Report on: Measurement of Cellular Base-station Emissions Using a Newly Developed RF Field Mapping System*

Glossary

AMPS - Advanced Mobile Phone System, 1981. An FDMA system utilising frequency modulation with 30 kHz bandwidth per channel. This system is the one normally referred to as "analog cellular" and is the predominant FDMA technology used in Canada.

carrier - a radiofrequency signal consisting of a pure tone that is modulated with the information-carrying signal. Usually the radiofrequency signal is much higher in frequency that the information carrying signal.

dB - abbreviation for decibel, a unit that represents 10 times the logarithm (base-10) of a ratio.

DC - direct current. Current that flows in one direction only with respect to time. Also used loosely to describe the average value of a time-varying signal.

envelope - the excursions that the peaks of a modulated carrier, make in time. The envelope of the carrier traces out the power or power density of the signal with respect to time.

FDMA - Frequency Division Multiple Access. A cellular telephone system where the available bandwith is divided into a multitude of channels where each user occupies a separate channel.

GLOBE - Geographically Located Observations of Base-station Emissions. The acronym used for the instrument described in this report.

MEL - maximum exposure limit. The maximum exposure level allowed by a standard or guideline usually in terms of power density.

MHz - megahertz. An abbreviation for the unit of frequency in the SI system. One Hz is equal to 1 cycle per second. The prefixes k, M and G refer to one thousand times, one million times and one billion times, respectively. For instance, the frequency 1 GHz is equal to one billion cycles per second while 1 kHz is the same as one thousand cycles per second.

omni-directional - having receiving properties equal in all directions in the horizontal plane.

power density - the rate or amount of radiofrequency or electromagnetic energy flowing through a given area. It is measured in watts per square meter.

radiofrequency - the frequency in the portion of the electromagnetic spectrum that is commonly used to carry information over distances via radio waves. It typically encompasses the AM radio band (0.54 -1.7 MHz) to high microwave frequencies (100s of GHz) but may extend beyond these somewhat arbitrary limits.

SAR - specific absorption rate. The rate at which electromagnetic energy is absorbed in a mass of material divided by the mass. The material usually referred to in most discussions of SAR is living tissues; however the concept of SAR can be applied to any substance living or otherwise.

SAR is given in quantities of watts per kilogram, which are also the units used for metabolic rates in tissues. Since all the electromagnetic energy absorbed in tissues is converted to heat, SAR allows a direct comparison between electromagnetic energy absorption and metabolic output. Also, because of the way in which SAR is defined from the basic electromagnetic parameters, it can also be used as a measure of the internal electric field intensity in the tissues.

spectrum analyzer - an instrument used for measuring radiofrequency signal intensity and frequency. When used with a calibrated antenna, a spectrum analyzer is capable of measuring power density.

TDMA - Time Division Multiple Access. A cellular telephone system where the available bandwith is divided into a small number of channels where each user occupies a time slot in one of the channels.