A Novel Diplexer Design with Closely Situated Pass-bands for Base Stations of Mobile Communications

A novel design of diplexer for base stations of mobile communications operating within frequency bands 1710-1880/1920-2170 MHz is proposed. Diplexer is implemented on the base of inter-digital filters and it has compact design consisting of the all-metal housing including filters and coaxial power divider. The efficient combined technique for synthesis of diplexer is suggested, which is based on utilizing of coupling matrices and full-wave 3D simulation. Since the diplexer has the closely situated pass bands, the filters characteristics slope should be increased. The additional bent resonator is introduced into design to form the attenuation pole, which frequency may be tuned in accordance with specifications of diplexer. The proposed diplexer is characterized with high impedance matching and isolation (S
₁₁
<; -22 dB, S
₃₂
<; -25 dB), as well as low insertion loss (about 0.2 dB).