5.83 GHz宽阻带高抑制小型腔体滤波器设计

Design of 5.83 GHz small cavity filter with wide stopband and high suppression

针对U-NII频带宽带无线接入系统射频发射信号谐波过高的问题,设计了一款小型四阶宽阻带高抑制腔体滤波器用于对发射信号的谐波进行抑制。该腔体滤波器采用矩形单腔结构,单腔内的四个矩形柱在激励下分别产生四个不同谐振频率的TEM电磁波,相邻矩形柱的TEM波相互耦合实现信号传输,同时给出了腔体中矩形柱高度、相邻矩形柱间距、端口高度对谐振频率、耦合系数和外部Q值的影响。实测性能参数为:中心频率为5.83GHz,通带带宽为60 MHz,带内插入损耗≤0.65,回波损耗≥17 dB,中心频率的2次倍频11.66 GHz频点抑制≥100dB,带外抑制大于60 d B频率范围为6.45~14.6 GHz,滤波器尺寸仅为67 mm×12 mm×18 mm。测试结果表明该结构的腔体滤波器具有结构简单、尺寸小、阻带宽和谐波抑制高的特点。

Aiming at the problem of high harmonics of RF signals transmitted in U-NII broadband wireless access system,a small fourth-order cavity filter with wide stopband and high suppression was designed to suppress the harmonics of transmitted signals.The cavity filter was designed with rectangular single cavity structure.Four different resonant frequencies of TEM electromagnetic wave were produced under the excitation in single cavity with four rectangular columns respectively.The TEM waves of adjacent rectangular columns were coupled to realize signal transmission.The relationships between resonant frequency,coupling coefficient,external Q-value in the cavity and rectangular column height,and the spacing of adjacent resonant columns andport height were given.The measured result indicates that the designed filter features a center frequency of 5.83 GHz,passband bandwidth of 60 MHz,in-band insertion loss of less than 0.65,return loss of greater than 17 dB,suppressionat 11.66 GHz(double center frequency),of greater than 100 dB,out-ofband suppression of greater than 60 dB in the frequency range of 6.45-14.6 GHz,and size of only 67 mm×12 mm×18 mm.The results show that the cavity filter has the advantages of simple structure,small size,wide stopbandand high harmonic suppression.