User's Manual

MPR/MIB User’s Manual
Page 26 Doc. # 7430-0021-07 Rev. B
8 Antennas
8.1 Radio/Antenna Considerations
Care should be taken to provide an antenna that provides proper coverage for the environment
expected. Range and performance are strongly affected by choice of antenna and antenna
placement within the environment. In addition, care must be taken to ensure compliance with
FCC article 15 regulations for intentional radiators. Because of its small physical size, the usual
antenna chosen is a length of insulated wire one-quarter wavelength long for the frequency of
interest. This type of antenna is often called a monopole antenna, and its gain is ground plane
dependent.
Antenna lengths for the different radio frequencies are provided in
Table 8-1.
Table 8-1. Antenna lengths for quarter wavelength whip antennas. The part number’s for the
connectorized antennas are listed.
Name Model
Whip Antenna Length
(inches)
Crossbow Part
No.
MICA2/MICA2DOT MPR400 (916 MHz) 3.2 8060-0011-01
MICA2/MICA2DOT
MPR410 (433 MHz) 6.8
8060-0011-02
MICA2/MICA2DOT MPR420 (315 MHz) 9.4 8060-0011-03
MICAZ MPR2400 (2400 MHz) 1.2 8060-0011-04
Antennas are also available from Linx Technologies, such as part number ANT-433-PW-QW for
433 MHz and ANT-916-PW-QW for 916 MHz. These antennas are terminated in a coax pigtail,
and must have an MMCX connector installed. They also function best with a ground plane
installed, as shown in
Figure 8-2. The ground plane can be a layer of aluminum or copper tape
attached to the lid of a plastic enclosure, or the lid of a metal enclosure.
Figure 8-2. Illustration of an antenna option for the motes using a Linx antenna and ground
plane.
1/2 WAVELENGTH
RECOMMENDED
METALLIC
GROUND
PLANE
NUT MAKES
CONTACT WITH
GROUND PLANE
1/2 WAVELENGTH
RECOMMENDED
1/2 WAVELENGTH
RECOMMENDED
METALLIC
GROUND
PLANE
NUT MAKES
CONTACT WITH
GROUND PLANE