Four-order cross-coupling band pass filter

Abstract

The invention discloses a four-order cross-coupling band pass filter which comprises input and output feeder lines, bandstop structures and first and second resonators, wherein the first and the second resonators are oppositely arranged; a double-mold third resonator is coupled in the first and the second resonators; the first and the second resonators are in the completely same open-loop structure and are used for realizing the coupling of interstage signals; the third resonator is a center loading resonator and comprises an open type microstrip line and a T-shaped structure, wherein the length of the open type microstrip line is the semi-wave length of the center frequency of the filter; the third resonator is embedded in the first and the second resonators to form cross coupling; the input and the output feeder lines are respectively connected to the first and the second resonators; and the two same bandstop structures are loaded on the input and the output feeder lines. According to the invention, the double-mold resonator is embedded between the two semi-wave resonators which are mutually coupled, and simultaneously, an asymmetrical feeding manner is adopted and the bandstop structure is increased, so that the filter has high-frequency selectivity and wide bandstop characteristics.

Description

technical field [0001] The invention relates to a microwave microstrip filter, in particular to a fourth-order cross-coupling band-pass filter with high frequency selectivity and wide stop band. Background technique [0002] Microstrip bandpass filters with small size, high frequency selectivity and wide stopband, as an important device in the front end of wireless communication systems, have attracted more and more attention from researchers. [0003] High frequency selectivity means that the transition between the passband and stopband of the filter's frequency response is very rapid, and introducing a transmission zero between the passband and stopband will greatly improve the frequency selectivity of the filter. Hong J-S et al proposed an open-loop fourth-order cross-coupled bandpass filter in 1996 (J. S. Hong, and M. J. Lancaster, "Couplings of microstrip square open loop resonators for cross-coupled planar microwave filters," IEEE Trans. Microw. Theory Tech., vol. 44,...

AI Technical Summary

Problems solved by technology

However, once the size of the stepped impedance resonator or the defect ground structure changes, it will often have a greater impact on the passband performance of the filter, which is not easy to design

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