Analysis of Dual Band-Reject Filter Unit Cell Based on Miller Loading Effect using Strongly Coupled Parallel Lines

Abstract

This paper presents the analysis of a novel unit cell of a dual-band reject filter. This unit cell is proposed by using the Miller loading effect on the band-pass filter. The bandpass filter used in this model is designed from parallel coupled lines. Miller loading effect is used in electronics to change the equivalent impedance at input and output ports by connecting an impedance between the input and output ports. This change in the equivalent impedance at input and output alters the resonant frequencies of the band-pass filter and makes it a dual band-reject filter depending on the nature of impedance that has been connected between the ports. Theoretical and numerical simulations is carried out on circuit models with normalized impedances and normalized resonant frequencies. To validate theoretical and numerical simulations, a microstrip bandpass filter based on parallel coupled lines has been converted into a dual band-reject filter. Full-wave electromagnetic simulations are performed and these simulation results are in good agreement with the theoretical and numerical simulations.