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.