NEO-D9S - Integration manual
The antenna system should include filtering to ensure adequate protection from nearby
transmitters. Care should be taken in the selection of antennas placed close to cellular or Wi-Fi
transmitting antennas.
4.2.1 Antenna bias
The bias-t inductor must be chosen for multi-band operation, a value of 47 nH ±5% is
recommended for the recommended Murata L part. It has a self-resonance frequency of 1
GHz and a high impedance (> 500 Ω) at L-band frequencies.
The recommended bias-t inductor (Murata LQG15HS47NJ02) has a maximum current capacity of
300 mA. Hence the current is limited to 70 mA at 3.3V using an active limiter in the recommended
circuit shown in
below. A 10 Ω resistor (R2) is provided to measure the current. This resistor
power rating must be chosen to ensure reliability in the chosen circuit design.
Figure 15: NEO-D9S antenna bias inductor impedance
A recommended circuit design for an active antenna bias is shown below. This example shows an
external voltage of 3.3 V with current limiting as described above. An ESD protection diode should
also be connected to the input as shown.
UBX-19026111 - R07
4 Design
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