中文摘要：

提出了一种新型微带三频滤波器，滤波器由两个弯折并相互嵌套的分支线谐振器和一个T形谐振器组成。谐振器之间相互耦合，得到三通带频率响应特性。该滤波器可通过调节微带线几何参数改变通带位置以及带宽，以满足不同应用需求。这种结构的滤波器结构紧凑，电路面积小，三个通带两边各引入一个传输零点，增强了通带间的隔离度以及阻带抑制特性。设计并制作了一款1．57／3．55／5．2GHz三通带滤波器，测试结果与仿真结果基本相符，验证了该滤波器结构的有效性。

英文摘要：

In this paper, a novel structure for designing tri-band passband filter based on mi- crostrip is proposed, which is composed of a pair curved branch line resonators and T-shaped res- onator. The resonators are coupled to each other to obtain the frequency response of tri-band passband characters. The center frequencies and bandwidth of the passbands can be tuned to de- sired value by shifting the geometric parameters of the structures. This filter has the characters of small area and high selectivity and isolation for two transmission zeros located beside the three passband respectively. A tri-band passband filter at 1.57/3.5/5.2 GHz is designed and fabricat- ed. The simulated and measured results are found to be in acceptable agreement with each other, which verifies the validity of the proposed filter structure.