Nonlinear transmission line implemented as a combined pulse forming line and high-power microwave source

• Published in: Review of scientific instruments 2021-10, Vol.92 (10), p.104702-104702
• Main Authors: Fairbanks, Andrew J., Crawford, Travis D., Garner, Allen L.
• Format: Article
• Language: English
• Subjects: Barium strontium titanates; Charging; Electric fields; High power microwaves; Magnetic permeability; Marx generators; Oscillations; Polydimethylsiloxane; Scientific apparatus & instruments; Transmission lines
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/5.0055916

Nonlinear transmission lines (NLTLs) are typically driven by pulse forming lines (PFLs) or Marx generators to generate high repetition rate, high power microwaves (HPMs) with fewer auxiliary systems than conventional sources. This paper reports the development of an even more compact HPM system that utilizes a composite-based hybrid NLTL as the PFL and HPM generator in a single device. We designed the following three different combinations of nickel zinc ferrite (NZF) and barium strontium titanate (BST) inclusion volume loads in a polydimethylsiloxane host material to provide magnetic field dependent permeability and electric field dependent permittivity, respectively: 25% NZF, 10% BST/15% NZF, and 15% BST/10% NZF. By constructing the NLTL in a coaxial geometry, this device uses the capacitance and length of the NLTL to generate a fast rise-time high voltage pulse with microwave oscillations that occurred both during and after the pulse after exceeding a threshold charging voltage. The output frequency of the NLTLs ranged from 950 MHz to 2.2 GHz during the pulse for all volume loadings and was 1 GHz after the pulse for the 10% BST/15% NZF and 15% BST/10% NZF volume loadings. The oscillations generated after the pulse were much higher in amplitude and achieved 160 kW at a 15 kV charging voltage for the 15% BST/10% NZF composite-based NLTL.