Anti-jam systems: Which one works for you?

June 14, 2017  - By

In my April column, I introduced the basic concepts behind GPS anti-jam technology, along with a bit of history around its evolution. I knew this was a popular topic, but I didn’t anticipate the enormous amount of positive correspondence I’ve received since, including many inquiries about where to buy this technology and who is entitled to have it.

So this month we return to the controlled reception pattern antenna (CRPA) topic, to look specifically at the major suppliers of GNSS anti-jam technology in a bid to help you select the best fit for your requirements.

As mentioned in April, CRPAs can trace their roots back to military radar developments in the 1970s and 1980s. It’s no surprise, then, that the main players in the CRPA market tend to be large defense primes. But there are many smaller companies, universities and research institutions that also play in the CRPA arena these days.

What about export?

When GNSS jamming was a little-known military problem, the situation was simple: anti-jam was a military technology for military applications only. Later, as GPS evolved into a dual-use technology, critical infrastructure and civilian applications brought a new demand for anti-jam in non-military domains.

Confusion then abounded about who exactly is entitled to make use of anti-jam technology. There are two distinct factors here: security classification, and export control. Let’s clear these up.

Security classification is simple: If a product is classified, it is only available to customers who hold the appropriate level of security clearance. Usually it is the performance and vulnerabilities of a product that would attract a classified status. As you might expect for in-service military products, the military would not wish everyone to know the performance and weaknesses of its deployed technology. This is why many datasheets for CRPAs omit performance information.

The second issue is export control. This, of course, varies by country. In the U.S., a CRPA developed towards a defense program is likely to have International Traffic in Arms Regulations (ITAR) restrictions attached to it. In Canada, CRPAs are subject to the Controlled Goods Program. In the UK, CRPAs sit on the “dual-use” export control list, which recognizes that CRPAs have both military and non-military application. An export license is usually required.

Before I go any further, a little disclaimer: I am not making any product recommendations in this article. There are many things to consider when choosing anti-jam technology, and you should always consult a navigation warfare expert and carry out appropriate evaluations prior to choosing a product. You should also seek guidance from your own government regarding any restrictions on export or import.

With that out of the way, let’s look at the offerings of a few suppliers. This is by no means a complete list, but I did manage to catch up with a few of the major players to ask them about their anti-jam technology offerings.


I spoke with Peter Soar, business development manager, Military and Defence, at NovAtel about NovAtel’s offerings.

Peter Soar: “The GAJT-710 series are retrofittable GPS anti-jam products that combine a seven-element controlled reception pattern antenna (CRPA) and the antenna electronics in a single unit. The GAJT-AE-N is a GPS anti-jam antenna electronics system that supports a separated four-element antenna.”

Main features: “All three products protect the GPS L1 and L2 bands simultaneously, and are suitable for military (SAASM) receivers as well as open-signal receivers, normal civil receivers and ‘survey grade’ receivers. The wideband design means that the units are ready for M-code. In the GAJT-710, there are seven antenna elements for up to six independent nulls on both frequencies, and the GAJT-AE-N supports four antenna elements, for up to three independent nulls. All products use space-frequency adaptive processing for increased degrees of freedom. System messages provide an indication of jamming presence, even when the nulling is defeating the jamming.”

Intended market: “GAJT-710ML is optimized for land use, while GAJT-710MS is used for maritime and littoral applications. Both types are currently in use on mobile platforms and fixed installations. The GAJT-AE-N is optimized for smaller platforms such as unmanned air vehicles, and is currently in use on a variety of platforms. GAJT products have been shipped to customers in 16 countries to date.”

Example customers: “The GAJT-700ML (a predecessor to the 710ML) was selected for trials by the Canadian Army through the Build in Canada Innovation Program, with exercises performed on the Artillery Observation Post Vehicle (LAV III OPV). Both GAJT variants were selected for field testing by the U.S. Army Communication-Electronics Research Development and Engineering Center (CERDEC) through the U.S. Army Rapid Innovation Fund. The United States Naval Observatory (USNO) selected the GAJT-710ML to satisfy a requirement at sites throughout the Department of Defense Information Network (DoDIN). The GAJT-AE-N is deployed on the Schiebel Camcopter S-100, and was also selected for testing on the M777C1 Howitzer by the Canadian Army.”

