基于平行耦合线的双陷波超宽带滤波器设计

Design of Ultra-Wideband Bandpass Filter with Dual Notch Bands Based on Parallel Coupled lines

基于半波长平行耦合线结构,设计了一款高选择性的双陷波超宽带滤波器。首先通过半波长平行耦合线级联低阻抗传输线实现了超宽带带通滤波器;然后在平行耦合线两端加载阶梯阻抗谐振器,在通带两侧各产生一个传输零点,增强了超宽带滤波器的选择特性;最后通过引入短路阶梯阻抗旁路耦合的方法实现了超宽带滤波器的双陷波特性。利用HFSS进行仿真后结果表明,该超宽带通带范围为3.15GHz-10.15GHz,通带内插入损耗在0.5dB左右,且通带内群时延均小于1ns,上、下截止边沿衰减斜率为86.9dB/GHz和71.8dB/GHz,双陷波中心频率分别在5.81GHz和8.0GHz,双陷波内插入损耗均大于10dB,具有良好的抑制水平。

An ultra-wideband(UWB) bandpass filter with dual notch bands and high selectivity characteristic is proposed based on parallel coupled lines. The ultra-wideband bandpass filter is realized by cascading the half wavelength parallel coupled-line with low impedance transmission line. Two step impedance resonators(SIR) are placed at the two ports of coupled lines, which leads to two transmission zeros in the lower and upper passbands, and the performance of the passband selectivity is improved. The method of by-pass coupling resonator is applied to introduce dual notch bands in the passband of this ultra-wideband(UWB) bandpass filter. The results of simulation by HFSS show that the bandwidth of the ultra-wideband bandpass filter is 7GHz(3.15-10.15 GHz), the insertion loss is about 0.5 dB, the group delay is less than 1 ns and the attenuation slopes of the upper and low passbands are 86.9 dB/GHz and 71.8dB/GHz. The center frequencies of this two notch bands are 5.81 GHz and 8.0GHz, and the insertion loss in the notch bands are all largeer than 10 dB, which shows a good out-of-band rejection.