A Plasma-Loaded Resonator for Integrated Filter-Limiter Applications

This article introduces a plasma-loaded resonator for integrated filter-limiter applications aimed explicitly at shielding receiver front-ends from high-power microwaves (HPMs). The innovation eliminates the need for an additional limiter circuit, thereby reducing loss and noise figures. The adaptive plasma-loaded resonator can dynamically adjust its electrical properties to the input signal’s amplitude. This adaptability is achieved by integrating a hermetically sealed plasma cell into the gap of a split-ring resonator (SRR), thereby imparting power-dependent attributes to the resonator. The theory for the adaptive plasma-loaded resonator is developed and extensively examined using circuit models. In experimental fabrication, a first-order resonator operating in the L-band is realized, exhibiting a 3-dB bandwidth of 3.1%, isolation levels surpassing 40 dB, and a passband insertion loss of 1.24 dB. The device showcases a frequency tuning range of 800 MHz (1.6–2.4 GHz) and a power threshold tuning spanning 15 dBm (from 34 to 19 dBm), with isolation exceeding 50 dB. The device also successfully operates against high-power pulsed microwaves with a pulsewidth as low as 120 ns. In addition, the quasi-absorptive nature of plasma and its nonlinearity at high powers are analyzed.