Crossbow Technology MIB300, Руководство пользователя

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MPR/MIB User’s Manual
Wireless Sensor Networks
Doc. # 7430-0021-06 Rev. A Page 27
1024 _ Counts ADC V V
batt RSSI
× =
2 . 49 3 . 51 ) (
− × − =
RSSI
V dBm RSSI
for 433 and 315 MHz Motes
5 . 45 0 . 50 ) (
− × − =
RSSI
V dBm RSSI
for 915 MHz Motes
Figure 7-2. Graph showing V
RSSI
versus the received signal strength indicator (dBm). From the
ChipCon’s SmartRF
®
CC1000 PRELIMINARY Datasheet (rev. 2.1), p. 30. 2002.
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. An omni directional antenna such as a
quarter wavelength whip should be sufficient to meet most user requirements.
M
WARNING: The radio on the MICA2 has an extremely sensitive receiver, which can be interfered with
by an adjacent local oscillator from another MICA2. A distance of at least 2 feet should be maintained
between MICA2 units to avoid local oscillator interference.
7.2 MICAz
7.2.1 Radio RF Channel Selection
The MICAz’s CC2420 radio can be tuned from 2.048 GHz to 3.072 GHz which includes the
global ISM band at 2.4 GHz. IEEE 802.15.4 channels are numbered from 11 (2.405 GHz) to 26
(2.480 GHz) each separated by 5 MHz. The channel can be selected at run-time with the TOS
CC2420Radio library call
CC2420Control . TunePreset(uint8_t chnl)
. By default
channel 11 (2480 MHz) is selected.
7.2.2 Radio Transmission Power
RF transmission power is programmable from 0 dBm (1 mW) to –25dBm. Lower transmission
power can be advantageous by reducing interference and dropping radio power consumption
from 17.5 mA at full power to 8.5 mA at lowest power. RF transmit power is controlled using
the TOS
CC2420Radio library call
CC2420Control . SetRFPower(uint8_t power)
where
power
is an 8-bit code selected from the following: