WO2006059159A1 - Tunable or re-configurable dielectric resonator filter - Google Patents
Tunable or re-configurable dielectric resonator filter Download PDFInfo
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- WO2006059159A1 WO2006059159A1 PCT/GB2005/050227 GB2005050227W WO2006059159A1 WO 2006059159 A1 WO2006059159 A1 WO 2006059159A1 GB 2005050227 W GB2005050227 W GB 2005050227W WO 2006059159 A1 WO2006059159 A1 WO 2006059159A1
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- filter
- dielectric resonator
- cavity
- dielectric
- deformable
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P7/00—Resonators of the waveguide type
- H01P7/10—Dielectric resonators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/207—Hollow waveguide filters
- H01P1/208—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure
- H01P1/2084—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure with dielectric resonators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/207—Hollow waveguide filters
- H01P1/208—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure
- H01P1/2084—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure with dielectric resonators
- H01P1/2086—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure with dielectric resonators multimode
Definitions
- the present invention relates to a tunable or re-configurable dielectric resonator filter, to a filter comprising a plurality of such filters, to an electronic device comprising the filter, to a method of filtering different frequency bands from an input frequency spectrum, to a method of tuning a dielectric resonator filter, and to a piezoelectrically tuneable microwave filter.
- DRs dielectric resonators
- Q resonator quality factors
- a dielectric resonator is a device in which a piece of high dielectric constant (>1) material, commonly known as a puck, is placed within a conducting enclosure that has an input and an output for an electrical signal at microwave frequencies (typically between about 300MHz and 3GHz).
- the puck is often supported away from the walls of the enclosure by a hollow tube of low dielectric constant material.
- Application of the electrical signal causes the DR to resonate at a number of different modes.
- Each mode has different resonant frequency at which most of the electromagnetic energy is stored within the DR; the arrangement of the electric and magnetic fields of each mode is also different.
- Which mode has the lowest resonant frequency (the fundamental mode) is determined by the dimensions of the puck and by the external boundary conditions.
- the external boundary conditions may include tuning screws, for example, that project into the enclosure for perturbing the electromagnetic field around the puck, thereby changing the fundamental mode with the lowest resonant frequency.
- HE and HEM refer to the same resonance mode.
- n 0 as there are no electric or magnetic fields in the axial (z) direction.
- the third index g is used to denote the number of half- wavelength variations in the axial direction.
- ⁇ or is omitted entirely
- the hybrid modes are so-called because non-vanishing axial (z) components of the electric and/or magnetic fields are present.
- Microwave filters have been made that use DRs.
- the filter function is achieved by using more than one DR and coupling the energy between them (e.g. with irises or slots between each cavity).
- Each DR in the filter is tuned to a different resonant frequency. With two or more such DRs, each tuned to a different but closely spaced frequency, a filter-like function can be obtained.
- the number of resonant frequencies used to obtain the filter function is known in the art as the number of "poles". As explained below, it is not always the case that the number of poles is equal to the number of DRs used in the filter.
- each degenerate mode can then be independently tuned (e.g. with an appropriately aligned tuning screw respectively) to separate the two resonant frequencies and provide a filter function.
- the number of poles of the filter is two, but only one DR is present.
- DRs that employ two modes are known in the art as "dual mode" DRs. It is possible to couple the energy between more than one dual mode DR to obtain e.g. a four-pole, six pole, etc. filter. The more poles that are used the larger the pass band of the filter can be.
- DR filters The tuning of DR filters is a very difficult task.
- the shapes, sizes and arrangement of inter alia: the enclosure, the puck, the support for the puck, and if needed, the shape and size of the coupling slot(s); are never ideal.
- the puck is never a perfect cylinder (or whatever other shape is used).
- the resonant (or centre) frequency of each DR is dependent on these shapes, sizes and positions (assuming materials are kept the same). Therefore each filter that is manufactured must be tuned to ensure that the filter has the desired characteristics e.g. bandwidth, insertion loss and return loss. All of the poles of the filter must be tuned correctly to achieve this.
- EP 1 041 663 discloses a four pole filter comprising two dielectric resonators each operated in the dual mode.
- Each dielectric resonator has pair of tuning screws for tuning the resonance frequency of each of two orthogonalHEM in resonant modes respectively.
