Development of Dual-Band Microstrip Bandpass Filter Based on Dual-Mode Resonator for Wireless Communication Applications

This paper discusses the development of a dual-band microstrip bandpass filter (BPF) based on a dual-mode resonator implemented for wireless communication application. The proposed microstrip BPF is targeted to work at two frequency bands with the center frequencies of 1.575 GHz for Global Positioning System (GPS) L1 and 2.45 GHz for Wireless Local Area Network (WLAN) communication applications. The filter is configured by two dual-mode resonators and two feed lines with each shape takes an imperfect ellipse. A 1.6 mm thick FR4 epoxy dielectric substrate with the dimensions of $\mathbf{6 8. 6} \mathbf{~ m m}$ $\times 37.2 \mathrm{~mm}$ is used for the design and realization. The optimized design is then realized for experimental measurement. The measured results of realized dual-band microstrip BPF have two frequency band responses, the first is at the center frequency of 1.575 GHz with the reflection coefficient ($S_{11}$) and transmission coefficient $\left(S_{21}\right)$ values of $-\mathbf{2 0. 9 6 9} \mathrm{dB}$ and -2.693 dB respectively, and the second is at the frequency of 2.525 GHz with the $S_{11}$ and $S_{21}$ values of -16.617 dB and -2.483 dB, respectively.