Theory and Design of Frequency-Selective Absorptive Plasma Limiters
Sandeep Narasapura Ramesh, Abbas Semnani
Abstract
A novel plasma-based frequency-selective limiter (FSL) technology is introduced in this article, which integrates an absorptive bandstop filter topology with a plasma coupling structure. Specifically, the design includes two signal paths: one through a delay line and the other one through two coupled resonators with a plasma cell within their interresonator coupling structure. It is designed so that when plasma ignites under high input powers, the two signals destructively interfere at the resonant frequency, yielding a selective bandstop response. Conversely, they constructively add, producing an all-pass response when the power level is low and the plasma cell is OFF. The theory of this novel plasma FSL is developed and comprehensively evaluated using coupled transmission line theory. The fabricated prototype in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -band demonstrates measured 10-dB bandwidth of <2.7% (high selectivity), isolation of over 60 dB, and an insertion loss of 1.5 dB. The design allows for a 600-MHz (2.15–1.55 GHz) frequency tuning and threshold power tunability of 19 dBm (36–17 dBm). Furthermore, the limiter has a response time of less than 10 ns and excellent linearity performance with an IIP3 of +51.5 dBm. These results demonstrate the superior effectiveness of this limiter against high-power microwave tones.