Lecture
More than a century after electromagnetic radiation began to be used for the needs of humanity, these emissions keep finding new and new applications in various fields of industry, science and technology. Broadcasting, television, radio communication, radar, radio navigation, ship navigation, and radio control of aircraft and mobile vehicles − are the most widely known fields of application of electromagnetic waves. In addition, medicine, chemistry, geology, meteorology and many other fields of human activity are increasingly adopting the achievements of modern radio engineering and electronics for their own needs. The exploration of the World Ocean and outer space has also opened up new possibilities for radio electronics. The widespread deployment of radio-electronic equipment (REE) means that, when operating simultaneously, such equipment begins to affect one another. Therefore, when designing REE, it is necessary to take into account its operating conditions, including the electromagnetic environment in which the REE must work. The electromagnetic environment (EME) − is the totality of electromagnetic emissions at a point or in an area where REE is located (or is intended to be located). Electromagnetic emissions can degrade the quality of REE operation, up to a complete inability to perform its main function. The appearance of new REE changes the EME at points where operating equipment is already located. This change can degrade the operating quality of some of that equipment. Solving the problem of ensuring satisfactory operation of REE within the surrounding EME, without exerting an impermissible effect on it or other equipment, constitutes the essence of the electromagnetic compatibility (EMC) problem.
The scope of application of radio systems in various fields of human activity is constantly expanding: relatively new applications of electromagnetic oscillations have appeared in such fields as chemistry, geology and medicine. Satellite communication systems, subscriber radio access systems for telephone and information networks, and radio-frequency identification systems have become widespread, and new stationary and mobile radio communication technologies built on cellular structures have been introduced. Moreover, systems with a cellular spatial structure are distributed throughout the entire service area. In most cases, administrative or industrial buildings of increased height, which have a dominant position over the surrounding development, are chosen for installing base stations. As a result, a large number of diverse radio equipment items are installed at individual sites (antenna towers, building rooftops and other structures). At base stations, in addition to the main technological equipment, radio relay equipment of transport networks and other equipment is typically also installed. The number of radio-electronic equipment (REE) units performing VHF-FM broadcasting from various sites in urban and rural environments has noticeably increased.
The problem of efficient use of the radio-frequency spectrum (RFS) and of ensuring electromagnetic compatibility (EMC), i.e. conditions for the normal operation of REE without impermissible mutual interference, is becoming urgent and quite complex. Therefore, when developing modern REE, it is especially necessary to take into account its operating conditions, including the electromagnetic environment in which the REE must work. The emergence and increasing complexity of the REE EMC problem has been due to various causes, listed below:
Since the range of frequencies used is limited, the significant number and crowding of REE antennas installed at a single site, the increase in the level of interference, including interference radiated in undesired directions, as well as the increased susceptibility of radio systems to interference, contribute to a violation of EMC conditions. Moreover, interference can arise in REE and penetrate it at frequencies other than those of the operating band, thereby degrading its quality indicators.
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