输入输出电容对孔耦合同轴滤波器性能的影响

Effect of I/O Capacitor on Properties of Coaxial Filter Coupled with a Hole

为了提高滤波器的电性能,研究了孔耦合两腔介质同轴滤波器的调试技术。理论上分析了耦合谐振器的频率和有载品质因数(Q)值与输入、输出电容的关系。采用介电常数εr=74的微波介质陶瓷制作了孔耦合两腔介质滤波器,通过观察反射系数(S11)波形讨论了输入、输出电容对滤波器性能的影响。结果表明,反射系数的波形和大小能直接反映出输入、输出电容的大小是否合适。最后制作出中心频率为902MHz、通带带宽13.2MHz、阻带衰减(f0±40MHz)>24.9dB的带通滤波器。该调试技术对两腔以上介质滤波器的调试具有指导作用。

In order to improve properties of filter,the method of adjusting two-pole dielectric coaxial filter coupled with a hole had been developed.The relationships between frequency and loaded Q value of coupled dielectric resonator and I/O coupling capacitors were theoretically analyzed.Two-pole dielectric filter coupled with a hole was made of microwave dielectric ceramics with εr=74.The method of adjusting filter was discussed specifically by observing the S11 wave pattern.The results showed that S11 wave pattern and amplitude could reflect if I/O coupling capacitors were appropriate or not.Finally,the filter with the following characteristics was made： center frequency 902 MHz,pass-band width 13.2 MHz,stop-band attenuation at f0±40 MHz higher than 24.9 dB.The adjusting technique was proved useful for more than two-pole dielectric filters.