A Multi-Frequency Diplexer for the Sub-6 GHz Band

This paper proposes a microstrip diplexer network that covers the frequency bands of 0.6–0.96 GHz, 1.7–2.7 GHz, 3.3–4 GHz and 4.9–6 GHz. The diplexer is composed of the multiple matching branch and the filtering branch. Its insertion loss at lower- and middle frequencies is less than 1.5 dB, and that at upper frequency is under 2.5 dB. The diplexer achieves broadband and steep-edge filtering performances. Therefore, it can be well applied in 5G indoor distribution systems.