Simulation of shock waves in ferrite-loaded coaxial transmission lines with axial bias

Abstract

A novel model is presented for shock wave development in axially-biased ferrite-loaded coaxial lines. The one-dimensional transverse electromagnetic plane wave equations for the coaxial line are linked to the three-dimensional Landau-Gilbert gyromagnetic equation describing the coherent ferrite magnetization process. The effects of demagnetization field terms imposed by the ferrite and coaxial line geometry are identified. Numerical time-stepping solution gives the predicted transmission line waveforms directly in the time domain. Simulated and experimental waveforms are compared for a nickel-zinc ferrite-loaded coaxial pulse-sharpening line. The model is shown to give generally good results for the shock front waveform, rise time and propagation characteristics, except that predicted and measured rise times diverge increasingly at very low pulse amplitudes.

Exciting High Frequency Oscillations in a Coaxial Transmission Line with a Magnetized Ferrite

“…The great majority of previous papers on the subject (e.g., [3][4][5]8]) made use of the simple model where the electromagnetic pulse in the ferrite retained the initial modal structure of a TEM wave, as supported by the 'empty' TL1 line. Equations (1) and (5), with and , and involving the only non-zero field components E ρ , E φ and H z , then could be recast to familiar telegraph equations that govern the voltage and current in the coaxial line conductors, and the magnetic flux through the cross-section plane [2][3][4].…”

“…Equations (1) and (5), with and , and involving the only non-zero field components E ρ , E φ and H z , then could be recast to familiar telegraph equations that govern the voltage and current in the coaxial line conductors, and the magnetic flux through the cross-section plane [2][3][4]. These, in turn, could be brought to a second-order differential equation for the current I through the line (alternatively, voltage), viz.…”

“…Obviously enough, this approach does not allow analyzing variations of the electromagnetic field along the coordinates transverse to the propagation direction, z, similarly as it ignores polarization of the field, while making account of the ferrite's non-linear response. Dolan's paper [3] was among the best physically grounded 1D analyses of pulse propagation through the NLTL, yet its account of the effective field in the ferrite (in terms of classic demagnetizing factors) seemed to be fully empirical rather than self-consistent (and, apparently, remained within a linear approximation). The corresponding estimates for h ρ , h φ and h z were…”

“…The non-linear effects accompanying propagation of pulsed electric currents through a transmission line partially filled with a ferro-or ferrimagnetic material have been studied since early 1960s [1][2][3][4][5][6][7][8], first in connection with pulse sharpening and formation of electromagnetic shocks [1,2]. Today, the attention of researchers has shifted toward direct conversion of the short video pulse into radio frequency (rf) electromagnetic oscillations which can be extracted from the generating structure in the form of high power pulsed radiation [3][4][5][6][7][8].…”

“…Today, the attention of researchers has shifted toward direct conversion of the short video pulse into radio frequency (rf) electromagnetic oscillations which can be extracted from the generating structure in the form of high power pulsed radiation [3][4][5][6][7][8]. High power electromagnetic pulses of nanosecond duration prove useful in a variety of applications, such as digital data transmission, energy transfer, radar or medical/ biological research [9].…”