- the coupling between these modes is provided by a third tuning screw located midway between the first two at an angle 45° thereto.
- the two dielectric resonators are coupled by cruciform shape irises.
- Such a filter is only adjustable post-manufacture with extreme difficulty.
- some element of re- configurability is desirable.
- the pass band of the filter could be adjusted post manufacture whilst maintaining the other properties of the filter (e.g. insertion loss, return loss, filter shape - Chebyshev, elliptic, etc.) substantially the same.
- the re-configuration could be activated remotely i.e. without the need for an operative to perform the reconfiguration manually, and for the re-configuration to take place quickly.
- a microwave filter e.g. in a base station
- UMTS Universal Mobile Telecommunications System
- Microwave filters are used to extract these channels from the frequency spectrum. If either of the channels becomes saturated it would be useiul if the infrastructure could be re-configured to switch to a new 5MHz channel. This would necessitate inter alia manual adjustment of the DR microwave filter in the base station to filter the new channel from the spectrum.
- the present invention is based upon the insight by the applicant that it is possible to re-configure dielectric resonator microwave filters remotely, quickly and easily, substantially without change in the electrical characteristics of the filter.
- a dielectric resonator filter having at least two poles for filtering a frequency band from an input frequency spectrum
- which filter comprises (i) a body formed of electrically conductive material, which body defines a cavity therein; (ii) a dielectric resonator element enclosed in said cavity, ( ⁇ i) a deformable member located outside said cavity, and (iv) a metal member located within said cavity that is connected to said deformable member, the arrangement being such that, in use, said deformable member is deformable to move said metal member toward and/or away from said dielectric resonator element to effect adjustment of said frequency band.
- the filter may be a microwave filter for operation in the microwave portion of the spectrum e.g.
- the present invention provides :- i. The possibility to decrease the size and weight of a filter by using dual mode resonators; ⁇ . The possibility to control the type of the filter response; ⁇ i. Cost effectiveness and speed of manufacture - the present invention uses only one perturbing member for tuning purposes; iv. Following manufacture the filter is quickly re-configurable (over e.g. about 10 frequency bands at 2GHz) to operate in a different frequency band substantially without loss of filter characteristics.
- a dielectric resonator filter having at least two poles for filtering a frequency band from an input frequency spectrum
- which filter comprises (i) a body formed of electrically conductive material, which body defines a cavity therein; (ii) a dielectric resonator element enclosed in said cavity, and (iii) a perturbing member, the arrangement being such that, in use, said dielectric resonator element resonates in a dual mode in which there are at least two modes having a respective degenerate resonant frequency, and said perturbing member is moveable into and out of said cavity so as to adjust simultaneously the spacing between said at least two degenerate resonant frequencies and the coupling of energy between said at least two modes.
- the invention also provides a tunable filter based on at least one dielectric resonator which is piezoelectrically controlled and in which the fundamental is the dual generated HEM 11 mode.
- the invention further provides an improved filter comprising at least one dielectric resonator in which there is a perturbing member to control filter response type (elliptic or a Chebyshev type characteristics) and a deformable member to adjust the filter frequency band, for example, by adjustment of a voltage.
- the fundamental mode of the dielectric resonator may be the dual generated HEM 11 mode.
- ⁇ (n-90°+45°)
- the perturbing member provides feedback between the input/output loops, which results in an elliptic characteristic of the filter response.
- the filter has a Chebyshev type response.
- movement of said deformable member effects a shift of said frequency band from a lower to a higher frequency band, or vice versa.
- One advantage of the present invention is that one or more filter characteristic of said filter remains substantially unaffected by said adjustment.
- said cavity in which resonance takes place, has the same dimensions following said adjustment. This helps to make the filter more robust and more reliable.
- said deformable element is deformable in response to a signal, whereby said adjustment may be made remotely from said filter.
- said deformable element is deformable upon application of a voltage.
- said deformable element is able to effect an overall movement of said metal member from a point about 200 ⁇ m away from said dielectric resonator element to a point substantially in abutment with part of said dielectric resonator element. In one embodiment this relatively small movement is able to effect movement of the filtered frequency band by 400MHz at 2GHz, substantially without degrading the filter response.
- said deformable member is connected to said metal member via an arm, which arm is slidable in use through an aperture in said body.
- said deformable member comprises a piezoelectric bimorph.
