Bandstop filter design using the suspended stripline structure

In this paper, the authors propose a BSF design of quasi-lumped elements realizing on the SSL structure. The building lumped elements, inductors and capacitors, are composed of various patterns of planar metallic patches which might reside on either or both sides of the SSL´s central stripline. A lumped elements circuit model is developed to analyze the prototype filter´s frequency response. The proposed BSF is built from alternatively cascading series circuit blocks and shunt circuit ones with each of the circuit blocks composing of an inductor and a capacitor. The lumped elements are in shunt-connection in the series modules and the filter´s shunt blocks have the elements in a series-connection form. Each of the circuit blocks can individually provide a transmission zero to the filter´s frequency response. A wideband BSF can be realized while multiple zero are properly arranged. The filter stopband BW is controlled by the combinations of the created transmission zeros. A wideband BSF can be realized while the multiple zeros are properly arranged. Experiments are conducted to verify the filter´s performance and good agreements are observed between the circuit model simulation and the measurements.