Enhancements Enabled by Multi-Element Antennas for GPS Anti-jamming Capabilities in Civil Applications

Bradford W, Parkinson, Chris Bartone

Abstract: The US Position, Navigation and Time (PNT) Advisory Board has adopted a strategy of “PTA” to ensure PNT is available for all users. The acronym stands for Protection, Toughening, and Augmentation. Elaboration can be found at (Parkinson 2022). This paper will summarize the Toughening Strategy part of the PTA and the four major techniques that a GPS receiver system can use for this purpose: 1. Signal Processing; 2. Use of Inertial Components to narrow bandwidths and enable fly-wheeling of position; 3. Controlled Reception Pattern Antennas (CRPAs - particularly digital, multi- element antennas), and 4. Satellite Enhancements such as multiple constellations, additional signals/frequencies, and increased broadcast Effective Isotropic Radiated Power (EIRP). The focus of this paper is the 3rd technique, use of CRPAs. The utilizations of multi-element GPS CRPAs have been around since the early developments of GPS. (Henderson 1980) (Euler 1984) (Hudak 1986) The US government continues to restrict the use of these multi-element antennas as part of their Export Control/International Traffic in Arms Regulations (EC/ITAR). (Title 22 Part 121 US) The recent development of high-speed, inexpensive analog to digital converters is changing the cost and availability of this toughening technique. For example, the US restriction to no more than three antenna elements is not generally honored outside the US. Internationally, existing products and companies offer 8-element and 16-element antenna array products. (Tualcom 2023) These internationally available CRPAs are multi-frequency and multi-constellations (GPS, GLONASS, BeiDou, SBAS, QZSS) Thus, these US EC/ITAR restrictions are effectively eliminating US civil manufacturers from competing and offering commercial-based products for GNSS Anti-Jam (AJ) applications. More important, these restrictions are inhibiting the applications of the GNSS AJ CRPA technologies in critical applications, such as US civil aircraft, ships, autonomous and remotely piloted vehicle (RPV) platforms. Recent research at Ohio University has quantified the value of these antennas to a GPS receiver for differing numbers of antenna elements. (Bartone 2011) This quantification is usually measured as decibels of gain in the direction of the desired (D) GPS signal minus the attenuation of the null that such antennas can present in the direction of an undesired (U) jamming source. A major purpose of the paper is to quantify the value of multi-element antennas in reducing the effectiveness against an array of six 100 Watt jammers. Several CRPA configurations are considered to illustrate the operational effectiveness in reducing the effects of jamming interference for civil applications. For example, a 20 dB improvement in gain-to-null ratio (i.e., D/U) will reduce the jammer line-of-sight area by 99%, while reducing the radius of effectiveness by 90%. This paper discusses several aspects of the current EC/ITAR regulations. The techniques have been well known for over 50 years, and the constraints are not being honored elsewhere in the world. Thus, the paper will make the case for removing these, largely inhibiting, EC/ITAR restraints and unleashing the US manufacturer’s creativity in greatly reducing the GPS jamming problem for critical civil applications.
Published in: Proceedings of the 36th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2023)
September 11 - 15, 2023
Hyatt Regency Denver
Denver, Colorado
Pages: 3731 - 3743
Cite this article: W, Bradford, Parkinson,, Bartone, Chris, "Enhancements Enabled by Multi-Element Antennas for GPS Anti-jamming Capabilities in Civil Applications," Proceedings of the 36th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2023), Denver, Colorado, September 2023, pp. 3731-3743. https://doi.org/10.33012/2023.19368
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