Planar wideband band-stop filter with T-inverted shaped open stubs for wideband applications

Abstract

This paper presents a wideband band-stop filter (BSF) structure designed by using planar technology. The proposed filter consists of a modified conventional band-stop structure with open stubs, inner T-inverted shape, and two input/output feed lines. Based on series of optimization and a specific design method, two compact filters with good electrical performance are obtained. In order to characterize the frequency response of the proposed filters, the performance is carried out numerically using two different solvers (Advanced Design System -Momentum and CST-MWS). Furthermore, in order to validate the conception approach, two circuits are designed, fabricated, and tested. Additionally, an equivalent circuit of the wideband BSF is built to estimate the electromagnetic simulation results for practical realization. The features of the design have a reduced size, wideband rejection, and higher insertion losses, which can be performed by adjusting the L-shaped stubs (23.25 × 2.2 mm2) toward the 50 Ω input and output ports. Two filters are designed, fabricated, and tested; one can be operated between an fractional bandwidth (FBW) of about 50% at a center frequency of 1.8 GHz, and the other can be switched from an FBW of 43.38% at a center frequency of 1.82 GHz. In addition, good agreement between the simulation and the measured results is achieved. The overall size of each filter is 43.4 × 34.5 mm2.