Combining method of two filtering circuits based on isolation circuits for five-channel multiplexers

This paper presents a design method of combining two multiplexers using isolation circuits such that the number of channels is increased. An isolation circuit is composed of a synthesized (metamaterial) transmission line (TL) connected to a multiplexer, while the combination of two isolation circuits has multiplexer functionality. Using this concept, the number of channels can easily be increased because the number is the sum of the channels of two isolation circuits. The freedom to choose any commercial band-pass filter or multiplexer is another positive aspect. Furthermore, it is not necessary to use a complex optimization process because of the straightforward design method. In this paper, a composite right/left-handed (CRLH) TL (having dual-band characteristics), and a double-Lorentz (DL) TL (having tri-band characteristics) are used for a five-channel multiplexer.