Design Consideration For Composite Based Nonlinear Pulse Forming Line Systems

<p dir="ltr">Nonlinear transmission lines (NLTLs) offer pulse sharpening and high-power microwave (HPM) generation in a compact form factor. Unlike other conventional HPM devices, NLTL performance depends strongly on material properties, such as magnetic and dielectric losses, permittivity, permeability, spectral line widths, and magnetization/polarization saturation fields. Understanding the behavior of these parameters with regards to temperature and frequency is invaluable to designing NLTLs</p><p dir="ltr">Nonlinear pulse forming lines (NPFL), which are derivatives of NLTL systems, implement NLTLs in a way that reduces system size and weight while mitigating output power reduction (SWaP). Unlike traditional systems, which need a pulse forming network to drive the NLTL, the NPFL topology utilizes the line’s capacitance and treats the NLTL as both the pulse and RF source. This dissertation first focuses on material selection considerations for NPFL applications and their subsequent development. We then introduce our own ferroic and multiferroic ceramics and characterize their magnetization as functions of temperature. We extend this characterization to polymer-based composites, which provide ease of manufacturing for complex geometries and increased durability. The polymer-based composites were then implemented into coaxial NLTLs with varying impedances to understand the dependence of RF formation in the NPFL topology on system impedance. The impact of impedance on NLTL performance in this topology is then discussed.</p><p dir="ltr">Based on the results of the impedance study, we next manufactured NLTLs with exponentially tapered ferrite cores and implemented them into an NPFL system. Due to the physics driving RF formation in these systems, the tapered cores serve two roles. First, it allows the use of standardized connections, which simplifies the interconnection between supporting subsystems. Second, it provides a changing transient magnetic field, allowing for gyromagnetic precession to vary both radially and longitudinally, which increases the bandwidth compared to unform NPFL. This contrasts with traditionally driven NLTLs, which only undergo changes in the radial precession rate due to the TEM mode’s electromagnetic profile when a pulse is injected into the line. Potential drawbacks of the system are discussed along with an outline for future works.</p><p dir="ltr">Finally, we introduce alternative methods for impedance tapering using effective medium theories (EMTs), giving the designer complete autonomy over the impedance profile. A method for propagating the signal from the NPFL into free space is introduced and its drawbacks discussed.</p>