Multilayer Miniaturization Of Filter Design And Implementation

The filter, as a key component of microwave/RF circuits and systems, has thecharacteristic of frequency selective transmission. And rapid developments of wirelesscommunications applications challenge the filter with requirements "high-performance,miniaturization, low-cost, light-weight, highly reliability", which become the researchhotspot of microwave filter.This thesis, based on LTCC multilayer technology, researches the theory andstructure of high-performance and miniaturized microwave filter. Work of this paper isas follows:First of all, for high stopband-rejection requirements of the filter, the filterdesigned in this paper is based on cross coupled structure. Contrast to the traditionalstructure, cross coupled structure can realize highly select response with fewer orders.Cross coupled filter model and three kinds of symmetric coupling structure are analyzed.Process of extraction of the two design parameters is described, including couplingcoefficients and external quality factor. In addition, cross coupled filter can achieve asymmetric or asymmetric stopband suppression, which highlights its highly selectiveadvantages and design flexibility.Secondly, filter miniaturization technology is analyzed, including LTCC multilayertechnology, stepped impedance resonator (SIR), and capacitive loaded techniques. Inthe third chapter, for realization of the miniaturization filter, VIC is used to realizecapacitive loaded techniques. Filter A and B with the center frequency of1.2GHz areanalyzed, whose bandwidth are60MHz and200MHz. Transmission zeros are1.63GHzand1.73GHz, which appear in the upper stopband. SIR and capacitive loadedtechniques are used to realize filter C working in the WLAN band, and D working in theWiMax band. Combined with the LTCC process, changes in the permittivity of themedium and line width, may affect the filter transmission performance, so capacityanalysis is needed. Simulation software HFSS is used to simulate and analyze theimpact of the filter PCB test ground plane. Finally, based on high-density integrated engineering center of Sichuan Province,proposed filters are fabricated and tested. The size of SIR structure filter C is2.37mm×5.68mm×1.23mm, which verifies the feasibility of miniaturization filterdesign with cross coupled LTCC multilayer structure.