LEA-6 / NEO-6 / MAX-6 - Hardware Integration Manual
UBX-14054794
Production Information
Design-in
Page 43 of 85
2.6.1
Passive antenna
A design using a passive antenna requires more attention regarding the layout of the RF section. 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
.
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 u-blox 6 receivers have a built-in LNA required for passive antennas.
Consider optional ESD protection (see
section 3.3).
2.6.2
Active antenna (LEA-6)
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 pin
V_ANT
. 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 (see Figure 41).
Figure 41: Active antenna biasing (for exact pin orientation see data sheet)
Generally an active antenna is easier to integrate into a system design, but an active antenna must also be
placed far from any noise sources to have good performance.
Antennas should only be connected to the receiver when the receiver is not powered. Do not
connect or disconnect the Antenna when the u-blox 6 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.
Never feed supply voltage into RF_IN on u-blox LEA-6 modules. Always feed via V_ANT.
To test GPS signal reacquisition, it is recommended to physically block the signal to the antenna, rather
than disconnecting and reconnecting the receiver.
Consider optional ESD protection; see
section 3.3 for more information.