- said piezoelectric bimorph is held substantially fixed relative to said body by a top cap. This helps to ensure that any deformation is translated into movement of the metal plate.
- said filter is configured such that in use, said at least two poles are provided by a dual mode in which at least two degenerate resonant frequencies are supported on one dielectric resonator element. This helps to reduce the physical size of the filter and enables a filter function to be achieved using only one dielectric resonator element if desired.
- said filter further comprises a perturbing member that is moveable into an out of said cavity for simultaneously adjusting the energy coupled between said at least two degenerate resonant frequencies and the spacing between the resonant frequencies thereof.
- said perturbing member is positioned in a part of said cavity in which at each point the amplitude of the respective electric field due to said at least two degenerate modes is substantially the same. This helps the perturbing member to adjust the at least two resonant degenerate frequencies simultaneously. In one embodiment there is only one perturbing member per dielectric resonator element.
- the line may defined by the axis of an input microstrip for example with the angle ⁇ being measure in an anti-clockwise sense from said line to an axis of said perturbing member.
- said perturbing member is positioned to substantially maintain symmetry in plan view between an input and an output to said dielectric resonator element.
- said perturbing member comprises an adjustable screw for movement into and out of said cavity.
- said filter further comprises a dielectric substrate defining a lower limit of said cavity.
- the dielectric substrate extends to the walls of the cavity.
- said dielectric substrate comprises a metallised side and a dielectric side, said dielectric resonator element supported on said dielectric side
- the filter further comprises a pair of microstrip lines providing an input and an output to said filter.
- said pair of microstrip lines is substantially orthogonal to one another to take advantage of the orthogonal electric fields in a dual mode for example.
- said metal member comprises a plate or plate-like shape.
- the metal member may comprise, or consist of, a metal.
- each dielectric resonator element provides a two pole filter.
- each dielectric resonator element resonates in a single mode.
- dielectric resonator elements each operable in a dual mode to provide a six-, eight- or more pole filter.
- the filter is configured such that the lowest resonant frequency is provided by a Hybrid Electric and/or Magnetic mode.
- the HEM 11 mode is preferred as spurious frequencies (i.e. resonant frequencies of other modes) are much higher and therefore the filter has a better response characteristic.
- a filter comprising a plurality of filters as set out above, which filter comprises a body defining a plurality of cavities linked so as to provide coupling between a dielectric resonator element in each cavity and a path for a microwave signal through said filter.
- the coupling between said cavities is provided by an iris formed in the conductive wall therebetween, the size of said iris controllable by a tuning screw.
- said metal members are independently controllable for example by different voltages supplied from a power source.
- an electronic device comprising a filter as aforesaid.
- step (b) is carried out by transmitting an adjustment signal to said filter from a location remote therefrom.
- step (c) if necessary, repeating step (b) until desired filter characteristics are substantially met.
- a piezoelectrically tunable microwave filter based on one or more dielectric resonators in which the fundamental resonant frequency is the dual generated HEM 11 mode.
- tuning is provided by a piezoelectric unit placed outside a resonator cavity of said filter.
- Fig. 1 shows the distribution of the electric field HEM 11 simulated using Ansoft HFSS v.8.0
- Fig. 2a is a graph of the resonance frequency (y-axis) of the dielectric resonator in Fig. 1 versus gap size (d) (x-axis);
- Fig. 2b is a graph of quality factor of the dielectric resonator (y-axis) in Fig. 1, versus gap size (d) (x-axis);
- Fig. 3a is a schematic side cross section of a first embodiment of a filter according to the present invention
- Fig. 3b is a plan view of the filter of Fig. 3a;
- Fig. 4a is a graph of the frequency response (y-axis) versus frequency (x-axis) for the filter of Figs. 3a and 3b
- Fig. 4b is a graph of the frequency response (y-axis) versus frequency (x-axis) for the filter of Figs. 3a and 3b showing how the pass band can be shifted;
- Fig. 5a is a graph of the frequency response (y-axis) versus frequency (x-axis) for the filter of Figs. 3a and 3b (with a puck made from different dielectric material);
- Fig. 5b is a graph of the frequency response (y-axis) versus frequency (x-axis) for the filter in Fig. 5a showing how the pass band can be shifted;
- Fig. 6a is schematic side cross section of a second embodiment of a filter according to the present invention.
