Dielectric filter having resonators aligned to effect zeros of the frequency response

摘要

A dielectric filter advantageously comprises a body of a dielectric material rectangular in cross-section and confining at least two parallel holes (31', 32', 33') that extend through the body parallel to each other and parallel to the side surface (34) plane. Major portions of the body are coated with a conductive material which also covers the inner surfaces of the holes (31', 32', 33'), hence forming a transmission line resonator for each hole. The resonators may be quarter-wave or half- wave resonators. According to the invention, the holes are located on at least two lines in the long direction of the body in which case the center axis of at least one hole (32') is not located on the same plane parallel to the side surface (34) as the center axes of the rest of the holes. Advantageously, the distance (D) of the center axis of a hole from the center axis of an adjacent hole is identical for all holes. In this manner it is possible to manufacture a filter that has a smaller volume than a filter with identical electrical characteristics having all the holes on one line.