Design and performance analysis of a modulated patch stubbed feedline bandstop filter with dual windows tapered annular DGS

Abstract This work presents a high‐performance dual‐window tapered annular defected ground structuresdefected ground structures (DGS) based bandstop filter integrated with a modulated patch stubbed feedline. The proposed design introduces Kaiser–Chebyshev tapering coefficients with aspect‐ratio control to optimize etched annular‐ring defected ground structures. Comparative analysis with conventional uniform circular DGS highlights significant improvements in stopband bandwidth, passband ripple suppression, and rejection depth. Full-wave simulations in CST Microwave Studio followed by fabrication and vector network analyzer measurements confirm excellent agreement, demonstrating a wide stopband of approximately 6–14.5 GHz and deep attenuation levels up to 50–52 dB. The integration of nonuniform annular-ring tapering and stubbed feedline geometry effectively enhances impedance matching, minimizes fabrication-induced ripple, and enables superior performance over existing filters. These results indicate the proposed structure’s suitability for GHz-range applications such as wideband planar antennas, reflectors, amplifiers, and advanced microwave imaging systems.