具有耦合度增强和宽带杂散抑制的新型双模滤波器(英文)

NOVEL MICROSTRIP DUAL-MODE BANDPASS FILTER WITH COUPLING ENHANCEMENT AND WIDEBAND SPURIOUS RESPONSE SUPPRESSION

针对传统耦合结构的双模微带滤波器端口耦合度受限于加工精度及存在二次寄生通带等问题,提出了一种新型双模滤波器。该滤波器采用弯折偏移馈电型的耦合结构,结合阶跃阻抗双模谐振器,能够在提高端口耦合度的同时有效抑制谐波响应。在此基础上,针对级联双模滤波器的近边带杂散问题,通过分析杂散响应频点变化规律和模式电流分布,并利用该新型滤波器自身传输零点可控的特性,优化寄生谐振器的结构参数,有效抑制了近边带杂散响应。仿真和实验表明,与传统双模滤波器相比,该设计具有插入损耗低、过渡带陡峭、阻带宽的特性,在宽带通信中的杂散抑制方面具有较好的应用价值。

The microstrip dual-mode filter （DMF） with conventional coupling structure has some limitations in- eluding the port coupling strength limited by fabrication tolerance and the existence of serious second order spuri- ous band. Therefore, a novel DMF with a offset-feed bended coupling structure and a stepped-impedance dual- mode resonator is proposed for coupling enhancement and spurious response suppression. Based on the analysis of the change of spur frequencies and the current distribution of spur resonant modes, all spurs near passband of the cascaded DMF can be fully suppressed by optimizing the structure parameters of parasite resonators, which bene- fits from the inherent well-controlled transmission zeros. Experimental results show that the proposed DMF ex- hibits lower insertion loss ,much sharper rate of cutoff and wider spur-free stop band compared with conventional DMF. This design is applicable for spur suppression in wideband communication.