Miniaturized reconfigurable filter using PIN diode for UWB applications

This paper reports a new compact design of UWB reconfigurable filter which switches from bandstop to bandpass filter using pin-diode. First, a unit cell is developed which consist of two bended open stubs of quarter-wavelength and a connecting stub of half-wavelength. Two unit cells are cascaded by inductive stub to form a bandstop filter. Avagopsilas RF pin diode is used to switch the filter from bandstop to bandpass filter at the same resonant frequency. The equivalent circuit model and its parameters are extracted. The measurement results for bandstop filter shows a rejection bandwidth is 5.2 GHz and the insertion loss in the passband is 0.6 dB. For the bandpass filter, the insertion loss is 2.1 dB and 3-dB bandwidth is from 3.6 GHz to 10.5 GHz. The area of novel unit cell filter is ( lambda_g/4)² at the centre frequency of the bandstop, while the area of the filter realized using the non bending stubs and connecting lines is 2( lambda_g/4)² for the same bandstop characteristics.