Design of a Compact ‘t’ Shaped Dual-Band Bandstop Filter using Parallel Coupled Lines

In this paper, a 't' shaped dual- and bandstop filter employing parallel coupled lines is proposed. The filter topology consists shunt connected parallel coupled lines with electrical lengths of 90º and 270º. The shunt connected coupled lines provide two paths for the incoming signal. The signals propagated through these two paths interact at the output port and thus create passbands and stopbands. The combination of shunt 90º and 270º coupled lines provides a second order dual-band bandstop filter with seven transmission poles. The proposed filter is realized on AD250C substrate using Ansys HFSS full-wave simulator. The two stopbands are centered at 0.9 GHz and 2.4 GHz and their 10 dB fractional bandwidths are 55.2% and 13.3%, respectively.