An On-chip 28/39 GHz Millimeter-wave Diplexer For 5G Dual-band Front End Modules

In this paper, a compact millimeter-wave on-chip diplexer with low loss is designed based on lumped-distributed elements. The quasi-lumped resonator consists of interdigital capacitors and inductive transmission lines with compact dimensions. The introduction of distributed electromagnetic hybrid coupling between the quasi-lumped resonators can generate two transmission zeros (TZs) on both sides of the filter passband respectively. In addition to the good isolation of the diplexer designed by connecting two different band filters with T-junctions, the isolation of the diplexer can be further enhanced by the upper stopband transmission zero of the low-frequency filter and the lower stopband transmission zero of the high-frequency filter. Finally, the simulation results of the proposed on-chip diplexer with center frequencies of 28 and 39 GHz, respectively, show that they have good performances such as low insertion loss and high selectivity.