Design of a very compact and sharp bandpass diplexer with bended lines for GSM and LTE applications

Abstract

In this paper a new miniaturized bandpass-bandpass diplexer with sharp pass-band is designed and fabricated. The proposed diplexer includes two bandpass filters with sharp pass-bands. Coupling lines and stepped impedance resonators are used to form each bandpass filter. In this paper, two filters are designed in the schematic circuit mode, and then they are combined to form the final diplexer layout. After combining these bandpass filters, the transmission lines are bended to reduce the overall size of the designed filter. The operating frequencies of the designed diplexer could be selected at the desired frequencies by changing the design parameters. Proposed diplexer shows good isolation which is better than 20 dB in entire operating frequency band. Also, insertion losses in the passbands are better than 0.7 dB in output ports. The final size of the fabricated diplexer is 19.8 mm × 51.3 mm or 0.08 λ g × 0.22 λ g which shows good reduction, compared to the recent designed diplexers. The designed diplexer operates at 900 MHz and 2.6 GHz, corresponding to GSM and LTE frequencies.