WO2006019302A1

WO2006019302A1 - Di electrical tunable resonance elements

Info

Publication number: WO2006019302A1
Application number: PCT/NO2004/000113
Authority: WO
Inventors: Leif Hjalmar Hansen
Original assignee: NOISELESS COMMUNICATION AS
Current assignee: NOISELESS COMMUNICATION AS
Priority date: 2004-04-23
Filing date: 2004-04-23
Publication date: 2006-02-23
Anticipated expiration: 2006-10-23

Abstract

It is described a resonator assembly comprising resonators where the resonator frequency is tuned such that a variable amount of di electric material changes the resonance frequency. This is obtained by changing the capacitance between the resonance element and the surrounding metal structure using a di electrical disc that is rotated up to 180 degrees around an axis.

Description

DI ELECTRICAL TUNABLE RESONANCE ELEMENTS Field of the invention

The present invention relates di electrical tunable resonance elements, that are used as the frequency setting unit and as filters in radio communication systems .

Technical background

When the di electrical resonance elements are used as filters, they are usually named as cavity filters. Cavity filters can be categorised in two main groups. One group is when cavity filters are used as band pass filter, i.e. used with a transmitter where one seeks to limit the frequency band to avoid that the transmitter affects receivers on close frequencies. The closer to the receiver frequency the transmit frequency is, the sharper filters needs to be used. The disadvantage using a sharp filter is that the attenuation at the transmit frequency increases as the relative distance between transmit and receive frequency is reduced. The same principle applies for receivers that are affected by a powerful transmitter on a close frequency.

The second group is where cavity filters are used as a notch filter, i.e. a transmit frequency passes the filter unaffected and maximum attenuation are applied to close frequencies to avoid that the noise level from the transmitter affects the receiving conditions on this frequency. The same applies when a receiver frequency shall filter a close transmitting frequency. The smaller distance between the frequencies, the larger will the noise level from the transmitter be. This means that the attenuation will need to be increased the closer the frequencies are. The existing cavity filters have a number of disadvantages. They are exposed to corrosion, as , oxidation of conducting through puts changes the characteristics of the cavity filter. Regular tuning of the filters will be required and there will be significant maintenance .cost for the end user.

The corrosion process does not only cause instability in the filter, but also degrades performance. The filter will loose its function with time, and will degrade the performance of the system configuration where the filters are included.

In cavity filter constructions where tuning of frequency is done such that the capacitance is changed by moving one of the conducting surfaces it is introduced inductance in the circuit due to the tuning shaft will function as a "coil" . This is a huge weakness and limits the cavity filters Q-value.

For cavity filters where tuning of the frequency is done by a mechanical control it is necessary to use a powerful control unit due to the requirement for precise adoption of the mechanical screw connected to the conducting surface in the filter.

The result is that the mechanical solution takes a lot of space and has a high cost, and at the same time exposed to corrosion, wear and tear as previously explained. Another disadvantage is that the mechanical solution prevents fast and frequent changes in frequency. The friction in the mechanical parts reduces the overall lifecycle of the filter.

Existing cavity filters has a limitation that the coupling factor must be tuned manually. The manual tuning requires either that the wire connections are turned with the tuning shaft or that slipring connectors are used with its disadvantages. Di electric tuneable resonance elements used as resonators are found in a number of designs. Ceramic cylindrical resonators are mechanically tuneable by changing the capacity using a screw mechanism that is turned in or out against the resonance element. If the screw mechanism is made ^out of metal it requires good electrical contact to the surrounding structure. If the screw mechanism consists of a di electrical material it will still be moved in or out against the resonance structure. Both designs have the same disadvantages as described for cavity filters.

Cavity (chamber) resonators, mostly used for microwave design, consists of a resonance chamber where the resonance frequency can be tuned with a screw mechanism as described above. The same disadvantages apply also for this design.

A common resonator is a ¹A or ¹A wave Coax resonator. The resonance frequency is fixed from the supplier and can only be changed by mechanically remove parts of the metal surface covering the ends of the resonator. This change can only be done once, and is critical as the resonator is of no use if the tuning fails.

Brief description of the invention

It is an object of the present invention to provide di electrical resonance elements that eases the problems mentioned above.

The invention presents a new principle for design of di electrical tuneable resonance elements. The new design is based on changing the amount of di electric material between fixed mounted conducting surfaces or a resonance structure. This can be done by changing the design and construction of di electrical resonance elements as defined in the appended patent claim 1. Several embodiments of the invention are possible, as covered in the appended patent claims 2-8.

Brief description of the drawings

The invention will now be described in reference to the appended drawings, in which:

Fig. 1 shows the main principle for the invention, where di electric material is turned maximum 180 degrees between the conducting surfaces with an eccentric tuning, that applies both to tuning of frequency and coupling factor

Fig.2 shows a different way of tuning based on the principle, using a centric tuning of the di electric material.

Detailed description of the invention

The invention solves the above described problems in the technical background with di electrical tuneable resonance elements:

a) Eliminates corrosion in the through puts of the conducting surfaces. b) Serial inductance will be reduced to the size of the conducting surfaces, which makes the invention applicable for extreme high frequencies. c) By changing the amount of di electric material for tuning frequency, can simplified control systems be introduced for tuning of frequency and coupling' factor. d) Reducing friction, wear and tear to a minimum, which improves the performance, increases stability and extends the lifecycle significantly. e) The di electric material is shaped as a disc and is turned around an axis centric or eccentric. Change of capacitance from minimum to maximum value is achieved by rotating the di electric material 180 degrees or less, depending of the shape of the di electric material and the metal surfaces. This design allows for a rapid and frequent change of capacitance. It is an advantage if the disc's shape is centric around the axis if extreme rapid changes in capacitance is required, due to the gravity forces.

