APPENDIX G. GLOSSARY

TB 430133

APPENDIX G

GLOSSARY

Amplifier

An electronic device that increases the amplitude of the input signal without

changing its frequency.

Antenna

The system component that is used to radiate or receive electromagnetic

energy into/from space.

Antenna Array

A system of antennas coupled together to enhance the response of a single

antenna element.

Attenuation

A decrease in the intensity of any signal as it passes through an absorbing or

scattering medium.

Average Power

The timeaveraged rate of energy transmission. For pulsed emissions, the

product of the duty cycle and the peak power.

Averaging Time

The time period, often 6 minutes, which is used in assessing the potential for

overexposure when one is evaluating RF fields.

Balun Transformer

A device which provides coupling and matching between a balanced line and

an unbalanced (i.e. coaxial) line.

Band

The continuous range of frequencies extending between two specified

limiting frequencies.

Continuous Wave (CW)

A RF transmission in which the carrier is transmitted continuously, without

any breaks. Pertaining to a laser when irradiance is constant for periods in

excess of 0.25 seconds.

Controlled Area

An area where the occupancy and activity of those within are subject to

control and supervision for the purpose of protection from radiation hazards.

Cornea

The outermost structure of the eye that interfaces with the environment.

Diffuse Reflection

Takes place when different parts of a beam incident on a surface are

reflected over a wide range of angles.

Dipole Antenna

A horizontal antenna, typically linear in design, which has its length related to

the wavelength of the signal and where the signal is typically fed at its center.

Dummy Load

A dissipative device used at the end of a transmission line or waveguide to

convert RF energy into heat so that free space radiation is prevented.

Duty Cycle

The ratio of the system "on time" to "on + off time" or total exposure duration.

Electromagnetic Radiation

The propagation of varying electric and magnetic fields through space at

some velocity depending on the medium through which it is travelling.

Feed

The part of an antenna which couples RF energy to the antenna or reflector

from the transmission line.

Frequency

The number of cycles per second of a periodic oscillation.

Hazard Distance

The distance personnel should be from the transmission main "beam"

(optics) or field (RF antenna).

Hertz (Hz)

The unit of frequency or cycles per second. (see also frequency)

Horn Antenna

An antenna consisting of a waveguide section whose crosssectional area

increases toward the open end through which electromagnetic energy is

radiated or received.

Electromagnetic radiation with wavelengths which lie within the range 0.7 m

Infrared Radiation (IR)

to 1000 m. This region is often broken down into three spectral bands by

wavelength: IRA (.7 1.4 m), IRB (1.4 3.0 ), and IRC (3 m 1000

m).

Interlock

A device used to interrupt the operation of a potentially hazardous RF/ELF or

laser source.

G-1