The Study Of High-power Filters In Wireless Communication System

With the rapid development of the modern microwave communication techniques, the spectrum is becoming more and more precious and crowded. The requirements for microwave filters with high selectivity, low loss, low PIM and low cost are increasing, which promotes the deeper research for the microwave filters. Now days, with the improvement of computer capacities and technique of microwave CAD, the precision and efficiency of the high frequency simulation softer is rising highly. So we can associate the equivalent circuit method with the softer of high frequency simulation, to improve the characteristics and shorten the design period.The aims of this paper are to study the design method of high-power band pass filter in wireless systems. The main work of this paper includes: 1.The coupling method is used to design Chebyshev filter after coupling matrix is made by equivalent circuit network; it can improve the selectivity of out band by using CT or CQ cross coupling.Then it synthesizes the equivalent circuit by using simulation software and gets the filter response,coupling coefficient and outer Q value, in the end the physical size of filter can be designed according to coupling coefficient and outer Q value .2. The paper studies the cause of PIM and offers the methods which can improve PIM;3. First of all ,the paper computes the stored energy of resonator in equivalent circuit and factual field density of the resonator by using simulation software;it presents method of improving temperature compensation of filter and designs the temperature compensation characteristic by using simulation software.In the end, based on the theory and the conclusion, this paper designs and manufactures the high performance filter of wimax system base-station. The results prove the validity of this design method by exactly measuring filter parameters.