Wideband Bandstop Filter Design With High Impedance Folded Stubs

This proposed structure of Wideband Bandstop Filter has stub topology, consists of high impedance folded multiple stubs, which controls Skirt Factor and band stop range. The response of the filter can be controlled by the length, width and space between stubs, and folded stubs can control capacity of storing power between two stubs. This structure of filter has cut-off frequency of 2.14 GHz. Further, for validation of response of the filter, the transmission line model is extracted. The stopband rejection level can be controlled by stubs width, stubs length and spacing between stubs. Three Transmission Zeros (TZ) are present in rejection band region. This proposed filter has 2.14 GHz −4.26 GHz band width with greater than 18.5 dB rejection over the entire stopband range. The Skirt factor is achieved 135dB per GHz. The proposed structure has compact size of
$15.5\text{mm}\times 35.8\text{mm}(0.15\lambda \mathrm{g}\times 0.35\lambda \mathrm{g})$
with port length.