Research Of Ka-band Waveguide Duplexer

The rapid development of modern microwave communication technology makes the limited communication spectrum more and more congestion and lead the high requirement for filter’s performance.At the same tine,with the extensive apply of microwave integrated circuits,low cost, ease integration also become the basic requirements for the filter design. This thesis studied the design of the Ka band waveguide filters and diplexers which can meet the above requirements.E-plane metal insert filter is a classic type of filter structure.This structure with low insertion loss, simple structure, low cost and very suitable for the requirements of modern communication.The design of filter was based on the group delay theory and high frequency simulation software.By achieve the coupling coefficient between the cavity and the group delay of port in simulation software,a filter can be designed quickly and accurately.Though thinner thickness of the metal insert can get better performance, it’s also lead to processing difficulties.After analyzed the effect of the thickness and position of metal insert to the filter performance,a new filter structure is proposed. By offset the position of metal insert,the filter can get good performance with thicker metal insert.Though rectangular waveguide has a very good transmission performance, But the large size limits its application in microwave integrated circuits.Substrate integrated waveguide(SIW) is a new microwave transmission structure which developed in recent years.With the Advantage as high quality factor, low loss, small size and easy integration,it’s widely used in microwave and millimeter wave circuits.Because of the similar transmission characteristics with traditional rectangular waveguide,the substrate integrated waveguide can achieve most microwave devices which were achieved by rectangular waveguide.In this thesis filters based on substrate integrated waveguide were studied.Firstly,introduced the structure and transmission performance of substrate integrated waveguide.Based on the filter synthesis theory three types of filters were designed.The Simulation results shows that this filters can get high power capacity and good transmission performance with small size. The structure of diplexer is H-plane T junction connect two E-plane metal insert filter.According to the simulation results,a diplexer was machined and tested. The test results show that the diplexer insertion loss was too high and the center frequency had a offset.After the error analysis, these errors may generated by the process of machined and assembled.