A simple design of wideband filter with miniaturized size

In this letter, a miniaturized wideband filter using step-impedance stub loaded resonator (SISLR) and longer coupling line is presented. A wide passband is first constructed using step-impedance stub loaded resonator (SISLR), by driving this SISLR with parallel coupled-line on both sides. With enhancing the source-loaded coupling, longer coupling line is adopted in this filter, thus making up a wide passband by expanding the width. The advantages of the wideband filter are simple in design and achieving a miniaturized size. Finally, a wideband filter is designed and fabricated with 78.5% fractional bandwidth which can be used to cover the UWB lower band from 3.1 to 5.15 GHz. Measured results agree well with the simulated results.