Fabrication of monoblock ceramic bandpass filters with attenuation poles

Small size and rapid attenuation rate are two important factors in the selection of bandpass filters for practical applications. This paper describes a monoblock and modified Chebyshev-type bandpass filter with an attenuation pole in the lower stopband. The equivalent circuit consists of resonators, and series capacitance is presented to predict the filter performance. The series capacitance is made directly by an appropriate choice of the electrode pattern. Since no additional lumped element is needed, the designed filter shows a simple structure. Also, a compact monoblock bandpass filter using high-permittivity ceramics of (Ba, Sr)O-Sm₂O₃-4.7TiO₂ is fabricated. Experimental results of the fabricated filter measured by an HP8510B network analyzer verify the expected effect.