Microstrip Filters Based on Open Stubs and Sir for High Frequency and Ultra-Wideband Applications

Abstract

This paper includes two new microstrip filter configurations for high frequency and ultra-wideband applications. The first proposed filter is a composition of four parallel open-circuited stubs connected by optimized fractal-structured microstrip line. The filter response is a combination of three passing regions, namely, low pass from 0.1 GHz to 3 GHz, band-pass from 4.5 GHz to 9 GHz, and high pass from 10.5 GHz to 13 GHz, separated by two rejection regions from 3 GHz to 4.5 GHz and 9 GHz to 10.5 GHz. Deep and sharp rejection regions reaching up to-44.6 dB with 40 % fractional bandwidth (FBW) are observed with a good electrical performance. Furthermore, with a comparative table, the advantages of this proposed BSF in terms of FBW, compactness, and insertion loss are compared with recently reported related studies. Secondly, a dual -band band-pass filter implementing a stepped-impedance resonator (SIR) and a modified H-shaped structure is presented. This filter is designed to operate in a low pass region up to 3.58 GHz and a band-pass region from 15.38 to 21.65 GHz, with a wide stopband region between 4.46 and 14.07 GHz. The simulated and measured results are in good agreement. Compared to its peers, the compact size and low price allow for a wide application of these filter configurations, while passing frequencies allow operation in the unlicensed frequency spectrum, which is popular for high-speed communication.