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Description
Nonlinear transmission lines (NLTLs) utilize nonlinear dielectrics to sharpen the input pulse to generate an electromagnetic shockwave for compact, high repetition rate, high power microwave sources. This shock wave generates microwave oscillations that can be propagated as a directed beam toward the intended target. Materials such as barium titanate (BT), barium strontium titanate (BST), and nickel zinc ferrites (NZF) have been used in NLTLs for their nonlinear dielectric or magnetic properties. Alternatively, one may adjust a composite’s effective bulk parameters by adding inclusions of different permittivity, conductivity, or permeability. For instance, adding 2-3% of stainless steel fibers to a plastic makes the composite resemble stainless steel electrically for electromagnetic shielding [1]. Others have evaluated the dielectric properties of composites using nickel zinc ferrites coated in BT in a ceramic base medium for high energy density capacitors. The BT coated ferrite composite has a higher permittivity and lower magnetic loss than a bare ferrite composite [2].
This study evaluates the permittivity of composites comprised of various volume loadings of BST, the permeability of composites comprised of various volume loadings of NZF, and the permittivity and permeability of materials comprised of inclusions of both materials. Measurement system development for measuring nonlinear permittivity and permeability at microwave frequencies will also be discussed.
This material is based upon work supported by the Office of Naval Research under Grant No. N000014-18-1-2341.
References
[1] A. L. Garner, W. Lafayette, G. J. Parker, and D. L. Simone, “A Semi-Empirical Approach for Predicting the Performance of Multiphase Composites at Microwave Frequencies,” IEEE Trans. Dielectr. Electr. Insul., vol. 23, pp. 1126–1134, 2016.
[2] R. Curry, A. Pearson, K. Noel, and S. Mounter, “Development of Metamaterial Composites for Compact High Power Microwave Systems and Antennas,” Columbia, MO, 2016.
