Design Of The Miniaturiztion Dielectric Duplxer

4G communication technologies widely used today, the demand for data traffic is still growing at a high speed. The small base stations in mobile communication base stations have played an important role in large data traffic service, and it’s advantages of small volume, small emission power and high frequency spectrum utilization are more and more prominent compared to the base station. The small base station requires a smaller volume of the microwave duplexer, therefore a smaller, better performance of the microwave duplex is urgently needed.This paper designed a miniaturized waveguide-cavity dielectric duplexer that can be used for small base stations in 4G communications. Its main feature which realizes the miniaturization is that the volume of the duplexer is only about one in three of an ordinary coaxial cavity duplexer. The structure is: the dielectric constant 40 of the ceramic dielectric block which size is litter smaller than the metal waveguide cavity is used to fill the metal waveguide cavity, dielectric block having through hole that be used for frequency tuning, then, making a small teflon ring put on the dielectric ceramic block to fix it. Each channel of the duplex is composed of seven resonant cavities, and the coupling between the resonant cavities is realized by means of the window. The 3,4,5 cavity of each channel consisting of a CT structure, results transmission zeroes in high-end of the low-pass band and low-end of the high-pass band. In the high pass band, the 3,5 resonator cavities using the dominant mode of the CT structure and the 4 cavity using a first high-order mode, will have a negative coupling coefficient. The coupling between input port and the first resonant cavities of each channel of the duplex use microstrip branch line to realize.A new tuning method which we called equivalent capacitance tuning method based on Q3 D Extractor is proposed in this paper. There is a problem that corresponding relationship between the equivalent capacitance and the insertion depth of the tuning screw cannot be established accurately in the original equivalent capacitance tuning method. The above mentioned problems are solved by the new method which directly establish corresponding relationship between the insertion depth of the tuning screw and the capacitance of the split cavity by Extractor Q3 D software. In practice we will establish a correspondence between the amount of change in the cavity capacitance and the amount of change of screw insertion depth. Compared with the commonly used method the tuning of Y matrix, new tuning has the advantages of reducing a lot of tuning time and demanding of memory and CPU, and tuning process is direct, simple, easy to understand and so on.The new method is illustrated by an example. The result of the initial curve is better than the tuning of Y matrix, but the time is only 1/3 of the Y matrix. so, It proved its advantages.Finally, the fabrication, testing and result analysis of the dielectric duplex are carried out.