AIR7310-B GNSS Guide¶

The AIR7310-B advanced software-defined radio (SDR) platform is equipped with a premium, industrial grade multi-band global navigation system (GNSS) receiver that provides nanosecond-level timing accuracy and performs anti-jam and anti-spoof countermeasures.

Table 1: Internal AIR7310-B GNSS/GPS Overview

Parameter	Value
Connector Type	Front Panel SMA Connector
Crystal Oscillator	TCXO
Antenna	Active (3.3V DC Bias, 2-20mA Typ, active current limit ~70mA)
1 PPS Accuracy	5 ns to UTC
GNSS Reception Capability	GPS L1C/A, L5 QZSS L1C/A, L5 GAL E1B/C, E5a BDS B1I, B1C, B2a NavIC L5 GLO L1OF SBAS L1C/A: WAAS, EGNOS, MSAS, GAGAN
Anti-jam	Active CW detection and removal Dual onboard bandpass filters
Anti-spoof	Advanced anti-spoofing algorithms Galileo OSNMA
Horizontal Position Accuracy (CEP)	1.5 m (standalone mode)

Receiver Performance¶

Table 2: Receiver Sensitivity for Supported GNSS Modes

Parameter	Mode	GPS+GLO+GAL+BDS
Sensitivity	Tracking and Navigation	-167 dBm
	Reacquisition	-160 dBm
	Cold Start	-148 dBm
	Hot Start	-157 dBm

Table 3: Receiver Performance Across Supported GNSS Modes

Mode	Cold Start Acquisition	Hot Start Acquisition	Aided Start Acquisition	Max Update Rate
GPS+GLO+GAL+BDS	24 s	2 s	2 s	8 Hz
GPS+BDS+GAL	25 s	2 s	2 s	10 Hz
GPS+GAL	29 s	2 s	2 s	15 Hz
GPS+GLO	26 s	2 s	2 s	15 Hz
GPS+BDS	28 s	2 s	2 s	12 Hz
GPS	29 s	2 s	2 s	20 Hz

Electronic Protection Against Interference and Jamming¶

The GNSS receiver on the AIR7310-B is capable of mitigating the negative impact of jamming signals. The receiver has active CW detection and removal, as well as dual onboard band pass filters to address this and maintain lock. In addition, the receiver has advanced anti-spoofing algorithms and Galileo OSNMA (Open Service Navigation Message Authentication) to ensure secure end-to-end transmissions from Galileo satellites to GNSS receivers.

1PPS Performance¶

Table 4: Timing Performance

Parameter	Locked	Holdover (< 1 hour)	Holdover (< 24 hours)
1PPS Accuracy	<5 ns	<±180 usec	<±4.32 msec
1PPS Stability (1-σ)	<4 ns	-	-

Antenna Selection¶

Table 5 below details the supported GNSS constellations and their associated signals and center frequencies.

Table 5: Supported GNSS Constellations

GNSS	Signal	Center Frequency
GPS / QZSS	L1C/A L5	1575.42 MHz 1176.45 MHz
GLONASS	L1OF	1602 MHz (15 Channels)
Galileo	E1-B/C E5a	1575.42 MHz 1176.45 MHz
BeiDou	B1I B1C B2a	1561.098 MHz 1575.42 MHz 1176.45 MHz
NavIC	SPS-L5	1176.45 MHz

Table 6 below outlines the recommended dual band active antenna specifications for the supported GNSS signal types. The voltage to power the antenna pre-amplifier is superimposed (biased) on the antenna connector. In a deployment where multiple AIR7310-B radios are needed, only a single GNSS antenna is necessary.

Table 6: Recommended GNSS Antenna Specifications

Parameter	Value	Note
Antenna Gain	30dB (min) 40dB (max)	Including cable loss
Noise Figure	3 dB	Including LNA (external or internal)
Group Delay Variation	10 ns (max)	Inter-signal requirement 50 ns (max)
L1 Band Gain	3 dBic
L2/E5a Band Gain	2 dBic
L5/E5a Band Gain	2 dBic
Polarization	RHCP
Axial Ratio	2 dB max, at Zenith
ESD Circuit Protection	15 kV human body model air discharge
Impedance	50 Ohms

Software Interface¶

GPSd Interface¶

AirStack provides software support for the GNSS disciplined oscillator via the GPSd service daemon. This allows for the AIR-T to leverage the system for position, Network Time Protocol (NTP), and many other common features for GPS.

A full list of the GPSd manual pages that describe the operation may be found here. For example, to dump the raw NEMA message to the terminal screen, use the command:

$ gpspipe -r

To view the GPS data stream output in a table, use the command

$ gpsmon

GNSS as the Reference¶

The SoapyAIRT driver in AirStack can easily leverage the GNSS disciplined oscillator as a frequency reference. This may be done by setting the clock source to GPS using the setClockSource method:

sdr = SoapySDR.Device(dict(driver="SoapyAIRT"))
try:
    sdr.setClockSource("GPS")
except RuntimeError as e:
    print("GPS Clock Reference Failed!")
    print(e)
    sdr.setClockSource("internal")

For more information, see the External Clock Reference application note.