Active diplexer based on isolation circuits imbedded low noise amplifiers

In this paper, a novel active diplexer based on low-noise amplifiers (LNAs) using multi-functional composite right/left-handed input matching circuit (CRLH-IMC) is proposed. Since each CRLH-IMC has optimized impedance for targeted LNA performances as well as the required isolation characteristics, an active diplexer with gain and low noise figure (NF) can be realized by placing a single input port between two LNAs with CRLH-IMCs. The proposed active diplexer can reduce overall system dimension and loss by removing passive diplexer. In addition, diplexer performances such as insertion loss and isolations can now be controlled by an amplifier design. In this paper, the active diplexer prototype operating at 1.5 GHz and 2.6 GHz is designed and fabricated. The measured results show good agreement with the simulated results.