A Bandpass Filtering Approach Using Commensurate Transmission Lines

Abstract

This paper presents a design approach for a broadband bandpass filter suitable for X Band (8-12 GHz) applications. The proposed filter design combines a fifth-order step line filter with a third-order bandpass filter. The step line filter, synthesized using the lowpass Synthesis MATLAB Tool based on Simplified Real Frequency Techniques (SRFT) in the Richards Domain, employs commensurate transmission lines. To address periodicity issues resulting from Richards Synthesis, a novel approach is introduced by adding a coarse third-order bandpass filter to the step line filter. This approach enables the realization of compact and robust bandpass filters compared to conventional designs. Schematic and layout designs are completed via Advanced Design System (ADS). Simulations demonstrate that the filter exhibit maximum 1 dB Insertion Loss Ripple (ILR) and 30 dB Insertion Loss (IL) at stopbands. © 2023 IEEE.