Research On Miniature Balun Filter Based On LTCC Technology

With the rapid development of wireless communication technology,higher requests have been put forward for the communication industry,such as miniaturization,high performance,for electronic equipment,RF system and the microwave components required.The low temperature co-firing ceramic(LTCC)technology using 3D integration technology,can realize the miniaturization of microwave components,low cost and high performance.At present,the balun filter based on LTCC technology is widely used in mobile communication,bluetooth,wireless local area network and other fields.But the emphasis of the research to balun filter design field is how to make balun filter which is better at miniaturization,good phase balance and amplitude balance.This paper revolves around miniaturization of balun filter based on LTCC technology for the study,and obtains the following results:(1)Theoretical analysis was carried out of the two baluns,respectively,and on the basis of theory in HFSS software for 3D modeling and simulation,designed the lumped parameter narrow-band balun and three lines modified Marchand broadband balun,which realized the miniaturization,good phase balance,amplitude balance and other performance.The sizes are both 3.2mm×4.5mm×0.95mm.(2)Theoretical analysis and design was carried out of three band-pass filters based on LTCC technology.The three types included the semi-lumped parameter filter,four-order distributed parameter filter and six-order distributed parameter filter.The adoption of cross coupling structure to these filters could add transmission zeros,which could realize the high restraint out of band.And it realized the miniaturization of filter transmission by electromagnetic coupling between the parallel resonant element.The sizes are less than 3.2mmx3.2mmx 1.4mm.(3)Cascaded the balun and filter designed by means of interconnecting each other through vertical hole,respectively.And then we could get three combined balun filters.This combined balun filter has the flexible combination characteristics of frequency,bandwidth and structure,and it has more widely application,good phase balance.The size of combined balun filter is smaller than the sum of the sizes of balun and filter.The sizes are less than 3.2mmx4.5mmx 1.98mm.(4)Using short circuit coupling stripline as resonant unit and based on the theory of short circuit coupling stripline,designed four balun filters of single element type.This kind of balun filter could realize the function of balun and filter at the same time,and has simple structure,smaller size.It also has the advantages of miniaturization,good phase balance.The sizes are less than 2.5mm×2.8mm×1.1mm.