A Bandwidth Reconfigurable Bandpass Filter for Ultrawideband and Wideband Applications

In this brief, a reconfigurable filter is proposed for simultaneous usage as ultra-wideband and wideband filters. The ultra-wideband (UWB) section is designed by constructing three parallelly connected quarter-wavelength transmission lines with two high impedance quarter-wavelength shorted stubs. The wideband (WB) section is implemented using an open stepped impedance stub-loaded resonator (OSSLR) and a shorted stepped impedance stub-loaded resonator (SSSLR). Nine pin diodes are embedded to switch the passband from UWB to WB and vice versa configuration. The filter in UWB mode produces a passband bandwidth (
$|{\mathrm{ S}}_{11}|$
dB more than 10 dB) of 9.03 GHz from 2.15 GHz to 11.18 GHz, and the WB mode reports a passband bandwidth of 2.8 GHz, which ranges from 3.25 GHz to 6.05 GHz. Further, a lowpass filter is integrated with the design to obtain a wide upper stopband. The proposed prototype is fabricated and tested to validate the collaborative design concept. The overall circuit size of the prototype is
$0.80\lambda _{g}\,\,\mathbf {\times }\,\,0.42\lambda _{g}$
at 4.70 GHz.