Dual-band Theory On Equal-length/Unequal-length Stepped-impedance Resonator And Its Applications On Filters

As everyone knows, SIR was always treated as two multipled LC series circuits in originaldual-band analysis method. This paper mainly put eyes on the analysis of the shortest electrical lengthof SIR with its response, which is calculated by using Z-transform technique.We found that there are many solutions of impedances values and electrical lengths to theresonance formula of SIR. So we have a deeper transformation on the resonance formula of SIR inchapter3, then we got a function f (x). In this chapter, we have these conclusions: While thedual-band ratio(ratio of second harmonic to first harmonic) is less than3, SIR has got a minimumvalue at the condition of equal-length. But as the dual-band ratio is more than3, a conclusion wasdrawn out that with the decrease of the function value, we could got less electrical length of SIR. Inthe condition of frequency ratio equals3,/4impedance resonator was taken into use.As more, in view of combining the engineering application, in the next chapter, we tookZ-transform method in to the analysis and calculation of the transmission matrix, and compared thereresponses. In the last part of this paper, a filter design method based on Z-transform technique wasgiven out, and design process of two types of filters (a low-pass filter and a dual-band band-pass filterwhich combined a wide-band band-pass filter with a band-stop filter) were given out as examples.The advantages of this method id that the structure of filters designed by using this method is simple,and is accurately.