10
10
AsteRx-i OEM GNSS Module
10
2.4
RF Interface
The main antenna must be connected to the ANTA u.FL and the auxiliary antenna must
be connected to the ANTB u.FL connector.
2.4.1
Electrical Specifications
Antenna supply voltage
3-5.5V DC, set via pin#18 of the 30-pin connector. The DC
voltage is applied to both antenna connectors.
If pin#18 is not connected, there is no DC voltage to the
antennas.
ANTA DC series impedance
< 2.2 Ohms
ANTB DC series impedance
< 4 Ohms
Guaranteed antenna current
(ANTA or ANTB)
200 mA
Antenna current limit (ANTA or
ANTB)
< 300 mA
Antenna net gain range
1
15-45 dB
For optimal performances, the net gain on ANTA and ANTB
must not differ by more than 10dB.
Receiver noise figure
(NFrx, see below)
10 dB (with 15-dB net gain)
The receiver noise figure increases as the net gain increases,
but its contribution to the system noise figure decreases.
The worse case is for a net gain of 15dB.
RF nominal input impedance
50 Ohms
VSWR (ANTA or ANTB)
< 2.5:1 in 1200-1251 MHz and 1560-1610 MHz range
1
The net gain is the total pre-amplification of the distribution network in front of the receiver. Typically, this
equals antenna active LNA gain minus coax losses in the applicable GNSS bands.
2.4.2
System Noise Figure and C/N0
The system noise figure, in dB, can be calculated as:
NFsys = 10*log
10
(10
NFant/10
+ (10
NFrx/10
-1)/10
Gpreamp/10
)
where
•
NFant is the antenna LNA noise figure, in dB.
•
NFrx is the receiver noise figure, in dB. NFrx depends on the net gain, but a good
approximation (<0.5dB) of NFsys can be obtained by setting NFrx = 10dB.
•
Gpreamp is the net gain in front of the receiver, in dB.
