Lk Products Oy

Adc Solitra Oy

Aimo Turunen

Heli Jantunen

Pauli Nappa

Tapio Takalo

Resonator resonant frequency tuning

Lumped-constant resonator structure and method for adjusting it

Stripline resonator structure formed on upper and lateral surfaces of

Coaxial resonator and filter having a module block construction

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. The provision of these control circuits allow transmission zeroes to be selected in situ, rather than solely during manufacture.

Filter having an electromagnetically tunable transmission zero

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.

Selectable bandstop/bandpass filter with switches selecting the

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.

Saw notch filter for improving stop-band attenuation of a duplex filter

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.

Filter having resonators coupled by a saw filter and a duplex filter

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.

Resonator structure having a strip and groove serving as transmission

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.

Duplex filter operating as a change-over switch

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.

Dielectric filter

Harmonic frequencies of a ceramic filter (1) can be efficiently attenuated by placing in a hole (2; 3) of a first and/or last resonator a conductive rod (7; 7'), on which disk-like insulating plates (9, 10, 11, 12; 9', 10', 11', 12') are provided in spaced relationship along the length of the rod. The harmonic filter thus formed is a low pass filter, comprising transverse capacitances formed by the insulating plates and longitudinal inductances formed by the rod portions between the plates. Coupling between the harmonic filter and the resonators of the main filter takes place at the upper end of the rods (7, 7').

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.

Ceramic band-stop filter

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.

Temperature compensated dielectric filter

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.

Growing community of inventors

Oulu, Finland

Aimo Turunen