Matsushita Electric Industrial Co., Ltd.

Michiaki Matsuo

Mitsuo Makimoto

Morikazu Sagawa

Hiroyuki Yabuki

A filter of microwave and millimetric bands with spurious characteristic controlled is disclosed. A filter circuit on a top surface of the substrate including resonators electromagnetically resonating and coupled at a resonance frequency at a microwave band and a millimeter wave band, for filtering an input signal from the connectors through the resonator and outputting the filtered signal through the connector. The filter circuit is contained in a metal box including a top plate confronting the top surface and the filter circuit, side walls, and a bottom plate. An inside surface of the top plate has a shape other than a flat plane to control the spurious characteristic, that is, a protrusion. The bottom plate of the metal box may be coalesced. The spurious characteristic may be controlled by a hollow portion in the top plate. The protruding portion may be provided to the side walls. The spurious frequency may be controlled by a dielectric plate in the space in the shielding. Microstrip line resonators, patch resonators, or dielectric resonators are used as the resonator.

Filter with spurious characteristic controlled

A dielectric filter includes a dielectric block having multiple through holes which are created in parallel and grooves which are created around the opening of the through holes. A conductor is formed inside the grooves and the through holes. The inside conductors and in-groove conductors are connected at the opening of the through hole surrounded with the groove. The inside conductors and an outside conductor are connected at a second end. The opening of the through hole is formed inside an open-circuit end of the dielectric block.

Dielectric filter and RF apparatus employing thereof

A strip-line filter is provided with upper- and lower-stage resonators having the same electromagnetic characteristics. Each of the resonators has a one-wavelength square-shaped strip line and four open-end transmission lines connected to four coupling points A,C,B and D (or E,G,F and H) of each resonator which are spaced 90 degrees in electric length in that order. The square-shaped strip lines have a pair of parallel coupling lines closely placed in parallel to each other to electromagnetically couple the resonators. Therefore, the filter can be manufactured in a small size. A first microwave resonated in each resonator is electromagnetically influenced by two open-end transmission lines connected to two coupling points A and B (or E and F), and a second microwave resonated in each resonator is electromagnetically influenced by two open-end transmission lines connected to two coupling points C and D (or G and H). Therefore, resonance wavelengths of the microwaves can be longer than a line length of each square-shaped strip line. Also, the resonance wavelengths can be adjusted by trimming the transmission lines. Also, because all constitutional elements are made of strip lines, the filter can be made plane.

Plane type strip-line filter in which strip line is shortened and mode resonator in which two types microwaves are independently resonated

Plane type strip line filter in which strip line is shortened and dual

Plane type strip-line filter in which strip line is shortened and dual

A dielectric resonator is provided which includes a dielectric block, an inner conductor formed on an outer surface of the dielectric block, and another outer conductor formed on an outer surface of the dielectric block. The inner conductor is so geometrically modified as to change the characteristic impedance in a manner wherein the shape of either the inner conductor or the dielectric block is changed.

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Kawasaki, Japan

Michiaki Matsuo