Active Antenna - Fibocom GTS-4E-00 Hardware Integration Manual

Typically a passive antenna is located near electronic components; therefore care should be taken to
reduce electrical 'noise' that may interfere with the antenna performance. Passive antennas do not
require a DC bias voltage and can be directly connected to the RF input pin RF_IN. Sometimes, they
may also need a passive matching network to match the impedance to 50 Ohms.
Note:

Some passive antenna designs present a DC short to the RF input, when connected. If a system is
designed with antenna bias supply AND there is a chance of a passive antenna being connected to
the design, consider a short circuit protection.

All GTS-4E receivers have a built-in LNA required for passive antennas.

Active Antenna

5.4.2
Active antennas have an integrated low-noise amplifier. They can be directly connected to RF_IN. If an
active antenna is connected to RF_IN, the integrated low-noise amplifier of the antenna needs to be
supplied with the correct voltage through an external inductor. Usually, the supply voltage is fed to the
antenna through the coaxial RF cable. Active antennas require a power supply that will contribute to the
total GPS system power consumption budget with additional 5 to 20 mA typically. Inside the antenna,
the DC component on the inner conductor will be separated from the RF signal and routed to the supply
pin of the LNA.
Generally an active antenna is easier to integrate into a system design, as it is less sensitive to
jamming compared to a passive antenna. But an active antenna must also be placed far from any noise
sources to have good performance.
Note:

Antennas should only be connected to the receiver when the receiver is not powered. Do not
connect or disconnect the Antenna when the GTS-4E receiver is running as the receiver calibrates
the noise floor on power-up. Connecting the antenna after power-up can result in prolonged
acquisition time.

Supply voltage Should connect to RF_IN by inductor.

To test GPS signal reacquisition, it is recommended to physically block the signal to the antenna,
rather than disconnecting and reconnecting the receiver.
GTS-4E GPS Module Hardware Integration Manual
Figure 9：Active antenna biasing
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