Abstract: An advantageous embodiment of the invention is the filter of the receiver branch of the duplex filter in a multi-channel radio transmitter/receiver having reception and transmission bands composed of plural radio-frequency channels. In the first state of the filter, when the radio transmitter/receiver is only receiving radio signals, the width of the pass band of the filter corresponds to said reception band. In the second state, in which the radio transmitter/receiver additionally transmits radio signals, the pass band of the filter is switched by current control to cover only part of the reception band. By constructing the filter in the manner proposed it is possible to use current control in the first resonator in the filter of the receiver branch. Because of its power consumption current control is otherwise unsuitable for use in e.g. the duplex filter of a portable radio-telephone.

Abstract: The present invention relates to a coupling element (21) by which the coupling of a resonator (24) is adjusted in a radio frequency filter. The coupling element of the invention is a strip made of flexible conductor material being shaped symmetrical relative to the normal, that is, the symmetry axis of the longitudinal axis extending via the centrepoint of the strip in the longitudinal direction. The strip (21) is fixed at least at two points of an edge in the longitudinal direction to the circuit board (25) either by surface mounting on pads (33, 35, 36) or by soldering into holes borred in the circuit board to be at appropriate space from the resonator coil (34) and from the surface of the circuit board (25). One (33) of the fixing points is grounded and another (36) is connected to the signal conductor in the filter. The coupling can easily be adjusted by bending the board relative to the symmetry axis either one-sidedly or on both sides.

Abstract: A transmission line resonator is disclosed which has a resonance frequency that is electrically controllable by control voltage. A reactive circuit is coupled in parallel between two coupling points on the transmission line resonator. The reactive value of the reactive circuit is changed by the control voltage. The reactive circuit can be inductive or capacitive. The control voltage can switch the reactive circuit in parallel with a part of the transmission line resonator between the coupling points, or can control the capacitance value of a capacitance diode disposed in parallel with a part of the transmission line resonator between the coupling points.

Abstract: The present invention relates to a radio frequency filter the resonators (6,7) of which are made up of a wire wound into a cylindrical coil comprising a number of turns and of a surrounding casing (41). Finger-like projections (3) of an insulating plate (1) support the conical coils from the inside, and the coupling to the resonator is from a microstrip line (8), at a tap point (21), on the insulating plate. Each cylindrical coil has, adjoining the first turn, a straight portion (2) which is parallel to the axis of the cylindrical coil and extends towards the bottom plate (44) of the filter. On the inside surface of the bottom plate (44) there is a lead (51) one end (E) of which is short-circuited and the other end open, and the tip (12) of the straight portion (2) adjoining the cylindrical coil (6) is in contact with this lead (51).

Abstract: In the mechanical supporting of the resonator coil it is known to use around the resonator coil an injection moulded plastic U-shaped binder ring, with the loops of the coil running through the arms in the binder ring. The resonator wire can also be wound around a plastic body. The methods of the prior art considerably weaken the Q value of the resonator. According to the invention it is possible to achieve good supporting, without a weakening of the Q value, in such a way that the resonator coil (1) is supported from at least one point by a supporting leg (6) of metal, which one end is fastened to the wire of the resonator coil (1) and the other end is fastened to an insulation piece (8) having low losses, which in turn is fastened to the installation plate.

Abstract: The invention relates to a dielectric resonator comprising a block (2) of dielectric material, having upper (9), lower and side surfaces and in which there is a hole (3a) extending from the upper surface to the lower surface. The hole (3a) and the lower surface as well as at least part of the side surfaces are coated with an electrically conductive material and at least the upper surface (9) is uncoated so that the hole (3a) thus forms a transmission line resonator. The uncoated surfaces are covered with a lid (5) of an electrically conductive material, whereby the dielectric block is substantially surrounded by an electrically conductive material. The resonator hole (3a) is composed of two portions, a straight portion (3a) beginning from the lower surface of the dielectric block as well as a wider portion (10) that is formed above the straight portion and opens into the upper surface (9) of the dielectric block.

Abstract: A transmission line filter comprises four resonators (100, 200, 300, 400), and transmission zeroes can be added to the transfer function of the filter using a known phasing coupling technique using a transmission line (53, 54) coupled between two resonators. The location of the transmission zeroes can be varied using control circuits (A,B). Each control circuit comprises a series coupled inductance (55, 58) and capacitance (56, 59) forming a resonance circuit, the resonance frequency of which can be varied using a variable d.c. voltage (V.sub.1, V.sub.2). The inductance of each control circuit is arranged adjacent its respective transmission line so that the two are weakly electromagnetically coupled. By supplying the variable voltage to the resonance circuits, normal operation of the phasing coupling is affected, thereby varying the location of the transmission zero. One or more control circuits can be provided for filters having transmission zeroes in their transfer function which need to be varied.

Abstract: A dielectric filter (1) comprises a body of dielectric material, having two bores (3) running therethrough acting as resonators. The sides of the body are covered in a metallic coating apart from an upper surface (2) and one side surface (4). Electrode patterns are provided on the uncoated side surface to provide inductive and capacitive coupling between the resonators. By providing switches 8, the ratio of inductive to capacitive coupling can be changed thus allowing the filter to act as a bandstop or bandpass filter depending upon whether the switches are open or closed.

Abstract: The present invention relates to an arrangement for separating transmission and reception accomplished through one and same antenna (A) in a transceiver, said arrangement comprising a filter and a switching element (K) and being provided with a common port to be coupled to the antenna (A), a transmitter branch (TX) port (T) to be coupled to the transmitter of the transceiver and a receiver branch port (RX) port (R) to be coupled to the receiver of the transceiver, and in which, as a response to a control signal, the switching element couples operationally to the common port alternatively the transmitter branch port (T) and the receiver branch port (R). The arrangement comprises a filter (S.sub.T,S.sub.F,S.sub.1,S.sub.2) including transmission line resonators, said filter being provided with adaptation couplings to be coupled to the transmission line resonators and for accomplishing couplings between the transmission line resonators.

