May 17, 2025
Dean Kemp
In January, the US State Department announced plans to remove some Controlled Reception Pattern Antennas (CRPAs) from the US Munitions List (USML), starting this September.
This will enable those CRPAs to be exported under Export Administration Regulations (EAR), rather than the much stricter International Traffic in Arms Regulations (ITAR).
The relaxation of export restrictions means these anti-interference antennas will become more readily accessible for civil as well as military applications—which will help to protect infrastructure and vehicles against the widening threats of GNSS jamming and spoofing.
Spirent recently hosted a webinar to review these developments and offer guidance to GNSS systems developers on how to integrate a CRPA into a layered resilience strategy. Below is a summary of the key points, and you can watch the webinar on demand.
Our first guest speaker was Dr Andriy Konovaltsev, Research Assistant at the German Aerospace Center (DLR), who explained how CRPAs and array antennas work.
Both are formed of multiple individual antenna elements, ranging from three to eight or more. Both contain electronics that can be programmed to identify an interference signal and steer a null in its direction and can also direct antenna beams towards genuine signals. The null rejects the interference signal prior to the correlation phase, where the receiver compares the perceived signals with its internal model in order to calculate a position. The beamforming significantly enhances the receiver’s ability to calculate an accurate position in the presence of jamming, spoofing and multipath.
A key difference is that an array antenna requires multiple cable connections to the receiver, while a CRPA uses only one. This means a CRPA can be retrofitted to an existing receiver, but an array antenna requires a new receiver, which can make it a costly solution.
Andriy shared interesting results gained from testing CRPAs and array antenna designs using Spirent simulators. He showed that combining pre-correlation and post-correlation techniques can deliver significantly greater resilience to interference, making these systems extremely effective in adversarial environments.
Next, Lorenzo Danelli, Radio Navigation Engineer at Thales Alenia Space, talked about how CRPAs can be used to protect critical national infrastructure against the growing threats of jamming and spoofing.
Again, drawing a distinction between pre-correlation (null steering) and post-correlation (beamforming) techniques, he showed how different antenna designs can be used to build resilience into receivers designed for applications like precision agriculture, train navigation and ground reference stations.
Lorenzo also provided an insight into how Thales Alenia Space approaches the work of designing a new CRPA or array antenna. Much of the initial work is carried out using a digital twin, but at a certain point this advances to a hardware prototype which must be tested.
Here, simulation is an essential step before taking the design into the real world or field testing. Lorenzo showed how his team uses Spirent simulation to simulate the GNSS signals and the interference. This allows Thales Alenia Space to model and repeat scenarios and corner cases which would be difficult or impossible to test in the real world.
Finally, for real-world testing, the team take advantage of events like Norway’s annual Jammertest to put the hardware through its paces in an open sky environment.
Our third speaker was Neil Gerein, VP of Product, Aerospace and Defense, at Hexagon Autonomy and Positioning. Neil is another Jammertest aficionado, but he stressed that open sky testing is the last stage in a test regimen that must be carried out for the most part in the lab.
In a live test you only get one shot, he explained, whereas in the lab you can repeat the same conditions again and again. If the CRPA doesn’t perform as expected the first time, you can run the same scenario again after making modifications—a discipline Neil expressed as: ‘measure, improve, and re-measure’.
Hexagon’s customers are operating in some of the world’s most challenging signal environments, and as jamming and spoofing grow in sophistication, Hexagon must keep innovating to ensure its antennas can handle new threats. Neil walked us through the way the company tested its small-footprint GAJT 310 three-element antenna system.
Testing involves measuring the antenna patterns in an anechoic chamber and incorporating them in conducted testing using a Spirent system. This setup allows the CRPA to be evaluated across a wide range of signal conditions, interference scenarios, and motion profiles – including waveforms designed to simulate emerging interference threats.
Finally, I provided an overview of the challenges involved in CRPA selection and testing, as well as the key test methods available, and why realism in lab testing is essential.
Challenges include the fact that interference and navigation warfare (NAVWAR) threats are evolving all the time. A single NAVWAR attack may involve multiple jammers and spoofers, for example, with some ground-based and some airborne. In response, position, navigation, and timing (PNT) systems are becoming much more sophisticated, often using an array of different sensor types and multiple GNSS constellations and frequencies to increase resilience.
While CRPAs offer powerful protection against interference, they’re not a silver bullet. A CRPA should be just one part of a layered defense strategy against jamming, spoofing and other interference threats. When choosing and testing a CRPA for integration, then, it’s important to use a simulator platform capable of testing the CRPA platform in the full range of scenarios it is likely to encounter in the real world.
It’s also important to choose the right test method at the right stage of the product lifecycle. CRPA hardware can be tested with conducted simulated signals, with simulated signals broadcast over the air in an anechoic chamber, and with real signals on an open sky test range.
Each method has its place. Conducted testing allows developers to assess the performance of algorithms without bringing the potential variable of the antenna hardware into the equation; chamber testing enables the antenna hardware to be tested while maintaining full control of the test environment; and open sky testing is vital to validate earlier testing in the real world.
As CRPAs become more accessible for a greater range of applications, knowing how to choose the right design and assure its performance will be essential. This webinar provides a comprehensive insight into why and how to use CRPAs for GNSS resilience, and how to get the best out of your CRPA testing regimen. Watch the full webinar recording.
Spirent has been at the forefront of CRPA testing since the mid-1980s, evolving our simulator platforms and test resources as the technology and the threat landscape have evolved. If you have any questions about choosing, evaluating or integrating a CRPA, please contact us.
