Multiple band rejection notches in miniaturized UWB fifth-order filter using E-shape microstrip structures

This paper, for the first time, presents a new technique to overcome the problems of realizing multiple band rejection notches in high-order miniaturized UWB filters employing the E-shape microstrip structure. The new technique employs double layer substrate where on the bottom layer the main filter is developed and on the top the circuit for band rejection notches is etched. These two filter circuits are capacitively coupled using overlapping microstrip lines. To demonstrate the technique and design process a fifth-order UWB bandpass filter is developed with two and four band rejection notches. The filter size is about 6.6 mm × 6.5 mm × 6.3 mm excluding the feeding ports.