October 3, 2024
Ricardo Verdeguer Moreno
Radio frequency (RF) jamming is one of the most prevalent threats to navigation equipment, especially in navigation warfare (NAVWAR) scenarios. Developers of receiver equipment therefore want to know how, realistically, the receiver will respond to the presence of jamming interference.
In particular, developers often need to understand the impact on the receiver in dynamic scenarios where the device under test (DUT) is moving into or out of range of one or more high-powered jammers. However, reproducing such conditions realistically in the lab is tricky.
One issue lies with the need to simulate signals at very different power levels. Noise from a jammer can be many times louder than GNSS signals, which are typically -130dBm at the receiver. This is particularly true of the high-powered jammers typically deployed by nation states.
Generating low-power GNSS signals and high-power jamming signals within the same simulator unit creates a technological challenge, however. There is a risk that very loud jammer noise may leak into the channels producing GNSS signals, affecting the reliability of test results.
Typically, this has meant that simulators have only been able to produce jamming signals in a restricted power range. While this can still provide valuable insights into receiver behaviour, it represents a compromise in terms of test realism.
It’s an issue that Spirent has addressed by placing GNSS signals and jamming waveforms on different radio cards, effectively isolating them from each other. Using this approach our PNT X platform uniquely offers developers the ability to achieve very high J/S ratios within the same simulator unit: up to 150 dBm of difference between the jammer signal and the GNSS signal.
This allows even the most powerful jammers to be emulated realistically in the lab without requiring a separate interference generator and all of the complexity and cost that come with it.
Additionally, PNT X has slots for up to 10 radio cards, each with 64 channels of output. This means the simulator is capable of generating RF on up to 640 channels—ideal for testing mission-critical scenarios in complex RF environments with multiple jamming sources.
Another consideration is that in real-world scenarios, the J/S ratio is usually not constant, but dynamic based on the position of the receiver relative to the jammer. In the case of an aircraft flying into a conflict zone, for example, jammer noise may start off quieter than the GNSS signal, get louder as the aircraft gets closer to the jammer, and tail off as the aircraft exits the jammer’s range.
In some conflict zones, there may be more than one jammer in the vicinity of the receiver at any given time. This creates a complex RF environment with rapidly-fluctuating jamming signals as the receiver moves through the zone. To reproduce these conditions accurately in the lab, the simulator needs to be capable of stimulating multiple, dynamic J/S ratios within a wide dB range.
To address this challenge, PNT X uniquely offers developers a continuous dynamic range of up to 140 dBm. This enables the power of the simulated jamming waveforms to fluctuate within a range starting from lower than GNSS at -130 dBm (producing a negative J/S ratio) to levels around the 0 dBm typical of the highest-power jammers.
While this is extremely difficult to achieve technologically, PNT X makes it possible by splitting the power range across separate radio cards, and switching seamlessly between them in test scenarios that require J/S ratios to fluctuate rapidly within a broad range.
The continuous dynamic range in PNT X becomes especially powerful when used in conjunction with other capabilities of this ground-breaking new simulator platform, including:
Inject custom I/Q files with SimIQ: The SimIQ tool enables custom waveforms to be injected as I/Q files and upconverted to RF in the simulator. This allows developers to simulate custom or proprietary jamming signatures alongside GNSS, LEO and other PNT signals within the platform.
Define multiple jammers with one I/Q file: The same I/Q file can also be used to define multiple independent transmitters, supporting NAVWAR scenarios featuring multiple jamming sources. Spirent’s patented SimIQ spatial awareness feature automatically applies realistic effects like power levels, Doppler shift and signal delay to I/Q-defined jammers during the test scenario.
Model realistic environments: The 3D terrain modeling feature in PNT X enables developers to define the physical environment of the test scenario and place transmitters and receivers within it. Effects such as multipath, signal obscuration and signal diffraction are applied automatically to the signals and equipment under test, including to signals and waveforms generated from injected I/Q files, further increasing the realism of the test scenario.
Continuous dynamic range is just one of the many powerful features offered in PNT X, the world’s most advanced PNT simulator. PNT X brings unprecedented flexibility and realism to vulnerabilities testing, enabling more testing to be completed in the lab before moving to validation in a live environment.
To learn more about Spirent PNT X, contact us.
