Enhancing GNSS Resilience: Testing CRPA Enabled Receivers for Space and Defense Applications
As the space industry gathers at Small Satellite Conference, attention turns to the growing importance of Global Navigation Satellite Systems (GNSS) in delivering Positioning, Navigation, and Timing (PNT) services. From low Earth orbit satellite networks to terrestrial autonomous systems, GNSS plays a foundational role. Yet as reliance on satellite navigation increases, so too does the threat of jamming and spoofing. Controlled Reception Pattern Antenna (CRPA) technology offers a powerful solution, and Keysight’s integrated testing platform enables engineers to design and validate robust CRPA enabled GNSS receivers under realistic and extreme conditions.
GNSS signals travel approximately 20,000 km from satellites in medium Earth orbit and reach the Earth’s surface with power levels as low as -130 to -160 dBm. This makes them highly susceptible to both intentional interference (jamming) and deceptive signal attacks (spoofing). In 2022 alone, incidents of GNSS interference near conflict zones increased by over 500 percent, with spoofing attacks increasingly targeting commercial aviation, maritime operations, and space assets.
While conventional GNSS receivers use a single omnidirectional antenna, CRPA systems employ multiple antennas to actively suppress interference. By identifying the direction of hostile signals and steering nulls toward them, CRPA enabled receivers can maintain signal integrity and accurate navigation even in contested environments.
Developing and validating CRPA enabled receivers is significantly more complex than working with single antenna systems. Each antenna in the CRPA array must receive a unique, phase coherent signal that reflects its spatial orientation and motion relative to the GNSS satellite constellation. This spatial separation requires real-time simulation of multi-frequency, multi-constellation GNSS signals, all while maintaining precise timing and phase synchronization. The testing system must deliver sub-degree phase alignment across channels to ensure accurate beamforming and null steering. Accurate modeling of satellite trajectories, Doppler effects, antenna baselines, and relative motion is essential to emulate the true RF environment. The simulator must also accommodate complex signal environments with high-interference dynamics, such as frequency agile jammers and time-varying spoofing attacks. Even small deviations in signal timing or phase on the order of a few nanoseconds or degrees can degrade system performance, making the receiver unable to reject interference or differentiate between authentic and spoofed signals. Additionally, real-world CRPA testing often involves dynamic scenarios like aircraft banking maneuvers, vehicle turns, or space vehicle reorientation. These demand a test solution capable of generating motion-adaptive signal profiles in real-time, while ensuring that phase coherence is not compromised. Without this level of fidelity and realism, test results may misrepresent how a CRPA receiver would perform under operational stress.
To meet these challenges, Keysight, in collaboration with Syntony, has developed a flexible and scalable CRPA testing platform. It combines the R4454A Constellator GNSS Simulator with the M9484C VXG-C Vector Signal Generator, delivering high fidelity, phase aligned signals to each antenna element under test. The system supports simulation of all major GNSS constellations, real-time synchronization across multiple channels, and signal-to-interference ratios up to 151 dB. The VXG-C supports L- and S-band frequencies with bandwidths up to 2.5 GHz. While it offers a wide bandwidth range, most GNSS signals occupy a much narrower spectrum, typically between 10 MHz and 50 MHz.
The system’s modular architecture allows users to scale up by synchronizing multiple VXG-C chassis, making it suitable for CRPA arrays ranging from four to sixteen antennas or more.
In defense environments, GNSS reliability is not merely a matter of convenience. It is a mission critical requirement. From precision navigation and targeting to synchronized battlefield operations, PNT data underpins nearly every layer of modern military capability. However, in today's increasingly congested and contested electromagnetic spectrum, GNSS signals are frequent targets for disruption. CRPA enabled receivers offer a tactical edge, and Keysight’s test solution is designed specifically to evaluate their performance under battlefield realistic conditions.
Ground vehicle navigation and convoy coordination also benefit from CRPA testing. In regions such as the Sahel, where adversaries deploy low-cost jammers to disrupt troop movements, maintaining real-time location and timing sync across dispersed units is essential. Keysight’s test platform enables simulation of vehicle movement through interference rich corridors, such as urban centers with known jammer activity, allowing developers to test CRPA systems under convoy like dynamic motion and signal multipath.
Another critical scenario involves missile and guided munition systems, where GNSS data is used for mid-course correction and terminal guidance. In one test program, a CRPA enabled receiver was subjected to multiple dynamic spoofing attacks mimicking adversarial deception strategies. The system was able to distinguish authentic GNSS signals from falsified ones by angle of arrival and maintain its targeting integrity. These capabilities are essential for next generation strike systems operating in denied environments.
Space-based defense assets, such as low Earth orbit surveillance and reconnaissance satellites, also face RF interference risks, particularly when passing over conflict zones. Using Keysight’s system, engineers can simulate a full orbital profile with GNSS satellite visibility changes, Doppler shifts, and regional jamming to verify the receiver’s ability to reacquire signals after loss or spoofing events.
Built-in support for hardware in the loop testing enables real-time communication between the simulator and the Device Under Test, with effectively zero latency. Phase calibration and fixture de-embedding tools ensure that signal coherence is maintained from the simulator output to the antenna inputs, allowing precise evaluation of beamforming and nulling performance. Software defined architecture allows the R4454A Constellator to remain up to date with emerging GNSS standards and threats. Engineers can script custom test scenarios or automate sequences to accelerate both development and validation workflows.
As both civilian and military systems become more dependent on uninterrupted satellite navigation, the consequences of GNSS signal loss are becoming increasingly severe. A 2023 UK study estimated that a single day of GNSS outage would cost the British economy over 1.5 billion pounds. The risks are not hypothetical. Incidents involving GNSS spoofing have affected commercial ships in the Black Sea, aircraft over the Middle East, and scientific missions in polar regions. The need for robust, field-ready CRPA GNSS receivers is clear. Testing them accurately before deployment is critical.
At Small Satellite, discussions around GNSS security and interference resilience are more than just technical. They are strategic. Keysight’s scalable, high-fidelity CRPA test platform provides engineers with the tools they need to validate next generation GNSS receivers and ensure their performance in the face of growing threats. From real-time orbital simulation to complex urban interference testing, the solution bridges the gap between lab and mission. To explore how this system fits into your workflow, explore products in our CRPA-enabled GNSS receiver test solution.