Bandstop filters of suspended stripline design using the quasi-lumped element approach

In this paper, bandstop filters of suspended stripline are proposed. The filters are a ladder circuit structure which has the shunt-circuit modules in the series branches and the series-circuit ones in the ladder's shunt arms. Each of these individual modules provides a transmission zero whose frequency can be independently tuned. Two bandstop filters are built from utilizing three and five of these zero-generating circuit modules, respectively. The rejection bandwidth is dominated by the distribution of the zeros. The quasi-lumped elements circuit model is developed to analyze the circuit performance and the experiments are conducted to verify the filters' design.