Electronically switchable ultra-wide band/dual-band bandpass filter using defected ground structures

Abstract

In this paper, an electronically switchable ultra-wideband (UWB)/dual-band bandpass filter using defected ground structures (DGSs) is proposed. The proposed filter consists of meandered inter-digital coupled line sections, stepped impedance open stubs, coupled lines, and rectangular DGSs to realize high performance in the operation band with a compact size of 12.5mm × 10mm. The proposed filter is designed on an RT/Teflon substrate (εr = 2.2, h = 0.7874mm). The main advantage of the proposed filter is the reconfiguration of ultra-wide bandpass filter to dual-band bandpass filter. UWB has passband from 3.6GHz to 10.6GHz with upper wide stopband attenuation better than 20 dB up to 18 GHz. The dual passbands extend from 3.8GHz to 5GHz and from 9.5 GHz to 10.8GHz. This filter is able to provide interference immunity from unwanted radio signals, such as wireless local area networks (WLAN), worldwide interoperability for microwave access (WIMAX) that cohabit within the UWB spectrum and X (Military) band of satellite from 7 GHz to 8 GHz. The state of filter can be changed by using switching matrix equipment (mini circuit, replacement of PIN diodes). To validate the design theory, an electronically switchable UWB/dual-band bandpass filter using DGSs is designed, fabricated, and measured. Good agreement is found between simulated and measured results.