High Power Microwave Frequency Selective Surfaces

In general, there are two ways an FSS Radome subjected to an HPM source can fail. The first is under a sustained continuous high average power signal where heating in lossy materials causes melting or burning. The second is under a very high peak power signal where arching or breakdown occurs within or around the FSS elements, essentially shorting them out. During the Phase I of this SBIR, novel designs were investigated for an L-band radome that could withstand the latter of the two signal types. For this investigation a combination of FSS element shaping and high dielectric materials was used to increase the power handling capability of the radome. Detailed CEM analysis was performed during this phase which provided precise knowledge of the field strengths throughout the radome. During the Phase II effort, these same CEM tools will be used to optimize the Phase I design, whereupon a test coupon will be fabricated for the purpose of demonstrating the electrical properties at low power. Having confirmed the electrical properties and mitigated the highest risk elements of the design, a high power proof of principle experiment will be designed and executed in order to demonstrate the power handling capability. BENEFIT: There are two primary anticipated benefits to the HPM FSS radome being proposed here. The first and most obvious benefit is the protection the band-stop radome affords the HPM antenna. While the HPM FSS radome appears transparent within the band of operation of the HPM antenna, outside of this band it appears opaque. Therefore, if confronted by an adversarial HPM the proposed radome will block any harmful HPM signals that are not in its own operational band. The second anticipated benefit of the proposed HPM radome is that the design can easily be modified to generate its complimentary band-stop counterpart. By merely replacing the slot FSS with its dipole counterpart the FSS radome becomes opaque instead of transparent at the operational frequency of the HPM source. For an HPM source located on a platform populated with other antenna systems this band-stop radome would provide protection for these antennas against the neighboring HPM source. Commercial applications include the HPM hardening of critical computer network systems. As the technology in HPM progresses, HPM sources will continue to get smaller and cheaper, eventually making it conceivable for non-military personnel to acquire these weapons. The band-stop variant of the proposed radome could be used to protect otherwise vulnerable computer networks and databases whose disruption in many cases could have a worldwide impact.