Compact microstrip diplexer using new design of triangular open loop resonator for 4G wireless communication systems

A compact microstrip diplexer for 4G wireless communication systems is proposed in this paper. This diplexer consists of two bandpass filters based on the triangular open loop asymmetric stepped impedance resonator in order to have a small size as well as simple structure. The T-shaped open stub is used for attenuating the undesired modes. Attenuation level for the proposed diplexer is less than 21 dB in the range of 0–10 GHz owing to using this T-shaped open stub. The center frequency of each filter can easily change in the range of 20 MHz through varying the gap length of the resonator without any changes in the whole structure of the diplexer. The result of this is the stability of other parameters like insertion loss, return loss and isolation. This diplexer has a narrow band frequency response that makes it suitable for modern wireless communication systems. Finally, the diplexer is fabricated at 2.30 and 2.55 GHz and measurements demonstrate a good agreement between simulated and fabricated diplexer.