Design method and fabrication techniques of polithic crystal filters with attenuation poles are described in detail. First, the concept of energy trapping is reviewed briefly according to the analysis by Minalin and equivalent circuits of coupled resonators are discussed and an accurate calculation method for tuning frequencies is proposed. Coupled resonators with a bridging capacitor are analyzed and adopted as the technique achieving attenuation poles.
And also, an equation for determining accurate attenuation pole positions is derived. Design procedure of polylithic crystal filters with attenuation poles and fabrication procedure and techniques of coupled resonators are discussed, and it turns out that developed theories are well-fit to the experimental results. Finally, problems remaining to be solved are discussed and a particular consideration is given to the fabrication techniques required for mass production. Experimental results show the possibility of the mass production in this country.
