Miniaturized dual-band bandpass filter using E-shape microstrip structure

This paper, for the first time, presents a design technique to realize a miniaturized dual-band bandpass filter based on E-shape microstrip structure for integrated wireless multi-band communication systems. The filter is patterned on a double layer substrate to achieve compact size. On the bottom layer, two E-shape microstrip structures are realized and coupled through a space gap gc to perform the specified dual passbands. The filtering response of the two passbands is improved using a top layer substrate employs two λ/4 short-circuited stubs coupled through one via hole. These two filter circuits are capacitively coupled using overlapping microstrip lines. To demonstrate the technique and design process, a multi-band bandpass filter is developed to serve a multi-communication system having center frequencies of 2.4/5.3 GHz. The filter is designed, simulated and measured. The results from the simulation and measurement show good agreement. The filter circuit size is very small about 4.24 mm × 6.76 mm × 0.63 mm excluding the feeding ports.