orientation. A simple straight wire antenna will have one polarization when
mounted vertically and a different polarization when mounted
horizontally. A linear polarized antenna radiates wholly in one plain
containing the direction of propagation of the radio wave while, in a circular
polarized antenna, the plane of polarization rotates in a circle making one
complete revolution during one period of the wave. A linear polarized
antenna may be either Horizontally Polarized (if the direction of
propagation is parallel to the earth’s surface) or Vertically Polarized (if the
direction of propagation is perpendicular to the earth’s surface). A circular
polarized antenna may be either
Right-Hand-Circular (RHC) or Left-Hand-Circular (LHC) depending on
whether the direction of rotation of the plane of propagation is clockwise
or counterclockwise respectively. Polarization is an important design
consideration, particularly in Line of Sight (LOS) or Point-to-Point type
deployments because maximum signal strength between sending and
receiving antennas occurs when both are using identical polarization.
Radiation Pattern
of an antenna is a plot of the relative strength of the
electromagnetic field of the radio waves emitted by the antenna at
different angles. The radiation pattern of the theoretical isotropic antenna,
which radiates equally in all directions, would look like a sphere.
Impedance Matching
is an important consideration in the design of the
overall wireless communication system. At each interface, depending on
the impedance mismatch, some fraction of the propagating radio wave’s
energy will reflect back into the source. This reflecting wave is called a
standing wave and the ratio of maximum power to minimum power in the
standing wave is called the Voltage Standing Wave Ratio (VSWR). A VSWR
of 1:1 is ideal.
Types of Xirrus Antennas
The tables starting on the next page detail the specifications of the
different antennas Xirrus offers for use with its Access Points, in both
2.4GHz and 5GHz. Each type of antenna will offer certain coverage
capabilities suited for specific applications (as discussed in the later section
of this document). As a general rule of thumb as the gain of an antenna
increases, there is some tradeoff to its coverage area. High gain antennas
will typically offer longer coverage distance but smaller (and more directed)
coverage area.
* Each antenna can be connected simultaneously to 2 radios on different bands (2.4GHz and 5GHz) with additional cables. Additional antennas and cables
are required to connect multiple radios on the same band.
Antenna and Cables (Per Radio)
Antennas
XR-520H
ANT-CAB-195-10-MM
XR-2425H
ANT-CAB-195-10-MM
XH2-120
ANT-CAB-195-10-MM-02
15 degree 2.4GHz
(ANT-DIR15-2X2-2.4G-01)
1 A 2 cables
1 A 2 cables
1 A 2 cables
15 degree 5GHz
(ANT-DIR15-2X2-5.0G-01)
1 A 2 cables
1 A 2 cables
1 A 2 cables
30 degree Dual Band*
(ANT-DIR30-2X2-01)
1 A 2 cables
1 A 2 cables
1 A 2 cables
60 degree Dual Band*
(ANT-DIR60-2X2-01)
1 A 2 cables
1 A 2 cables
1 A 2 cables
90 degree Dual Band
(ANT-DIR90-2X2-01)
1 A 2 cables
1 A 2 cables
1 A 2 cables
Rubber Duck Dual Band
(ANT-OMNI-1x1-02)
2 Antennas, Direct attach
2 Antennas, Direct attach
N/A
Rubber Duck Dual Band
(ANT-OMNI-1x1-03)
N/A
N/A
2 Antennas, Direct attach
OMNI Antenna Dual Band*
(ANT-OMNI-2x2-02)
1 Antennas Direct attach
1 Antenna, Direct attach
N/A
OMNI Antenna Dual Band*
(ANT-OMNI-2x2-03)
N/A
N/A
1 A 2 cables
