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will improve on TTFF depends on the accuracy of position and time from a near base
station (service center) as well as hardware synchronization.
The AGPS function of the module is activated by sending u-blox binary protocol
UBX-AID-REQ. If there is no data available from a near base station, the module is
back to its normal start-up modes.
4.4 Sensitivity
There are three modes available for the module, which are “Normal”, “Fast
Acquisition” and “High Sensitivity”. Table 4.2 lists their associated definitions.
Sensitivity Modes Properties Notes
Normal Default setting
Fast Acquisition “Normal” sensitivity – 3 dB When the C/N
0
ratio of the
strongest GPS signal is
greater than 48 dB, this
mode can be used.
High Sensitivity “Normal” sensitivity + 3 dB When the C/N
0
ratio of the
strongest GPS signal is less
than 45 dB, this mode can
be used.
Table 4.2 Available sensitivity modes.
When the module tracks the weak GPS signals, the “High Sensitivity” mode is
preferable as compared with the case for tracking strong GPS signals in which the
“Fast Acquisition” is preferable. Different modes correspond to different TTFF times
under different start-up modes, i.e., it’s a trade-off between sensitivity and TTFF time.
Usually, the TTFF relationships among three modes are
TTFF
fast
< TTFF
normal
< TTFF
high
where
TTFF
( )
: TTFF for “Fast Acquisition”, “Normal”, or “High Sensitivity” mode.
Users are recommended to use the default setting, “Normal” mode, due to the
unknown and variable operating condition that the module is surrounded. The
sensitivity setting is activated by sending the request the UBX-CFG-RXM message.
NOTE: This module has a built-in LNA. If an active antenna with gain exceeded 25