Research And Design Of Multi-stage Microwave Filters Based On LTCC Technology

As the rapid development of communication technology,especially in wireless communication and network communication systems,the frequency resources have faced a great challenge.At the meantime,as the popularization of the mobile communication,the claims like miniaturization,high performance and high reliable have been made for radio frequency and integrated circuits.The microwave filter,as an important device during the communication system,determines the quality of the whole system.Therefore,the study on its miniaturization and high performance has been a hot issue which receives much more concern.By increasing the number of the resonator,the multistage filter effectively strengthen the coupling effect between the resonators.Therefore it improves the performance of the filter through increasing the out-of-band attenuation,reducing the shape factor of transition band to improve sideband steep and the performance of the filter.In addition,combining LTCC(:Low Temperature Co-fired Ceramic)technology,which possesses the merits of low cost,miniaturization,high temperature resistant,would attain the goal of miniaturization.This thesis focuses on the topic of 'the research and design of the multistage microwave filter based on LTCC technology',combined the basic theory of filter to explore the miniaturization design of the filter.According to different frequencies,structures and performance,the specific work is listed as follow:(1)Based on the low-pass prototype circuit theory,a low pass filter of six-order is designed with the cut frequency of 3.2 GHz.Symmetric cascade structure is used to optimize for good filtering quality and the size of the filter also meets the requirement.It not only improves the performance of the filter but also simplifies the modeling and debugging procedure during the complexity of the fitting.(2)Two multistage band-pass filters have been designed based on the structure of stripline.One is the eight-order with the center frequency of 3.45 GHz,the other one is the twelve-order with center frequency of 2.8 GHz.Firstly the single resonator is adjusted to determine the resonant frequency.Then the order is increased based on the coupling effect between the resonators.At the same time,Z type stripline is introduced for transmission zeros.The improvement and the influence of the filter through increasing the order have been done during the design procedure.(3)The band-pass filter with ultra-wide band performance have been designed.The center frequency is 7GHz and the relative bandwidth is 85.7%.Multimode resonator has been used in this model to provide wide bandwidth range whereas adding a defected ground structure improves the spurious passband performance in the high frequency zone outside the passband.In addition,the corresponding influential parameters has been discussed and summarized for the future study.These four filters designed in this thesis take the full advantages of the LTCC technology,also consider the requirements of the performance and size.Finally all of them obtained the excellent filtering performance and high integration.Two of them have been tested and the results match well with the simulation one.Also the yield reaches above 80%for wide application.