The Design Of Passive Filter And Coupling Filter

Filter is a kind of circuit that can select the needed signal from the wideband range and restrain the frequency that is not needed. We can use it to divide or combine different frequencies, such as frequencies in amplifier ,mixer and multiplexing circuit in communication.This paper discussed the design theory of analog filters circuits systemically,from proposing the performance target to an actual filters circuit. The method being different from original analog filters design has been introduced. Through MATLAB ,we can get the analog filters coefficients and then transfer it to the second order section other than via complex operation.Then we studied the basic Principle of filters,introduced the structure and transmission equation of micro-strip , and realized lumped with microstrip device . Discussed the composition of the basic unit of microwave coupling Filter----Circuit design, the equivalent circuit and formulas of Half wave series resonators .We analyzed an end-couple BPF,a half-wavelength resonator BPF,a hair-Pin line BPF,and an interdigital BPF using the traditional thin film technology. Introduced the relevant factors affecting the performance.