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S-band is becoming a busy space for developers of position, navigation and timing (PNT) signals and equipment. With the L-band frequencies used by GPS and other GNSS constellations becoming crowded, more PNT services are taking advantage of S-band frequencies opened up by the International Telecommunications Union (ITU).
That’s bringing new complexity to PNT test engineers, who need to be able to simulate S-band signals faithfully, realistically and coherently with other signals in the lab. Spirent has addressed this requirement with PNT X, which supports the generation of live, future and custom S-band signals.
Example S-band use cases supported by PNT X
New internal upconverters within PNT X enable developers to generate and control native RF for S-band signals and equipment across multiple use cases, including current and planned regional GNSS constellations, alternative PNT solutions, and planned lunar navigation systems.
Regional GNSS constellations offer additional coverage to complement global GNSS systems and to enhance accuracy, particularly in areas with a constrained view of the sky. Three constellations are currently transmitting on S-band frequencies or have S-band signals planned:
NavIC: The Indian regional constellation, formerly IRNSS, is fully operational and transmitting in the S-band with a carrier frequency of 2492.028 MHz, in addition to its L1 and L5 signals.
QZSS: The Japanese regional constellation’s QZSS Safety Confirmation Service (Q-ANPI), for use in disasters, transmits in the S-band with a centre frequency of 2GHz. It also uses the S-band for inter-satellite ranging between its geostationary satellites.
KPS: The Korean Positioning System (KPS) is a planned new regional constellation scheduled to begin transmitting in the S-band in 2027.
Alternative PNT signals are also starting to operate on S-band frequencies. One interesting example is Locata—a ground-based system that offers GNSS-like positioning, but without the atomic clocks used for precise timing and synchronisation between GNSS satellites. Locata has a published ICD and is primarily targeting indoor positioning and precise positioning services.
Lunar PNT is an exciting new frontier in satellite navigation. While today’s lunar missions rely on signals from the GNSS constellations orbiting the Earth, a cooperation of major space agencies is planning an independent, navigation system, LunaNet, delivered to the Moon’s surface from satellites orbiting the Moon. LunaNet will transmit in the 2483.5-2500 MHz S-band range, chosen for its safe distance from radio astronomy frequencies.
How PNT X helps with S-band testing
PNT X has many features that make it an ideal simulation platform for developers of S-band signals, services and receiver equipment, including:
Native S-band support: PNT X can support all S-band PNT signals that have published Interface Control Documents (ICDs), including NavIC, Q-ANPI and Locata, enabling developers to evaluate receiver handling of S-band signals either alongside or independently of L-band signals.
Huge channel capacity: PNT X can generate up to 640 independent signals simultaneously, giving developers huge flexibility when building test scenarios. As well as generating signals from all live global and regional GNSS constellations, PNT X also offers a wide range of RF interference waveforms as standard, with continuous dynamic range for ultra-realistic jamming and spoofing scenarios.
Future and custom signals support: For developers working on future and custom S-band signals, PNT X offers three powerful capabilities: SimIQ, SimIQ spatial awareness and Flex.
Inject custom I/Q files: The SimIQ feature of PNT X enables custom S-band signals to be injected as I/Q files and converted to RF. This means developers can simulate their custom signals alongside GNSS, LEO and other PNT signals, and interference waveforms.
Apply realistic effects to I/Q-defined transmitters: SimIQ spatial awareness automatically applies environmental effects to signals injected as I/Q files, according to the parameters of the test scenario. Effects include power levels, Doppler offsets and signal delays, bringing more realism to test scenarios and delivering more insightful test results. The same I/Q file can also be used to define multiple independent transmitters, with effects applied realistically to each one—saving time and cutting down on data storage and transfer.
Define custom S-band signals: The Flex feature of PNT X enables developers to generate their own custom RF signals directly within the simulator. Signal attributes that can be customised include modulation type, centre frequency, signal offsets and navigation data. The custom S-band signal can then be generated alongside GNSS and other signals included as standard in PNT X.
Model realistic environments: PNT X brings new realism to PNT testing through its 3D terrain modeling capabilities. Imported 3D maps can be used to define the physical environment of the test scenario, and transmitters and receivers can be placed within it. PNT X applies the resulting environmental effects—such as multipath, signal obscuration and signal diffraction—automatically to the signals and equipment under test, including to signals generated from injected I/Q files.
PNT X: Bringing unprecedented flexibility and realism to S-band testing
Flexible S-band support is just one of the many groundbreaking features offered in PNT X, the world’s most advanced PNT simulator. Designed to test today’s mission-critical signals and equipment to the limit, PNT X brings unprecedented realism to the PNT test lab, enabling more testing to be done earlier and fostering utmost confidence in the test results.
If you’d like to learn more about Spirent PNT X, watch the video or visit the website.
