▎ 摘　　要

Bandpass diplexer (BPD) has been widely used to provide sufficient bandwidth (BW) for transmitter and receiver in smart frequency-division duplex (FDD) system in recent years. In this letter, graphene, as a carbon-based nanomaterial, is used as a lossy role in a BPD because of its tunable resistance peculiarity. While the electric field strength of the resonator reaches its maximum, the graphene flakes placed around the resonator will absorb the accumulated electric field, thus achieving maximum attenuation. Additionally, with the varying of the bias voltage added to the graphene flakes, the square resistance will alter linearly as well, resulting in different degrees of attenuation. Consequently, a 1.4-2.4-GHz graphene-based BPD with nearly 150-200-MHz BWs is simulated, fabricated and measured. As the bias voltage increases from 0 V to 6 V, attenuation can be tuned from 3 dB to 10 dB while remains a low reflection (S11 < -10 dB).