All solid-state high power microwave source with high repetition frequency

Abstract

An all solid-state, megawatt-class high power microwave system featuring a silicon carbide (SiC) photoconductive semiconductor switch (PCSS) and a ferrimagnetic-based, coaxial nonlinear transmission line (NLTL) is presented. A 1.62 cm(2), 50 kV 4H-SiC PCSS is hard-switched to produce electrical pulses with 7 ns full width-half max (FWHM) pulse widths at 2 ns risetimes in single shot and burst-mode operation. The PCSS resistance drops to sub-ohm when illuminated with approximately 3 mJ of laser energy at 355 nm (tripled Nd:YAG) in a single pulse. Utilizing a fiber optic based optical delivery system, a laser pulse train of four 7 ns (FWHM) signals was generated at 65 MHz repetition frequency. The resulting electrical pulse train from the PCSS closely follows the optical input and is utilized to feed the NLTL generating microwave pulses with a base microwave-frequency of about 2.1 GHz at 65 MHz pulse repetition frequency (prf). Under typical experimental conditions, the NLTL produces sharpened output risetimes of 120 ps and microwave oscillations at 2-4 GHz that are generated due to damped gyromagnetic precession of the ferrimagnetic material's axially pre-biased magnetic moments. The complete system is discussed in detail with its output matched into 50 Ω, and results covering MHz-prf in burst-mode operation as well as frequency agility in single shot operation are discussed.

Spatially Dispersive Ferrite Nonlinear Transmission Line With Axial Bias

“…The NLTLs make use of a nonlinear material, such as nonlinear dielectrics, semiconductors, or ferrite as the nonlinear medium [1]- [10]. If a high voltage pulse is injected into a transmission line containing ferrite, a shock is formed at the leading edge of the pulse.…”

“…Due to the hysteresis in the ferrite, after this initial shock, the transmission line is linear and signals riding on the pump pulse behind the shock propagate on a linear circuit [2]- [6]. Coaxial ferrite filled NLTLs using an external axial magnetic bias field have been called gyromagnetic oscillators if they derive the RF generation from damped gyromagnetic precession of ferrite domains subject to a rapid change in the direction of the external field [7]- [10]. The NLTLs which derive the operating frequency from the phase matching of a shock front with a slow RF wave have been labeled as synchronous wave NLTLs [3]- [6].…”

RF pulse formation dynamics in gyromagnetic nonlinear transmission lines

“…The shock wave velocity is changed with the bias magnetic field which is a basis for multichannel NLTL systems with a bias control of phase in each channel [7][8].…”

“…Optimal conditions are found for the generation of rf pulses with frequencies from 0.6 GHz [1] to 5 GHz [5], rf power from tens MW [4] to several hundred MW [2], pulse repetition rate from 800 Hz [6] to 65 MHz [7]. Based on these studies, multichannel rf sources with electronically controlled beam steering are designed and investigated [8][9].…”

A compact two-way high-power microwave combiner

“…[1][2][3][4] Based on the limited power capacity of the HPM sources, the HPM combinations were proposed to further improve the output power. 3 The HPM combination in waveguides and by sharing the same output horn has the advantage in controlling the space radiation, and preventing the spatial disturbance among the array antennas from multiseparated HPM sources.…”