NAL Research Corporation (TN2012-02-V1.0)
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EXT_ON_OFF line turns the A3LA-RS on and a logic low turns it off. Logic high is defined as having a voltage
ranging from 2.0V to 5.5V—do not allow logic high to exceed 6V. Logic low can range from
0.3V to 0.8V.
The current drawn on the external load used to pull the A3LA-RS to GND is no more than 20
A. The A3LA-
RS will draw approximately 20mA even in off state. Thus, DC power must be removed to eliminate any
parasitic current drawn. Damage may be caused to the A3LA-RS if EXT_ON_OFF is high and DC power is not
present. Users must ensure that this condition does not occur.
3.5 Typical Power Usage Profile
This section provides the electrical power profile of the A3LA-RS. It does not describe every situation;
however, it does offer a starting point for users to continue their own development design. The actual usage
profile can vary for a number of reasons. Users are reminded to optimize their setup to attain the lowest
possible power consumption. Some of the setup parameters to be carefully observed include:
1.
Have a clear view of the sky for the antenna—poor visibility of the sky is when a clear line-of-sight
is not available between the A3LA-RS and the satellites.
2.
Keep the antenna’s VSWR low—the higher the antenna VSWR the higher the current consumed by
the A3LA-RS.
3.
Keep the antenna cables’ loss to less than 3dB—the higher the antenna cable loss the higher the
current consumed by the A3LA-RS.
4.
Keep the power cable between the A3LA-RS and the power source as short as possible.
Power consumption of the A3LA-RS can be divided into four distinct operating segments: (1) standby,
(2) data-switch/RUDICS call, (3) SBD transmission, and (4) SMS transmission. Typical current drawn for
these cases are shown in plots below.
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Voltage (DC)
0.00
0.05
0.10
0.15
0.20
C
u
rr
e
n
t
(A
)
Figure 2.
Average current drawn during standby.