Surface-mount cavity filter technology

A method is proposed to realize cavity resonator filters for cellular frequencies in surface-mount technology. The cavity resonators can be produced by molding techniques and subsequently soldered onto a circuit board, where a stripline structure in the circuit board makes the coupling between the resonators. The molded parts for all resonators of a given filter can be identical. Means are proposed for dealing with the alignment accuracy of the mounting process. Temperature effects due to thermal expansion can be accounted for. Three- and five-resonator band-pass filters have been designed using combined field and circuit simulation techniques, built, and measured.