Situation with regards to export: “All GAJTs are designed and built in Canada. As such, they are subject to the Controlled Goods Program of Canada, but they are free from ITAR for non-U.S. customers.”

Raytheon UK

Some Raytheon products were mentioned briefly in the April column; I caught up with Alan Wright, business development executive, Force Protection, to get the latest information.

Alan Wright: “Raytheon UK offers a range of anti-jamming products ranging from high-performance products with multiple-element CRPAs to low size, weight and power products. Our current product lines utilize either analog or digital technologies to suit specific end-user requirements.”



Key Features

GAS-1 Analog technology, 7 antenna elements, switchable L1/L2 protection, minimal quiescent time delay, nulling, J/N, M-code signal bandwidth, AE/antenna integrated variant, fiber optic output variant.
ADAP Digital technology, 7 antenna elements, simultaneous L1/L2 protection, STAP, nulling, J/N, jamming flag, M-code signal bandwidth, AE/antenna integrated variant, fiber optic output variant.
SAS Digital technology, 5 antenna elements, simultaneous L1/L2 protection, low size, weight & power, STAP, nulling, J/N, direction finding, anti-spoof, jamming flag, M-code signal bandwidth.
Landshield   Digital technology, integrated 4-element antenna, simultaneous L1/L2 protection, low size, weight and power, STAP, nulling, J/N, direction finding, anti-spoof, jamming flag, M-code signal bandwidth, switched antenna variant.
MiniGAS   Analog technology, integrated 4-element antenna, simultaneous L1/L2 protection or L1 with L2 passthrough, low size, weight and power, minimal quiescent time delay, nulling, jamming flag.
MicroGAS Analog technology, integrated 2-element antenna, simultaneous L1/L2 protection, very low size, weight and power, minimal quiescent time delay, nulling.

Intended market: “With over 25 years’ experience, Raytheon UK is a world leader in the development, production and supply of GPS Anti-Jamming (GPS-AJ) systems to the majority of the world’s military forces (including the U.S. DoD and UK MOD), with solutions developed and certified for air, maritime and land applications. Raytheon UK has designed and manufactured in excess of 10,000 GPS anti-jam units for the worldwide market.”

Situation with regards to export: “GAS-1, ADAP and SAS are subject to U.S. ITAR restrictions. Landshield, MiniGAS and MicroGAS are free from ITAR and subject to UK export control.”

Rockwell Collins

I spoke with Al Simon, business development for navigation products/solutions, to get the latest on Rockwell Collins’ offerings. Rockwell’s portfolio includes some CRPA products aimed specifically at weapons. Al kindly provided the following table to summarize:




Key Features

Integrated GPS Anti-Jam System (IGAS) Weapons (Embedded) GPS receiver + AJ, nulling and beamforming, spatial, 20 in3, <2 lbs, up to 4 RF antenna inputs, 90+ dB J/S performance *, GPS (simultaneous L1 & L2), path to M-code
Strategic Anti-Jam Beamforming Receiver (SABR) Weapons (Embedded) GPS receiver + AJ, nulling and beamforming, STAP, 46 in3, <3 lbs, up to 7 RF antenna inputs, 120+ dB J/S performance*, GPS (simultaneous L1 & L2), path to M-code
NavStorm+   Weapons Nulling, spatial, 6.9 in3, <.6 lbs, up to 5 RF antenna inputs, 20,000 G shock, 90+ dB J/S performance*, GPS (simultaneous L1 & L2), path to M-code
NavFire Weapons Nulling, spatial, 2 in3, <.2 lbs, 1 or 2  RF antenna inputs, 25,000 G shock, 85+ dB J/S performance*, GPS (L1 or L2), path to M-code
DIGAR-200 Airborne, Maritime, Ground Nulling and beamforming, spatial, 218 in3, <11 lbs, up to 7 RF antenna inputs, 110+ dB J/S performance*, GPS (simultaneous L1 & L2), path to M-code
DIGAR-300   Airborne, Maritime, Ground Nulling and beamforming, STAP/SFAP, 69 in3, <5 lbs, up to 7 RF antenna inputs, 125+ dB J/S performance *, GPS (simultaneous L1 & L2), path to M-code
Small Platform AJ
  Ground, Airborne Nulling and beamforming, STAP/SFAP, 45 in3, <3 lbs, up to 7 RF antenna inputs, 95+ dB J/S performance*, GPS (simultaneous L1 & L2), path to M-code
STAP (Space Time Adaptive Processing); SFAP (Space Frequency Adaptive Processing)
* Beamsteering mode. Actual performance is classified

Situation with regards to export: All listed products are unclassified, but are subject to U.S. ITAR restrictions.

