PathAlign-R
Spectracom Corporation
2200 / 2240 / 2241 PathAlign-R Manual
5-48
3. The
far-field
, or
Rayleigh distance
(historically called the Fraunhofer region), is that
region where the radiation pattern is independent of distance.
These distances, where D is >>
λ
, and r is >> than
λ
, can be summarized as follows:
Region:
Distance from antenna (r)
Near-field
0 to 0.62v(D3/
λ
)
Fresnel zone
0.62v(D3/ λ) to 2(D2/
λ
)
Far-field
2(D2/
λ
) to 8
Where:
D = The maximum dimension of the antenna;
r = The distance from the antenna (boundary radius); and,
λ
= Wavelength [5].
5.3.5 Polarization
The polarization of an antenna refers to the orientation of the electric field vector in the radiated
wave. For linear polarization (horizontal or vertical), the vector remains in one plane as the wave
propagates through space. To eliminate polarization mismatch loss, the receiving antenna must
have the same polarization orientation as the transmitting antenna [3] (
Note
: If the waveguide
connection at the antenna is vertically oriented, the antenna is said to have horizontal
polarization and vice-versa).
5.3.6 Order Wire
The term ‘Order Wire’, or ‘Engineering Order Wire’, is currently used with spread spectrum
radios to describe the ability to have voice communications over the radio link. This term comes
from the telegraph/telephone days when an ‘order wire’ was equipment and the circuit (specific
cable pair within multi-pair cable) providing a telephone company with the means to establish
voice contact between the central office and carrier repeater locations [4].
5.3.7 References
1. T. L. Frey, Jr., The Effects of the Atmosphere and Weather on the Performance of a mm-
Wave Communication Link, Applied
Microwave and Wireless Magazine, February, 1999, pg. 76-80.
2. R. L. Freeman, Telecommunication Transmission Handbook, Third Edition, John Wiley &
Sons Inc., 1991, pg. 494.
3. A. M. Alevy, Antenna Fundamentals for Microcellular Applications, Base Station/Earth Station
Magazine, January/February
1999, pg. 28, 33.
4. H. Newton, Newton’s Telecom Dictionary, Fourteenth Edition, Telecom Books, 1998.
5. W. L. Stutzman & G. A. Thiele, Antenna Theory and Design, Second Edition, John Wiley &
Sons Inc., 1997.
6. D. G. Fink, Standard Handbook for Electrical Engineers, Tenth Edition, McGraw-Hill, 1969.
Section 15-80.
7. D. G. Fink, Electronic Engineers Handbook, First Edition, McGraw-Hill, 1975.
Summary of Contents for Pendulum PathAlign-R 2200
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