The Miniaturization Of Cavity Filter

With the rapid development of science and technology, the target of system that use electromagnetic waves to achieve a certain function becomes higher. Microwave filters as an indispensable component,which gives new challenges for the design of microwave filters.The design of filter appearing the trend of small size, lightweight,low loss,high rejection, high power-handling capacity, spurious band far away from the passband.Along with the development of new materials and new technology,more and more new filters that have good performance than cavity filters in some areas are presented.For instance, microstrip Filter shows the advantages in three areas, flexible design, lightweight, cheaper process,adapts to volume manufacturers and equipment integration.The HTS filters have good performance of very low loss,and so on.It is irreplaceable that cavity filters with high power capacity,perfect technology,low loss and so on.So far,the application of the cavity is widespread popularity. Therefore,it has pratical significance to study miniaturized technology of cavity filters.The resonator and coupling structure are the two important parts of the filter.The filter made up of resonance cavitys that connected by the coupling structure.This paper labor the filed distribution, resonance frequency and Q value of the resonator cavity.And present the miniaturized technology of the coaxial cavity and waveguide cavity.And detailed analysis two new coupling structure,the one is called resonant coupling structure and the other is Electric and magnetic mixed coupling structure. Real microwave structures about the two new coupling structure have been proposed,and a few microwave filters are designed with those new coupling structure to research its properties.Results demonstrate the resonant coupling structure can realize different coupling nature (capacity or inductive) at different frequency bands and electric and magnetic mixed coupling has the characteristics of creating transmission zeros.Finally,a filter that from actual engineering design is designed with the knowledge that presented this paper.Measured results are completely meet the design requirements and presented to demonstratethe validity of this novel approach.