Design Of 5G High Performance Filter Device Based On LTCC Technology

With the development and progress of industrial technology,wireless communication has entered the 5G era.LTCC low temperature co-fired ceramic filters have gradually become mainstream due to their low insertion loss,miniaturization,low cost,and easy three-dimensional integration.This paper uses LTCC technology to conduct research on 5G high-performance filters.The main contents are as follows:(1)Lumped-parameter filter design.The network synthesis method is mainly used to construct the equivalent circuit of the corresponding filter,and then the appropriate inductor-capacitor structure is selected to model the flexible layout of the components and efficiently implement the filter design.The designed low-pass filter has a cut-off frequency of 500 MHz.It uses a two-order LC parallel resonant structure to achieve low insertion loss at a low order.At the same time,two transmission zeros are introduced in the near-end stopband to form a steep sideband.High impedance is achieved with fewer components.With suppression,the size is1.25×2.0×0.95 mm,which has been used in the front-end circuit of a chip of NB-Iot;The designed bandpass filter uses a third-order resonant coupling structure with an insertion loss of better than 1.2d B.The source-load coupling structure is used to introduce transmission zeros in the low-frequency stopband to improve low-frequency rejection.Creatively propose three layers of defect ground and through-hole pillars."Second Resonance" structure,introduces zeros around 12 GHz,effectively suppresses second and third harmonics,and achieves 5G wide stopband and high stopband isolation requirements.The size is 1.6×0.8×0.6mm,which has been used in 5G enterprise network signals.(2)Half-lumped half-segment balun filter design.In order to realize the equal amplitude inversion and frequency selection functions of the signal at the same time,the distributed band-pass filter is integrated with the lumped parameter balun up and down in cascade,which greatly reduces the volume.The filter uses a three-layer folded stripline structure to reduce the length of the transmission line.Z-shaped cross-coupling is introduced to increase the stopband suppression.Balun creatively proposed a termination capacitor structure to optimize the amplitude and phase difference,which is beneficial to reduce the spiral inductor layer.It can reduce the size and suppress the DC echo signal at the same time to achieve high suppression requirements.The size of the balun filter is 2.5×2.0×1.2mm,which has been applied in 5G base stations.(3)5G duplexer design.Using the LTCC's unique embedded feature in the device to integrate low-pass and band-pass,a broadband 5G duplexer and a dual-bandpass 5G duplexer were designed.In order to reduce parasitic coupling between components and reduce insertion loss,the band-pass branch adopts a high-low-pass cascade structure,and the parallel and series resonances are added to the two branches to form a zero point to improve the stop band suppression.The effect of crosstalk between small pass bands.The two duplexers have strict specifications,complex structure and flexible layout.In order to improve the yield and reduce the design cycle and cost,a "multi-port" simulation optimization and performance reverse adjustment method is proposed to greatly improve the simulation pertinence and reduce the design difficulty.Also,it has certain reference significance in engineering design.The 5G broadband duplexer will be used in handheld terminal devices with a size of 2.5×2.0×0.8mm.The miniaturized dual bandpass duplexer is applied to the MT7668 chip module with a size of only 1.6×0.8×0.7mm.