GHz selective filter based on a transmission line with an RHM/ENG resonator and metamaterial absorber

Abstract

Abstract In this article, we investigate the propagation of electromagnetic waves (EW) within a different type of transmission line, combining a theoretical analysis based on the Transfer Matrix Method (TMM) and a numerical study based on the Finite Element Method (FEM). The proposed structure is composed of a segment filled with a right-handed material (RHM, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mspace width="0.25em"/> <mml:mi>ε</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msub> </mml:math> &gt; 0 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mspace width="0.25em"/> <mml:mi>μ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msub> </mml:math> &gt; 0), coupled to a closed lateral transmission line resonator filled with a metamaterial ENG, RHM or an absorber with effective permittivity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>ε</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:mi>f</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mspace width="0.25em"/> <mml:mi>μ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> &gt; 0). The transmission line resonator is modeled as a microwave circuit with lumped elements, including a series capacitor (C), a shunt inductor (L), and a resistor (R). The results demonstrate that adjusting the resonator length and its electrical parameters allows multiple transmission bands over a wide frequency range (up to 10 GHz), while finely controlling the reflection and absorption characteristics, resulting in very narrow resonance modes. These features make the proposed structure suitable as an integrated gigahertz selective filter for optimized filtering in advanced signal processing, telecommunications, radar, and satellite applications.