Microstrip dual-band dual-path bandpass filter

A dual-mode dual-band bandpass filter topology is proposed by connecting two quarter-wavelength parallel coupled-lines to two half-wavelength lines creating a dual-path structure. Based on the topology, the characteristics of the filter response such as the bandwidth and the separation between the bands can be controlled by varying the even- and odd-mode impedances of the coupled-lines and the line impedance of the half-wavelength lines. Using microstrip technology, the filter was designed at 2.5 GHz using TRF45 (Taconic) and the results show the filter is suitable in addressing medium band applications. These concepts are validated through simulations and experiments.