基于UWB 系统的巴伦滤波器组合器件

UWB 超宽带系统的快速发展对滤波器和巴伦的带宽、损耗提出了新的要求。平衡滤波器能够实现良好的匹配和滤波特性，插入损耗较小，但仅适用于窄带情况；表贴巴伦和滤波器同时使用时不仅占用较大面积，彼此间的干扰会降低系统性能。本文采用补偿法，将多层LC 滤波器和宽带Marchand 巴伦通过耦合电容连接制作在同一LTCC 基板内，减小面积的同时，缺点互补，巴伦改善了滤波器的衰减特性，滤波器改善了巴伦的匹配特性，适用于UWB 宽带应用。根据这一思路制作的巴伦-滤波器的中心频率为7.65GHz，带宽为1GHz，幅度失配≤0.2dB，相位失配≤4.5°，5GHz 处带外衰减≥60dB，9GHz 处带外衰减≥40dB，元件尺寸为7mm*3mm*0.6mm

Combination of Blun and Filter Based on UWB System

Balanced filter can achieve good performance in match, filter characteristic, and insertion loss, but only in narrow band application. Surface mounted filter and balun used at the same time not only take up larger area, but also may reduce system performance because of interfere between them. The LC filter and broadband Marchand balun are realized in the same LTCC substrate by coupling capacitor. This way can not only reduce size of devices, the two components can also compensate each other. Balun improves the attenuation characteristics of the filter; filter improves the matching characteristics of the Balun for broadband applications. The proposed balun-filter has center frequency of 7.65GHz, bandwidth of 1GHz, amplitude mismatch less than 0.2dB, phase mismatch less than 4.5°, attenuation more than 60dB at 5GHz, and attenuation more than 40dB at 9GHz. The size of this proposed balun-filter is 7mm*3mm*0.6mm.