UWB bandpass filter with notched band using broadside-coupled microstrip-coplanar waveguide structure

In this paper, a novel and compact ultra-wideband (UWB) bandpass filter with a narrow notched band in the UWB passband using broadside-coupled microstrip-coplanar waveguide (CPW) structure is presented. To avoid the interference with the WLAN system, the operation band centered at 5.8 GHz (5.725-5.825 GHz) is notched by embedding open stubs in the microstrip lines. The resonances of stubs introduce a narrow rejection band in the UWB passband. Another two symmetric open stubs are etched on the feed lines to improve the property of the upper-stopband. The filter prototype is optimized and fabricated to demonstrate the notch-band-included and upper-stopband-improved UWB bandpass performances. Good agreement is found between the simulated and measured results.