Wideband microstrip filters

New microstrip designs of bandpass filters have been developed on the basis of a low-pass filter with some or all of the sections of the high-impedance microstrip lines connected to a screen by stubs. The filters exhibit the high frequency selectivity and their fractional bandwidth falls within the range of 30–150%. An experimental sample filter with a passband center frequency of 2 GHz and a fractional bandwidth of 70% formed on a 1-mm-thick alumina substrate has a substrate area of 46 $\times$ 21 mm. It is shown that the measured frequency responses of the filter are in good agreement with those calculated using the numerical electrodynamic analysis of its 3D model.