基于T型枝节加载SIR的双频微带滤波器的设计

Design of dual-frequency microstrip filter based on T-branch loading SIR

针对当前通信系统需要滤波器支持多频段、小型化和高性能等要求,提出了一种基于T型枝节加载SIR的频率独立可控双频微带滤波器结构.针对该谐振器,利用提出的特殊电耦合结构实现滤波器的小型化,并引入零度馈电结构构造传输零点来改善阻带抑制,最终得到覆盖WLAN2.4GHz和WLAN5.2GHz两个频段且占用尺寸仅为16.5mm×21.7mm的双频微带带通滤波器.由仿真结果显示,两个通带的中心频率分别为2.45GHz和5.2GHz,带内最小插入损耗分别为0.35dB和0.47dB,带内最小回波损耗分别为-44dB和-34.8dB,3dB相对带宽分别为28.9%和11.3%,阻带抑制也因引入三个传输零点而大大改善.该滤波器结构整体尺寸小、插损低、频带宽且带外抑制特性好,具有一定的实际应用价值.

To meet the requirements of multi - band, miniaturization and high performance in the current communication system, a frequency independent controllable dual-frequency microstrip filter structure was proposed based on T-branch loading SIR. For the resonator, special electric coupling structure was used to realize the miniaturization of the filter, and the zero-degree feed structure was introduced to construct the transmission zero to improve the stop band suppression. Finally, a dual-frequency microstrip bandpass filter was obtained covering WLAN 2. 4 GHz and WLAN 5. 2 GHz, which only occupies a footprint of 16. 5 mm ×21. 7 mm. The simulation results show that the central frequencies of the two passbands are 2. 45 GHz and 5. 2 GHz respectively. The minimum in-band insertion lossis 0.35dB and 0.47d Brespectively. The minimum in-band return loss is -44dB and -34.8dB respectively. The 3 dB relative bandwidth is 28. 9% and 11. 3% respectively, and stopband rejection is also greatly improved by the introduction of three transmission zeros. The filter structure has small overall size, low insertion loss, wide frequency band and good out-of-band rejection characteristics, and has certain practical application value.