Abstract: In order to provide a sufficient isolation between the resonators of a band-stop filter, prior art band-stop filters must be manufactured from separate ceramic resonator blocks. According to the invention the band-stop filter can be manufactured in a single ceramic block (1), having on one side surface strip-like areas (14; 15) of electrically conducting material extending perpendicularly from the bottom edge to the top edge and being located in the area between the resonators (A and B, B and C) and having dimensions selected so that they substantially cancel the electric and magnetic field between the resonators. If necessary, the coupling between the resonators can be adjusted by changing the width of the strip-like areas (14; 15) or by providing them with discontinuities.

Abstract: A temperature compensated filter comprises a block (1) of dielectric material having at least one transmission line resonator (3) formed herein. All surfaces except one side surface of the block are substantially coated with an electrically conductive layer (11). For achieving temperature compensation, a capacitor (6) coupled to the conductive layer (11) through a strip line (7) is attached, in a heat conductive way, to the uncoated side surface of the dielectric block. The capacitor (6) tunes the main resonator and the temperature dependence of its frequency is opposite that of the dielectric body so that it compensates the temperature dependence of the frequency of the main resonator.

Abstract: An inexpensive and lightweight air insulated high frequency filter can be made utilizing a radio device's frame and a printed board (15) intended for electrical circuits, so that during manufacture of the printed board (15) it is machined so that several side by side finger-like projecting tongues (14.sub.1, 14.sub.2, 14.sub.3, 14.sub.4) are formed, which are entirely coated with electrically conducting material. Thereafter the printed board, on which electrical and mechanical components intended for it are mounted, is placed in the radio device's crate-like frame made of conducting material and possibly provided with partition walls (18, 19), and on which also cover parts are fastened so that the tongues will be parallel with them and located between them, whereby the tongues, the enclosing cover parts and the frame wall parts form a filter structure.

Abstract: Previously it was not possible to realize a ceramic duplex filter using a single monolithic ceramic block, because the isolation between the transmitter branch and the receiver branch could not be made sufficiently high. A duplex filter (1) can be realized in a single ceramic block by making, between its filters (A and B), a strip-like area (9) on the non-coated surface (5) of the ceramic block, due to which the electric and magnetic coupling between the resonators (R.sub.4, T.sub.1) of filters (A and B) on each side of the area can be adjusted to almost zero. This "electric partition" (9) provides a sufficient isolation between the filters of each branch.

Abstract: A dielectric filter is formed from a block of ceramic material with holes extending from a top surface toward a bottom surface. At least the bottom, both ends and one side surface are coated with conductive material. Also, the interior surfaces of the holes are coated with conductive material to form transmission line resonators. The uncoated side surface has an electrode pattern which allows coupling to the filter and between resonators of the filter. The elevation of the electrodes on the side surface between the top and bottom determines whether the coupling is capacitive, mixed inductive and capacitive, or inductive.