The following description of the invention is related to the tuneable element used as cavity resonator (filter) .

Fig. 1 shows the main principle of the invention. The cavity filter consist of a cap (12), resonance element (3), signal connectors (15 and 16), tuning of coupling factor(7) , tuning of frequency(5) and eccentric tuneable di electric material (19) for frequency and (2 and 4) for coupling factor.

The frequency is tuned by rotating the shaft (5) up to 180 degrees, that changes the amount of di electric material (19) between the top of the resonance element (3) and the cap(12) to minimise the serial inductance. The shaft (5) consists of a non conducting material and is mounted eccentric on the disc (19) . That reduces the magnetic field from the resonator filter and the shaft(7)

Tuning of the coupling factor is done by turning the eccentric di electric discs (2 and 4) up to 180 degrees between the fixed conducting surfaces (21 and 22) by rotating the shaft (7) that is mounted with a mounting device(33) . The shaft (7) must be of a non conducting material with good high frequency parameters . There is a small hole in the resonance element which the shaft (7) is mounted through and the shaft is mounted through a hole in the wall of the cap(12) . The mounting device (33) for the shaft(7) is not critical for the technical solution. The shaft (7) pulls both di electric discs (2 and 4) in parallel that ensures a balanced tuning of coupling factor to the resonance element.

Fig.2 shows a different principle for tuning of the amount of di electric material (19) between the cap(12) and the top of the resonance element (3) . The di electric material consists of two parts (19 and 19a) with different di electric characteristic. The capacitance is tuned by rotating the disc(19) centric up to 180 degrees by turning the shaft (5) . At the top of the resonance element (3) there is a disc (3a) , that may be shaped as a carved 180 degrees sector with a 360 degrees top or one or more arbitrary shaped sectors . The disc (3) is sliding against the rotating di electric material (19) to minimise friction.

Fig.3 shows the invention where the principle of tuning of di electric resonator is described. The di electric resonator(3) is characterised by a specific resonance frequency and a high Q-value. The resonance frequency is adjusted torch the fixed metal surface(12) . More di electric material between the resonator (3) and the metal surface (12) will cause a lower resonance frequency in the resonator. Up to 20% change in frequency may be obtained.

The di electric resonator is mounted to a printed circuit board (PCB) (41, 42, 15 and 16) using a distance unit (6) . The PCB consist of coupling lines (15 and 16) that connects the surrounding circuit through the magnetic field to the di electric resonator(3) . (42) is the di electric material of the PCB, (41) is earth layer that is electrical connected to the surrounding cap(12) . Fig. 4 shows the invention where the resonator is a resonance chamber.

The figure shows a filter with di electric tuning of resonance frequency by a disc consisting of two halves (19 and 19a) , that have different di electrical constant, mounted to a shaft (5) that is rotated up to 180 degrees. The disc (19 and 19a) is mounted in a slot (8) in the housing(12) where parts of the disc is lowered into the resonance chamber(51) . The amount of di electric material changes the resonance frequency. The probes (15 and 16) connects the resonance chamber to the surrounding electric structure.

Fig. 5 shows the invention where the resonator is a coax resonator.

The resonator is normally designed either as a M wave or a ^XA wave unit. The resonator consist of an inner metallic tube(3) with a connector(3a) , a di electric material (51) that between the inner tube (3) and the outer conducting surface (12) .

The connector(3a) may in certain circumstances be connected to both ends of the resonator. A di electric disc consisting of two halves (19 and 19a) with different di electrical constant mounted to a shaft (5) that rotates up to 180 degrees. The disc(19 and 19a) is mounted in a slot (8) where parts of the disc is lowered into the di electrical material (51) . The amount of di electrical material into the slot (8) changes the resonance frequency.

An alternative tuning methode for this kind of resonator could be di electrical screws that is screwed inn from the end surfaces .

Claims

Patent claims

1. Resonator assembly comprising resonators where the resonator frequency is tuned c h a r a c e t e r i z e d such that a variable amount of di electric material (19) changes the resonance frequency such that the capacitance between the surfaces (3 and 12) varies using a di electrical disc (19) that is . rotated by a shaft (5) up to 180 degrees.

2. Resonator assembly as claimed in claim 1, comprising resonators where coupling factor is tuned c h a r a c t e r i z e d of a variable amount of di electrical material (2 and 4) changes the coupling factor between the fixed metal surfaces (21 and- 22) and the resonator element (3) .

3. Resonator assembly as claimed in claim 1 and 2, c h a r a c t e r i z e d i n that said resonator element is a typical M wave or % wave resonator.

4. Resonator assembly as claimed in claim 1 and 2, c h a r a c t e r i z e d i n that said resonator ^ element is a helix coil.

5. Resonator assembly as claimed in claim 1 and 2, c h a r a c t e r i z e d i n that said resonator element is a di electric resonator.

6. Resonator assembly as claimed in claim 1 and 2, c h a r a c t e r i z e d i n that said resonator ^% element is a transmission line.

7. Resonator assembly comprising a coax resonator as claimed in claim 1, c h a r a c t e r i z e d i n that the amount of di electric material inserted in the resonator element changes the resonator frequency.

8. Resonator assembly comprising a chamber resonator as claimed in claim 1, c h a r a c t e r i z e d i n that the amount of di electrical material inserted in the resonance chamber changes the resonance frequency.