具有傳輸零點之耦合濾波器電路

In the modern wireless communication systems, filters are used in the RF front end due to reject the unwanted spurious and image signals. In order to reduce the weight and volume of system, small size ceramic filters realized in synchronously tuned coupled-resonator configuration are commonly adopted. In this invention, we devote a different feature of realizing transmission zero which proposed in the synchronously tuned filter. These transmission zeros are located at the specified higher and lower stop bands without degrading the high frequency rejection. A filter design procedure modified from the conventional design method is proposed. According to the request extra attenuations at the specified frequencies and desired passband bandwidth, the values of filter elements can be determined. Then appropriate layout for realizing the practical filter on conventional PCB substrate is analyzed by using commercial EM simulator. A filter prototype operated at 5.2GHz is designed and fabricated to verify the design concept. The filter configuration is compact and easily implemented by conventional PCB technology without via-hole connection. The measured characteristics of filter prototype meet the most specification of HIPER LAN communication systems.