone looks at the issues involved and how infra-red can provide a better alternative
R
adio-frequency technology is the basis of many types of equipment designed for mobile
communications, and in the majority of cases it provides a perfectly satisfactory solution. However, there are an increasing number of applications in which the use of RF can present a significant security risk, be subject to interference problems or even in the extreme case present a danger to life.
The potential problems with RF communications are due to the emissions from the equipment and also its susceptibility to interference from other sources of RF. Although the average power level of mobile communications equipment is generally low, the peak power radiated can cause significant problems in nearby electronic equipment. Sensitive electronic circuits may not necessarily be damaged by the induced voltages and currents, but they can temporarily generate extraneous output signals, which can disrupt control loops or cause unwanted shutdown of equipment. For this reason, many industrial companies have banned the use of radio equipment in control centres and computer rooms. In explosive environments such as oil terminals or military munitions stores, the consequences of such induced voltages are potentially much more serious and may even endanger life.
Another significant drawback of RF technology is the fact that it is possible to detect the signals and eavesdrop on what is being said, which could present a major risk in military and counter-terrorism operations. For example, so-called ‘secure’, ‘short range’ Bluetooth transmission can be detected and decoded at an order of magnitude greater distance than it is designed to operate.
Figure 1: The Azdec Infra-Com system employs digital encoding techniques for crystal-clear communications
18 December 2011/January 2012
A further issue is the possible adverse health effects of the electromagnetic fields generated by radio communications equipment. Indeed, concerns have been raised about emissions over the whole electromagnetic spectrum, from the low
Components in Electronics
frequencies used for electrical power transmission to the higher frequencies of mobile phones.
In addition to such potential problems with the emissions from mobile comms devices, there are also issues with their susceptibility to interference from nearby electrical equipment. Power electronics systems in particular – where large currents are switched at relatively high speeds using power transistors or GTO thyristors – can generate significant electromagnetic fields, which may cause
substantial degradation of radio communications.
Equipment that generates strong
electromagnetic fields can be found in a wide range of industrial and military locations, including ships, submarines, oil production platforms, steel manufacturing facilities, electricity substations, broadcast transmitters and many more. In the military sphere, the deliberate use of interference to disrupt radio
communications, or jamming, is of course a key element of electronic warfare.
Figure 2: The Azdec Infra-Com system is suitable for use in security-sensitive applications
www.cieonline.co.uk
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