Abstract: In the housing of a filter realized with helix resonators, it is known to locate a coupling aperture in the partition between the resonators. According to the invention, the aperture in the partition is made so that outside the housing a milling cutter (33) is positioned at the point of the wall (31) of the housing where the partition (32) joins the wall of the housing. The longitudinal axis of the cutter extends in the plane of the partition. Then the cutter (33) is forced into the housing to a desired depth (H), whereby the cutter cuts an aperture in the partition open end at the housing surface, the aperture having a width equal to the width of the cutter and a height equal to the distance (H) the cutter was pushed. In this way it is easy to make coupling apertures also in extremely small sized filters, which are lower than 5 mm.

Abstract: The present invention relates to a radio frequency filter, comprising a block(1) of a dielectric agent and an insulation sheet (2) attached to a side surface thereof. From the top surface of the block to the undersurface, at least two holes (3,4,5) coated with a conductive agent extend. At least most of the surface of the body, with the exception of one side surface, as well as the surfaces of the holes have been coated with a conductive agent, whereby a transmission line resonator is produced for each hole. The surface of the insulation sheet (2) fixed against the uncoated side surface but not facing the block has also been coated with a conductive agent. The coupling pattern formed by the metallic electrodes is located between the opposite surfaces. The unevenness of the surfaces placed against each other and the defects in adjusting the pieces cause great divergence in the response curves of the filters.

Abstract: When the bandwidth of a duplex filter having a certain band-width, intended for a radio telephone, is increased by affecting the coupling between the resonator circuits, the stop band of the filter is at the same time deteriorated. According to the invention, the stop-band attenuation can be improved by coupling a surface-wave filter, coupled as a notch circuit, in parallel with one of the resonator circuits of the duplex filter.

Abstract: A filter, particularly suitable for radio frequency applications comprises a first filter which, in turn, comprises at least a pair of intercoupled resonators (RES1, RES2), and a SAW filter (SAW) which is coupled between the two intercoupled resonators so that a signal input to the filter at its input (IN) is coupled through the SAW filter to provide an output signal at its output (OUT). This provides a filter with all the advantages of a SAW filter, but with the ability to withstand the high power requirements of radio frequency applications. If three or more resonators are present in the first filter, then an amplifier can also be integrated in the filter. The SAW filter (and the amplifier if present) are inductively or capacitively coupled to the resonators depending upon the type of filter that is required.

Abstract: A filter (1) for filtering certain frequencies of an electric signal. The filter (1) comprises components (HX1-HX4) for forming the frequency response of the filter, and components (A,C) for accomplishing coupling and impedance matching. The filter is provided with a directional coupler (10) composed of two transmission lines (A,B), one of them being a coupling line (A) or an impedance matching line.

Abstract: A filter construction known in the art comprises at least a number of helix resonators (1) and an insulation material plate, the projections (2a) projecting from the rectangular lower part (2) whereof are provided inside the helix resonators and thus supporting them. The filter housing (6), defined by a cover (8) and the side walls, is provided with compartments, so that each compartment includes a helical resonator. As taught by the invention, at least two guides (71) projecting from the surface are extruded in the same phase as the compartment on the inner surface of the cover, wherebetween the tip part of the projection (2a) supporting the resonator enters when the filter is assembled. The guide can be a hemisphere or a rib-like bulge.

Abstract: The present invention relates to a resonator structure composed of two dielectric pieces. On the upper surface of a first piece (1) is provided a groove (7) extending across the entire surface and coated with an electrically conductive agent, said coating being at least in one end connected with an electrically conductive coating serving as a ground plane, so that the groove (7) forms a transmission line resonator. On the upper surface of the second piece (2) is provided a conductive strip (9) running in the middle of the surface, said strip forming a transmission line resonator. The pieces (1,2) are placed with the upper surfaces thereof against each other and attached to each other so that the groove (7) and the strip (9) are against one another in parallel, whereby the groove and the strip together form a resonator.

Abstract: The invention discloses a three-port filter being able to connect alternately a receiver and a transmitter to a common antenna in a ratio system operating by the time division principle. The first signal path between the first and the third ports comprises all resonators (R1, R2, R3, R4). The second port is connected to one (e.g. R3) of the resonators in the first signal path, whereby a first subset (R1, R2) of resonators lies between the first and the second ports, and a second subset (R3, R4) of resonators forming the signal path between the second and the third ports lies between the second and the third ports. The resonators of either subset are switchable resonators, whose resonance frequencies can be shifted between two frequencies by an external control (Control). At the first control value of the control (Control) the resonators of this subset pass the RF-signal substantially without attenuation, and at the second control value they strongly attenuate said signal.

Abstract: The body of a dielectric filter is provided with at least two parallel flanges (6) on either side of a side surface (4) having electrode patterns thereon, which project from the plane of the patterned side surface (4). The filter (1) is fastened, with the patterned side surface (4) facing downwards, to a base (9), for example a circuit board, which has, at least on one side, over an area the size of the filter, a conductive material which is in electrical contact with the coated surfaces of the filter. The filter is thus enveloped by a conductive layer on substantially all its sides.

Abstract: A helix resonator comprises a printed board (1) made of dielectric material, a resonator coil (2) having a high impedance end and a low impedance end and mounted on the printed board and formed by a conductor wound several turns to form a cylindrical coil, an electrically conducting cover (6) surrounding the resonator coil (2), and on the surface of the printed board a strip line (4) of electrically conducting material electrically coupled to the last or second last turn of the resonator coil (2) near the high impedance end.

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.