一种小型化超宽带微带带通滤波器

A compact ultra-wideband microstrip bandpass filter

研究一种小型化超宽带微带带通滤波器。该滤波器采用2个开路枝节线和2个短路枝节线,其中开路枝节和短路枝节两两组成枝节线对。在2个枝节线对之间,利用一段均匀微带线进行连接。滤波器的输入输出采用直接馈电的设计,以保证宽带滤波器所需的强耦合。通过对该滤波器的参数进行仿真研究,设计实现了一个带宽在110%左右的超宽带滤波器。试制样品的测试结果与仿真结果吻合良好,表明该滤波器在中心频率为1.90GHz时,可实现103%的相对带宽。通带内的最小插入损耗为0.20dB(在1.52GHz处),匹配均优于-20dB。第一个寄生通带的频率高于6GHz,是中心频率的3.2倍左右,而且该滤波器的电尺寸小,在其通带中心频率处,只有0.21×0.18λ2g。

We developed a compact ultra-wideband microstrip bandpass filter, which is composed of two pairs of stubs; in each pair, one stub is short-ended and the other open-ended. The two stub-pairs are connected via a section of uniform microstrip line. A direct coupling topology is applied to realize the feeding, so as to guarantee the tight coupling for wideband filter. Parametric studies are employed to demonstrate the performance of the filter, and then an ultra-wideband filter with about 110~ fractional bandwidth is designed and implemented. The measured result agrees well with the fullwave predictions, showing that the filter has a fractional bandwidth of 106% at the central frequency of 1.90 GHz. The minimal insertion loss is 0. 26 dB at 1.5 GHz, when the matching is better than --20 dB within the passband. The first spurious frequency is higher than 6. 0 GHz, about 3.2 times as much as the central frequency. Furthermore, the developed filter has a compact electrical size, about 0.21×0.18λg^2 at its central operating frequency.