Roke Manor Research

This column wouldn’t be complete without a few words on my own organization. Roke has been developing anti-jam CRPAs since the 1980s, but rarely offers its own products. Typically Roke develops bespoke anti-jam and anti-spoof technology for other defense organizations, including for some products already listed above. Examples of bespoke developments for more specialist markets include Gincan and the Helium antenna.

Main features: Both these products are aimed at the commercial civilian market, but do also have defense interest. The Gincan is a very basic low-cost CRPA, with just two antenna elements. The Helium is a conical spiral design, using four antenna elements, and is primarily aimed at protecting GNSS in critical infrastructure. The Helium has excellent low-elevation performance. Both antennas feature very low latency, making them particularly suitable for timing receivers.

Intended market: The Gincan is primarily aimed at providing a basic level of anti-jam capability to the automotive mass market, including cars and trucks, but also has been adopted by some lightweight UAV platforms. The Helium is aimed directly at timing receivers for critical infrastructure, including mobile base stations, digital TV networks, stock exchange and financial institutions, and power and utility grids.

Example customers: Gincan has been delivered to 42 countries, with a mixture of commercial, defense and national security customers. Helium is a relatively new product, and is being trialed on infrastructure in two countries.

Situation with regards to export: Both products are unclassified and suitable for commercial use. They are subject to UK export control as dual-use items, and are ITAR-free.


There are many other suppliers of CRPA technology — unfortunately, too many to cover in this column. Mayflower Communications offer a good range of CRPA products in the form of their NavGuard range. Some other suppliers include Cobham Antenna Systems, BAE Systems Rokar, Thales, Harris Corporation, L-3 Interstate Electronics and Lockheed Martin. I encourage you to contact these companies for the latest information if you are contemplating a CRPA product. If you’re a CRPA supplier and I’ve missed you, please feel free to post a link to your products in the comments section below.

So, that was a bit of a whirlwind tour through some of the products currently around. CRPAs come in all shapes and sizes, and they all have their own particular characteristics and subtleties.

I conclude by reiterating my earlier point. Always conduct a threat analysis, seek the help of a navigation warfare expert if necessary, and properly evaluate your choices. Happy choosing!

About the Author: Michael Jones

Michael leads the Array Processing group at Roke Manor Research, where he also heads up Robust PNT technologies. His background encompasses military sensing, navigation and electronic warfare, and he has particular specialist interest in GNSS adaptive antenna systems and direction-finding technology. He gained a First-Class Master’s degree in electronic engineering with avionics from the University of York in 1999, and was awarded the Racal prize for best avionics degree.   Since joining Roke Manor Research he has worked on a multitude of advanced navigation systems for the military.  He has detailed technical knowledge of adaptive antenna GPS systems, and was jointly responsible for the development of a number of world-leading navigation protection systems utilizing interference cancellation, adaptive beamforming and direction finding. His work is in service on a variety of MoD and DoD airborne platforms around the world. He played a pivotal technical role in the ADAP programme for the U.S. military.   He specializes in the simulation, modelling and hardware implementation of advanced signal-processing algorithms, and has led a number of designs for military GNSS and navigation systems. While remaining primarily technical, he also undertakes product management, project management and business development activities.   Michael is well-known for his work, and in 2015 he was made a Fellow of the Royal Institute of Navigation in recognition of his significant and sustained contribution to the field of navigation warfare. He has published a number of papers on GNSS interference countermeasures. His current work includes robust GNSS receiver design and true anti-spoof technology.   Aside from robust GNSS receivers and adaptive antennas, Michael leads a portfolio of other advanced military navigation technologies, including visual odometry for dismounted soldiers, inertial navigation, signals-of-opportunity, eLoran and integrated navigation systems.   He is a former vice-chair of the IET’s navigation executive committee and co-chair at the International Navigation Conference. Contact him at