Frequency Division Multiplexing In LCP Multilayer Circuits

With the rapid development of wireless communication technology,communication services and user numbers continue to grow rapidly,and thus spectrum scarcity has become a global issue.To address this,communication spectra have to be pushed towards the higherfrequency millimeter wave band,and more efficient spectrum allocation techniques must be adopted.Frequency division multiplexing(FDM)is a classical multiplexing technique that has been widely used in communication fields such as base stations and satellite relays.The use of directional filters to design FDM has the advantages of simple design,modularity,and little reflection.However,it is limited by the performance of the current directional filters,which cannot achieve high-frequency,small-scale,broadband,and low-loss performances.In light of this,this paper proposes a broadband directional filter and its FDM on LCP multilayer circuits.The specific research outcomes of this paper are as follows:1.A broadband directional filter based on LCP multi-layer circuits is proposed.Based on the design method of the dual-slot directional coupler and traveling wave loop directional filter,the structure of the dual-slot directional filter was designed in a three-layer circuit with LCP as the substrate.The S-parameter transmission of multi-loop cascaded multilayer directional filters was analyzed,and broadband directional filters of both identical-frequency and differentfrequency multi-loop cascades were designed.The relevant parameters of bandwidth performance were analyzed and optimized,achieving a broad relative bandwidth of 14.4%at 95 GHz and low insertion loss of 2.6 dB.The reflection of the filter is lower than-10 dB in the range of 70 to 110 GHz,the size of the proposed device is as small as 1.3 mm × 6 mm.The designed results were processed and tested on multilayer samples using the LCP multilayer bonding and compression process,and the final measurement results are in good agreement with the simulation data.3.A frequency division multiplexer based on multilayer directional filters is proposed.The proposed frequency division multiplexer operating at E-and W-band is designed using a multilayer circuit directional filter cascading scheme.Three dual-loop cascaded directional filters at the three frequencies were designed,and the corresponding insertion losses were 2.28,2.49,and 2.6 dB,respectively.The cascading parameters in the multiplexer were theoretically analyzed and optimized by simulation,and limit of channel spectrum interval and isolation performance of the design were investigated.The 3-dB bandwidth of each channel at 74,84,and 94 GHz is 8.2%,8.5%,and 8.7%,and the insertion losses are 3.5,3.36,and 2.65 dB,respectively.The spectrum interval between the adj acent 3-dB bandwidths is as small as 0.14%of the center frequency,and the center frequency interval was 6.76%,revealing excellent spectrum interval and isolation performance with the device size as small as 13 mm × 3 mm.The proposed device was subjected to multilayer sample processing testing,and the final measurement results of the fabricated device are consistent with the simulation data.