Adjustable wideband bandstop filter with inductive coupling for ultrawideband applications

ABSTRACT In this article, we describe a miniaturized and adjustable microstrip wideband bandstop filter (BSF) with inductive coupling for ultrawideband (UWB) applications, which is fabricated on a Teflon substrate with a dielectric constant of 2.54. The simulated and measured results of the wideband BSF are determined to be in good agreement, demonstrating the 10‐dB bandwidth to be 3.78 GHz (54.8%) from 8.82 to 5.04 GHz, an insertion loss (S21) of −31.65 dB, and a minimum return loss (S11) of −0.34 dB at 6.9 GHz in the experimental results. To estimate the EM simulation results, an equivalent circuit is built for the practical realization. The advantages of the wideband BSF design are size reduction, wideband rejection, higher insertion loss, low cost, and light weight. An adjustable bandwidth can be achieved by adjusting an inner capacitive open loop for implementation in the UWB system. The physical dimension of the designed BSF occupied the size of 0.398λg × 0.316λg. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1901–1904, 2015