Miniaturized reconfigurable and switchable filter from UWB to 2.4 GHz WLAN using PIN diodes

This paper reports a new miniaturized reconfigurable and switchable filter from UWB to 2.4 GHz WLAN bands by using PIN diodes. First, a reconfigurable filter is developed which changes from bandstop to bandpass filter at the same UWB spectrum. This bandstop filter consists of two bended open stubs of quarter-wavelength and a connecting stub of half-wavelength. The bandstop filter reconfigure to bandpass filter when the two open bended stubs are shorted to ground using Avago´s RF pin diode. Different design parameters are evaluated for the reconfigurable filter. A switchable filter is developed by connecting half wavelength stub to the reconfigurable filter. This switchable bandpass filter changes from UWB to 2.4 GHz WLAN by turning ON the pin diodes. The measurement results of the reconfigurable filter in the bandstop state shows a rejection bandwidth of 2.2 GHz and the insertion loss in the passband of 1.9 dB and similarly the reconfigurable filter in the bandpass state shows the insertion loss of 2.1 dB and 3-dB bandwidth from 3.6 GHz to 10.5 GHz. The switchable bandpass filter at 2.4 GHz shows an insertion loss of 0.9 dB and 3 dB bandwidth of 400 MHz. The area of the filter is (lambda_g / 4)², while the area of the filter realized using the non bending stubs and connecting lines is 2(lambda_g / 4)².