There is much to gain in disrupting the normal operation of a GNSS receiver in the battlefield such as not allowing military platforms to determine their absolute or relative positions and messing up inter-platform time synchronization. Although with a different motivation, a similar disruption can be observed in non-military areas as well. Truck drivers trying to avoid being tracked by their company are using personal jamming devices that is also affecting timestamps on trades made in London Stock Exchange . GNSS outages reported by pilots jumped from 164 incidents in 2017 to 3,564 in 2019 due to hand held GNSS jammers, according to Eurocontrol . All these examples, and more, lead to the same very important conclusion, if GNSS jamming is perceived as a counter-measure against this powerful tool then efficient and cost effective counter-counter-measures are needed to mitigate GNSS outages caused by jamming.
In a simplified world, GNSS can be said to have two main blocks i) the antenna unit for the reception of GNSS signals, which is commonly called the front end and ii) the signal processing unit where the location information is produced. GNSS Anti Jamming can be applied at either of these levels.
Signal processing level mitigation requires access to raw GNSS signals however, this is almost impossible for legacy systems as GNSS units operate on input-output principle which means unless you are a GNSS receiver developer you cannot access any point in between input and output. Besides any technique that can be applied at this level will be effective in detecting the jamming and provide limited capability in continuing to operate. However, the key here is the uninterrupted service. Designing a GPS receiver that uses a multi-constellation and multi-frequency that is compatible to receive GNSS signals from different satellite constellations can also be considered as a signal processing level anti-jamming technique. Since it is easier to design antennas to receive signals at different frequency bands transmitted by different constellations (i.e., GPS, GLONASS, Galileo, BeiDou) and electronic filters to receive signals from these constellations, multi-constellation and multi-frequency (MCMF) receivers are widely used. This is probably the best way to mitigate unintentional jamming as one would not expect to be affected across all frequency bands by an unintentional interferer. Such a technique can also provide resilience against low-cost jammers in the case of intentional interference. However, even MCMF receivers cannot respond well to more sophisticated and more versatile jammers.
Automatic Gain Control
Automatic Gain Control (AGC) is simply a regulator that automatically controls the increase in the amplitude of an electrical signal from the original input to the output. AGC can be utilized to automatically adjust the gain of receiving GNSS antenna in order to prevent stronger jamming signals to reach the receiver. Such a technique would provide some protection against jamming but cannot guarantee the continued operation under persistent jamming.
Recently, Controlled Radiation Pattern Antennas (CRPA) are widely used with digital beamforming techniques that quickly detects the jamming direction and nulls the reception in that direction to provide resilient anti jamming capability to GNSS receivers. Employing this technique requires no access to the GNSS unit and can be applied externally to any legacy system. However, a specialized domain knowledge in digital beam control and antenna integration, which goes beyond the knowledge required to develop GNSS receivers, is needed. Assuming that the CRPA technique is adopted and offered as an integrated solution by GNSS receiver developers, still a great portion of 6.5 billion legacy systems using non-mitigated GNSS receivers cannot make use of this effective solution.
Then, equipping this most widely used positioning tool with a shield against jamming and adding resilience as an additional feature to GNSS seems to be the idea to pursue. TUALCOM has done exactly that and developed an entire Anti-Jam Family for the most trusted source for position information whether it is a legacy system or a system being developed for a specific purpose both military and non-military application.
Superior in house engineering capabilities have helped develop a state-of-the-art digital antenna control unit (DACU) to elevate the commonly used Controlled Reception Pattern Antennas (CRPA) technique for jamming suppression to another level. The proprietary DACU is easily configured to control beams of 2, 4 or 8 antennas.
While the integrated DACU-CRPA structure helps achieving Ultra-Low SWaP features the performance is never compromised providing resilience against up to 7 jamming sources. TUALCOM Anti-Jam (TUALAJ) family has the ability to work with multiple constellations and depending on the selected product, protection for up to three different GNSS bands, namely, GPS (L1, L2), GLONASS (G1, G2), Galileo (E1), and BeiDou (B1) simultaneously is provided. Each TUALAJ family member integrates easily with the existing GNSS receivers providing immediate protection. Moreover, TUALAJ family is offered with embedded GNSS receiver option for those systems with the strictest space requirements.
Now with ANTY GPS Anti-Jam device any non-military system can enjoy the same protection against jamming as their military counterparts. ANTY is a small, lightweight, low power and affordable solution for robust GNSS operation under interference. With the novel beamforming techniques developed in-house and state-of-the-art CRPA technology, ANTY outperforms its competitors ensuring GNSS availability in the presence of multiple jamming sources. Smaller than a matchbox car and weighing mere 80g, ANTY can be retrofitted to legacy systems with minimum effort, immediately increasing the availability and providing resilience. ANTY also provides a hassle free integration opportunity for new resilient GNSS system designs.
Alongside ANTY, TUALCOM offers the World’s most versatile and diverse Anti-Jam product family conforming to all size, weight, power and cost requirements.
 GPS jamming - Out of sight, https://www.economist.com/international/2013/07/27/out-of-sight, 2013.
 Jammed up: the security risks of GPS, https://espresso.economist.com/f75a5b18f76e7b0b6842b089dd91da56, 2021.