Specifications

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3.8. GPS Receiver
The EM-X270 GPS function is implemented with the NAVMAN Jupiter32 module based
on the SiRF GSC3f chip-set. The GSC3f chip integrates baseband, RF sections and Flash
memory, thereby reducing power consumption and size. Integrated 4 Megabit flash
memory gives the user the ability to store configurations permanently.
The protocol supported is NMEA (National Marine Electronics Association) data
messages.
The Jupiter32 module is interfaced with the PXA270 processor via the STD_UART.
Antenna
The RF input is routed to a standard UFL connector for off-board antenna connection.
See section 4.12 for a detailed connector description.
The following table summarizes the recommendations for the EM-X270 GPS antenna:
Characteristic Passive Antenna Active Antenna
Polarization Right-hand circular polarized Right-hand circular polarized
Receive frequency L1 1.57542 GHz +/- 1.023 MHz 1.57542 GHz +/- 1.023 MHz
Power supply
-
3V
DC current
-
<10mA at 3V
Antenna gain 2 to 5 dBi with 1 dB loss (max)
in connections
-
Total gain - < 18dBi
Axial ratio: < 3 dB < 3 dB
Output VSWR
-
< 2.5
The active ceramic patch antenna available from Compulab (part name ANTGPS) meets
the requirements above and may be used for evaluation and pilot production.
Performance Specifications
The table below shows the corresponding TTFF times for each of the acquisition modes.
@ –125 dBm @ –140 dBm Mode
Typ 90% Typ 90%
Hot start TTFF 500 ms <1 s <1 s <1 s
Warm start TTFF 32 s 38 s 49 s 59 s
Cold start TTFF 34 s 42 s 52 s 66 s
Re-acquisition
(<10s obstruction)
1 s 1 s