Design and Characterization of Broadband Triplexers

This paper presents the design process of broadband diplexers and triplexers realized in suspended stripline technology on a 203 μ m thick Rogers 4003C substrate in the microwave frequency range. The design of the multiplexers is based on equivalent circuit models for the low-pass and band-pass filter separately. Stepped-impedance filters and coupled-resonator filters are used as low-pass and band-pass. A realized diplexer features a return loss of more than 10dB from DC to 17GHz with low channel insertion losses of typically less than 2dB after proper optimization. A first prototype triplexer clarifies the challenges and demonstrates the feasibility of the design process.