TECHNOLOGY AREAS: Air Platform, Sensors, Electronics, Battlespace

ACQUISITION PROGRAM: PMA-265 EA-18G Growler

OBJECTIVE: Develop a physics-based simulation tool for modeling radio frequency (RF) systems operating in dynamic and hostile environments, including effects of electromagnetic interference (EMI) and moving-part modulation.

DESCRIPTION: Tools for physics-based simulation of RF systems, such as those to predict installed antenna patterns and cosite interference, typically model a static physical environment. These include asymptotic and full-wave solvers for modeling the electromagnetic interactions of the antennas with each other and with the 3-D platform geometry, as well as RF system modeling tools that take into account the architecture of the RF devices connected to the antennas. In practice, the physical environment can change over time, sometimes rapidly, and this influences not just the final result, but also the character and domain of the result. For example, rotating propellers and fan blades are known to introduce periodic modulations in the antenna patterns for installed RF systems, resulting in additional spectra in the signal. Another example is a jamming scenario where the victim and/or the threat platforms travel on complex trajectories that influence the coupling of the jammer signal into the victim system versus time. In either case, it is desirable to predict the impact of the dynamic scenario down to the RF system level, where modulation harmonics and jammer signals are actually manifested in ways that impact the system's ability to perform its intended function. Such issues are typical of electronic warfare (EW) platforms like the EA-18G, whose intended missions include hostile environments.

A tool is required that allows analysts to accurately assess RF system performance over a time window where physical conditions change. This could be the period of a fan blade rotation or the time span of an engagement. The tool should use high-fidelity physics-based modeling to account for interactions involving moving parts of the platform(s) (or the motion of the entire platform or platforms). Use of physics-based algorithms is strongly encouraged, and the methodologies must work with arbitrary geometrical shapes and motion trajectories. In addition, the tool should be able to carry the analysis beyond the antenna terminals down to the system level metrics, such as signal to interference & noise ratio (SINR) and bit error rate (BER).

PHASE I: Demonstrate proof-of-concept prototype algorithms for solving the problems of EMI, installed antenna pattern, and other RF-system-level metrics under dynamic conditions of moving parts on platforms and also one or more platforms in complex maneuvers.

PHASE II: Further develop the proposed methods and demonstrate their accuracy, robustness, and speed. Where simulation over a time-span introduces computational bottlenecks, develop suitable algorithmic accelerations that do not unduly compromise accuracy. Incorporate these methods in a prototype tool or tool suite, including a graphical user interface (GUI).

PHASE III: Refine the methodology and tool developed in Phase II either alone or in partnership with another company to produce a commercial-grade tool that can be transitioned to the fleet.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The problems of dynamic EMI encountered on military aircraft frequently arise in commercial vehicles. A dynamic tool such as the one outlined here will find application in many industries where electromagnetic compatibility (EMC) is an issue.

REFERENCES:
1. Kodali, W.P. (2001). Electromagnetic Compatibility. New York: Wiley-IEEE.

2. Paul, C.R. (2006). Introduction to Electromagnetic Compatibility. Hoboken: Wiley-Interscience,

3. Kadar, I. (1973), An analysis of helicopter rotor modulation interference, IEEE Trans. Aerospace and Electronic Sys., vol. AES-9, No. 3, pp. 434-441.

4. Polycarpou , A. C., Balanis , C. A., and Stefanov , A. (2001), Helicopter rotor-blade modulation of antenna radiation characteristics, IEEE Trans. Antennas Propagat., vol. AP-49, no. 5, pp. 688-696.

KEYWORDS: EMI Coupling; Transmitter; Receiver; RF Performance; Electronic Survivability; Electromagnetic Interference

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