New Method for the Microstrip Bandstop Filter With a Wide Stopband and an Extremely High Attenuation

Abstract

A new method for the design of microstrip bandstop filter with a wide stopband and an extremely high attenuation is proposed. At the input and output ports of this bandstop filter, the tight coupling has been adopted for the coupled line with a single-ended ground. Then, a wide bandwidth and a steep slope will appear at the edge of the stopband. Moreover, two coupled bandstop-mode resonators added can result in an extremely high attenuation within the stopband. Two structures are then cascade connected. Eventually, this bandstop filter, with the attenuation of 56 dB and a fractional bandwidth of 68.4%, is developed.