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Figure 3:
2.2.5
Antenna input
The module supports passive and active antennas. The antenna input RF_IN impedance is 50 ohms
and it provides also a bias supply low-pass filtered form VDD_ANT supply. The RF input signal path
contains first a SAW band-pass filter, which provides good out-of-band protection against GPS blocking
caused by possible near-by wireless transmitters.
Note that antenna input is ESD sensitive. With passive antennas the ESD performance can be
improved by connecting VDD_ANT supply input to GND. Also an external TVS diode with low
capacitance (<0.5pF, e.g. Infineon ESD0P2RF) can be used to improve RF-input ESD capability.
With passive antenna the suggested power mode is LDO (default) since Switcher mode will reduce
sensitivity by about 4dB (typ.). Note that with an active antenna usage there is no effect of the power
mode used and both LDO and Switcher mode give equal performance.
2.2.6
Active GPS antenna
The customer may use an external active GPS antenna when antenna cable loss exceeds > 1dB.It is
suggested the active antenna has a net gain including cable loss in the range from +7 dB to +25 dB.
Specified sensitivity is measured with external low noise (NF<1dB, G>15dB) amplifier, which gives
about 2dB advantage in sensitivity when compared to a passive antenna.
An active antenna requires certain bias voltage, which can be supplied externally via VDD_ANT supply
input. De-couple externally the VDD_ANT input; see the application circuit diagram in chapter 6. The
external bias supply must provide limitation of the max current below 150mA during e.g. antenna signal
short circuit condition.
GTS-4E GPS Module Hardware Integration Manual
Suggested ON_OFF Hibernate control timing diagram.
Page 11 of 22
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