Spirent Federal’s CRPA Test System to Drive Next-Generation Military GPS User Equipment

Spirent Federal Systems, the world’s leading Positioning, Navigation and Timing (PNT) test solutions provider has recently supplied its CRPA Test System to an international defence, aerospace and security company BAE Systems for M-Code military GPS technology development.

BAE Systems will use Spirent Federal’s Controlled Reception Pattern Antenna (CRPA) Test System for developing the next generation of military GPS receivers. Spirent Federal CRPAs qualify to support the modernisation of advanced Military GPS User Equipment and in providing effective protection against jamming in high-interference environments.

Our team from THE GPS TIME had the exclusive email interview with Jeff Martin – VP Sales, Spirent Federal Systems in which he talks about the Challenges to CRPA testing in live locations, GNSS Vulnerability and new threats with technological advancements and what will be the next big market for CRPA Testing and much more.

What are Controlled Reception Pattern Antennas? What are they used for?

Controlled Reception (or Radiation) Pattern Antennas (CRPAs) are multi-element antenna systems that have the capability to adjust their algorithms according to conditions. Typical CRPA functionality includes two key capabilities:

  • Null-steering – where a CRPA identifies a threat and effectively rejects signals arriving from the identified direction
  • Beamforming – where a CRPA concentrates its gain in a particular direction/directions, achieving greater carrier-to-noise (C/No) for signals arriving from those identified areas.

The purpose of these functions is to offer greater resilience to threats such as jamming and spoofing through the intelligent null-steering, as well as to increase satellite availability and positioning performance through beamforming. Beamforming has been demonstrated to be able to make lower elevation satellites, that would otherwise be too weak to use, available to the positioning solution.

CRPAs are becoming more widely used. They represent the leading technology for jamming robustness, meaning any safety- and mission-critical system would be considered. Typical applications would include military aircraft, land vehicles and ships.

What are the Challenges to CRPA testing and challenges that occur while testing in live locations?

CRPA testing presents significant challenges. As with all GNSS technologies, lab testing should make up the overwhelming portion of testing. This involves powerful simulation capabilities, and should encompass both conducted and over-the-air chamber testing. Conducted testing is required to characterize and optimize the performance of the receiver electronics without the variable added by bringing the physical antenna into the test. Over-the-air testing that incorporates angle of arrival is then required to characterize the performance of the antenna elements. Test equipment must incorporate powerful and highly controllable signal generation, precise phase alignment, and flexible interference generation. The ability to transition satellite angle-of-arrival between “zones” of an anechoic chamber is a patented capability of Spirent, and adds powerful realism and extended scenario durations to CRPA testing.

Live testing on a range can be hugely expensive, and the introduction of a range of simulated signals and powerful interferers can play havoc with other nearby positioning systems. Open-air range testing has been known to interfere with commercial aircraft, for instance.

What are the elements of Spirent’s CRPA Test System and its unique features?

  • GSS9000 – the industry’s most powerful GNSS signal generator
  • Embedded interference – up to 130 dB jammer-to-signal ratio from the GSS9000
  • Powerful and user-friendly SimGEN simulation control software
  • The industry’s highest update rates and lowest latency for the ability to maintain specifications through extreme dynamics

    BAE has selected Spirent Federal CRPA Test System. Can you share what features to look for when selecting a CRPA system for purchase?
    • Proper number of RF outputs to meet antenna element requirements.
    • Critical to ensure proper phase calibration for both GNSS and interference across each RF output/element.
    • Multiple interference sources with high J/S ratio.  Important that noisefloor is realistic.
    • Simulator channel density (lots of available channels) to accurately simulate multiple GNSS satellites as well as multipath and spoofing signals.
    • Realistic vehicle dynamics for simulating the vehicle upon which the CRPA receiver is mounted.
    • Simulator should meet all signal requirements – GNSS, interference, secure signals such as Y-code, SAASM and M-code (for authorized users).
  • Talking about GNSS Vulnerability what new threats are seen with technological advancements like AI and 5G?

5G represents a new source of out-of-band interference. There are concerns that this will interfere with GNSS performance. Ligado is a newsworthy example of this.

What have been the mistakes while testing in the past, the emerging standards and what we can expect in the future?


Test environments that cannot properly manage calibration of phase (and other variables) across multiple CRPA elements.

Poor/unrealistically low power levels for simulated jammers.

Unrealistic noisefloor when combining jamming/interference with GNSS signals.

What to expect in the future:

Even higher power levels for interference/jamming.

Considering autonomous vehicles and drones what is going to be the next big market for CRPA Testing?

Autonomous vehicles


Commercial shipping

Commercial aircraft