Development of Wideband Microstrip Bandpass Filter Involved Defected Ground Structure

Many techniques have been used to improve filter performances deployed using microstrip technology. One of them is by involving defected ground structure (DGS) into the structure of microwave filter. In this paper, a wideband microstrip bandpass filter (BPF) is developed using a combination of two kinds of DGS for bandwidth improvement. The DGS consists of four rectangular slots and a rectangular ring slot which are incorporated at the groundplane on the bottom side of filter. The proposed microstrip BPF configured by four elements with tapered feeding lines is designed and fabricated on an FR4 epoxy dielectric substrate. From the characterization result, the realized microstrip BPF with DGS which has a compact size of of 27.4 mm × 22 mm could produce the working bandwidth of 4.097 GHz in the frequency range from 1.472 GHz to 5.569 GHz.