Based On The Three-dimensional Structure Of Cross Coupling Filter Design And Implementation

At first, this dissertation researched the general theory of couplings for filters. Thisdissertation contained transmission function of cross-coupling filter, construction ofpolynomial, synthesis in cross-coupling coefficients matrix, rotation eliminationtechnology for the matrix and programmed software to synthesize the couplingcoefficients of cross-coupling filter by make full used of these processes. Finally,designed two microstrip bandpass cross-couplings filters which had a center frequencyof2.45GHz.The three dimensional structures technology promoted the microstrip circuits fromconventional two dimensional structures to three dimensional structures. Accordingly,three dimensional structures was propitious to minimization of microwave componentsand greatly improved the integration of the microwave system.Combining advantagesand three dimensional electromagnetic structures of the technology, researched aminimizing three dimensional multilayer microwave resonator. This paper also analyzedperformances of three dimensional electromagnetic microwave resonator, includedquality value of the resonator, secondary resonate frequency and how different distancesof the poles effected the resonate frequency.Resonate frequency of structures which had intercoupled resonators and howinner-coupling capacitor affected resonate frequency are derived from this dissertation.Afterwards, substituted lumped coupled capacitor with coupled microstrip, andanalyzed resonators with microstrip line coupled inside. Especially analyzed howcoupling coefficients effected on resonating frequencies, filter volume, and parasiticalpassbands.On the basis of these theories, proposed a three dimensional cross-coupling filterstructure. This dissertation pays attention on how the parameters on three dimensionalstructures affects filter performances. In addition, analyzed simulation results on mutualeffects on different three dimensional resonators, on different filter topologies includeon thickness affected electric coupling, magnetic coupling, mixed coupling and externalquality factor. Also researched characteristics of intercoupled-resonator filter in this three dimensional structures and designed a three dimensional4order cross-coupledfilter according to general theory of coupling. Designed cross-coupled filter introduced4-elements cross-coupling structure, a pair of transmission zeros to improve squarenessratio and moved the parasitical passbands to higher frequencies. Compared to a4ordermicrostrip cross-coupling filter which had the same characteristics, cross-coupling filterwith three dimensional structures technology had advantages in smaller size, moreexcellent rejection band and higher parasitical passbands.