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Clean Electromagnetic Environment (EME) Generation

Description:

TECHNOLOGY AREAS: Sensors, Electronics

OBJECTIVE: The contractor shall develop a methodology to greatly reduce the occurrence or magnitude of intermodulation products in an RF environment generation system.

DESCRIPTION: The US Army Electronic Proving Ground (EPG) is the Army’s Developmental Tester for tactical electronic warfare (EW) systems. The Army needs these EW systems to be able to operate effectively in very dense and complex Radio Frequency (RF) Environments. In our testing we often are tasked to generate a tailored Electromagnetic Environment (EME) specific to the area of interest for the System Under Test (SUT) or to play out a specific operational scenario. Some scenarios are so specific that a set of signals and protocols, must be transmitted in the correct sequence with the exact content in order to test an SUT. These special signal sets may be transmitted with additional environment signals or they may be in a more benign environment. Often EPG’s goal is to develop a valid signal script for the SUT or area of operation and faithfully transmit this script over the air to immerse the SUT in this desired environment. A natural consequence of generating many signals within a simulator system and then transmitting them through a common amplifier and antenna system is that intermodulation products are produced. These intermodulation products are extraneous, unwanted signals with no universal method to remove them. They take up a percentage of the amplifier’s power. present extraneous signals to the SUT that were not called for in the test, or occur in unauthorized frequencies. One method to partially reduce these unwanted signals is to use higher power output amplifiers but that comes with a much higher price along with increased power draw and cooling requirement.  Both of which limits our ability to field EME generation systems.

The goal of this project is to develop a methodology to analyze the signal scripts as a time ordered event list and by knowing which signals are present simultaneously, estimate the intermodulation products that would be produced. Then provide a methodology to greatly reduce or eliminate each of the intermodulation products before it can exit the amplifier. Does knowing the intermodulation products ahead of time give us an opportunity to be able to cancel them out within the amplifier before they are amplified and transmitted? If we did not have a time ordered event list and the mix of signals transmitted were a freeplay scenario of random signals is there a way of stopping these intermodulation products from complicating our transmissions, amplifiers, and environment?

Typical amplifier band breaks for our EME systems would be:

1 – 30 MHz

20 – 500 MHz

500 – 1000 MHz

1000 – 3000 MHz

The successful methodology would allow for quicker EME scenario generation without requiring extensive test equipment to confirm the quality of the environment to be presented. On site operators could use this tool to modify test sequences with less risk involved in producing a poor quality script.  In addition it is anticipated that existing test equipment will be use in a larger set of scenarios minimizing the equipment that needs to be supported and fielded for testing.

Although the testing example described here is a rather specialized case EME generation is becoming common in many testing and training applications.  EPG also tests tactical radio frequency (RF) networks and their performance in dense urban environments is also an issue.  Many urban training sites have been built in the last decade and primary component of the environment is the electromagnetic environment.  The training takes in to account the inability to communicate as hostilities escalate so does the use of the RF spectrum and good communications deteriorate just as they are needed most.  One of the biggest investments in an urban setting is the Army’s Brigade Combat Team Modernization (BCTM) program is setting up EME generation systems for that training site.  Thus numerous opportunities exist in creating EME systems for government testing and training organizations.  In the commercial sector the manufacturers of automobiles, aircrafts, ships etc also expose their vehicles to high powered signals and also to dense environments to ensure their control systems are shielded well enough to survive these environments.  Again numerous opportunities exist for this technology to greatly reduce costs in the makeup of the EME generation systems.  A technology that could reduce or eliminate intermodulation produces would reduce the RF amplifier costs, operation, maintenance, and cooling costs of the entire system.

PHASE I: Determine the technical feasibility for a methodology to eliminate or greatly reduce the magnitude of intermodulation products from signals mixing in an active RF device. Provide a clear path to accomplish this methodology in an automated manner. Show analysis or modeling that proves the viability of the methodology.

PHASE II: Develop the methodology in its automated form to a prototype or proof of concept level for demonstration purposes. By the end of Phase II provide a demonstration of the desired performance enhancement of the methodology to the Government and deliver a final report on all plans and results.

PHASE III: The intention for Phase III is to procure a production ready capability based upon the successful demonstration of Phase II. The form of this capability is unknown at this time but expected to be readily adaptable to existing RF amplifiers and current EPG test operations. There will be many other Government customers for this technology to increase the fidelity and reduce the cost of their own EME generation which has become a backdrop to all manner of test items. This would also benefit military electronic countermeasure systems, Electronic Attack, (EA) to be more efficient and more precise in the target frequency bands. The technology would be adaptable to the next generation EA systems that attempt to surgically target specific signals rather than utilize a wide band barrage of noise. The surgical method would transmit several narrow band signals, each to counter a specific target and this technology would avoid the creation of numerous unintended intermods that parasitically drain power from the intended targets and may unintentionally jam the friendly signals. Commercial applications for this technology would include broadband amplifier manufacturers and manufacturers of multichannel communications systems.

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