- Fig. 6b is a plan view of the filter of Fig. 6a;
- Fig. 7a a graph of the frequency response (y-axis) versus frequency (x-axis) for the filter of Figs. 6a and 6b
- Fig. 7b is a graph of the frequency response (y-axis) versus frequency (x-axis) for the filter in Figs. 6a and 6b showing how the pass band can be shifted
- Fig. 8 is a schematic plan view of a third embodiment of a filter according to of the present invention.
- a computer simulation of the distribution of the electric field of a dielectric resonator filter tuned to operate in the HEM 11 mode is shown.
- the filter comprises a resonator cavity (not shown) having a grounded metal substrate (14) on which is supported a cylindrical dielectric resonator DR element (13).
- a metal member in the form of a disc (11) is disposed adjacent the DR 13 with an air gap d (12) therebetween.
- the metal disc is also cylindrical in shape and has a diameter of 14mm (similar to the diameter of the puck (I)) and a thickness of lmm.
- the metal disc (11) is mounted on a brass rod (10) co-axially with the longitudinal axis of the DR 13 permitting the metal disc (11) to move axially toward and away from the upper surface of the DR 13.
- the rod (10) may be constructed of other materials e.g. plastics, ceramic, but preferably from a material with a low thermal expansion coefficient e.g. invar.
- the simulation was performed using Ansoft HFSS v 8.0.
- the swirling part of the electric field near the centre of the DR 13 is weaker than the electric field that is oriented substantially parallel to the longitudinal axis of the DR 13.
- a cylindrical chamber (2) is defined by an electrically conductive material, in this case silver plated aluminium, comprising a base or housing (2b) and a cover (2a) which are in electrical contact with one another.
- the cover (2a) fits over the base in a similar fashion to a lid; in an alternative embodiment the base (2b) and cover (2a) may comprise flat surfaces for abutment with one another and held together by bolts.
- the base (2b) comprises a bore passing from one side of the base to the other.
- a ledge is provided partway along the length of the bore that supports a dielectric substrate (3) made from a low loss dielectric, in this case aluminium oxide.
- the dielectric substrate (3) comprises a metal- coated lower surface that contacts the ledge; the dielectric substrate can be about 0.5- 2.0mm thick and the metal-coated lower surface is about 6 ⁇ m thick comprising a 4 ⁇ m thick base layer of copper covered with a 2 ⁇ m thick covering layer of gold to inhibit oxidisation of the copper.
- An upper surface of the dielectric substrate (3) supports a dielectric resonator element or puck (1) that is of cylindrical shape.
- the base (2b), cover (2a) and dielectric substrate (3) define a cylindrical cavity (13).
- the top and bottom covers (2a) and (2b) are separable to enable manufacture of the filter.
- the cover (2a) comprises an upwardly projecting annular support provided with a ledge on its inner surface.
- an aperture accommodates an arm which in this case is a metal rod (5) (that in this embodiment is made from brass, but could be any of the materials mentioned in connection with the metal rod (10) above) for sliding movement along its longitudinal axis.
- a lower end of the metal rod (5) is disposed within the cavity (13) and mounts a metal member in this embodiment metal tuning disc (4) adjacent and substantially co-axial with the longitudinal axis of the puck (1).
- the metal tuning disc (4) is made from copper in the shape of a flattened cylinder of 14mm diameter by lmm thick.
- the diameter of the metal tuning disc (4) is substantially the same as the diameter of the puck (1), although this is not essential.
- the lower surface of the metal tuning disc (4) (which is substantially flat) is held by the metal rod (5) at a distance d and substantially parallel with an upper surface of the puck (1) (which is also substantially flat).
- An upper end of the metal rod (5) is disposed outside the cavity (13) and is connected to the centre of a deformable element in this embodiment a circular piezoelectric actuator (6).
- the actuator (6) was soldered to the cover (2a), but it might be glued or fixed in any other way that provides a firm connection to the cover (2a).
- the actuator (6) has a diameter of 25mm and rests on the ledge in the upwardly projecting annular support of the cover (2a); it is confined to the ledge by a top cap (7), made of plastics i.e. a non-conducting material, that screws into the upwardly projecting annular support and holds the actuator (6) on the ledge.
- the piezoelectric actuator (6) is a circular bimorph plate defined by two piezoelectric plates cemented together in such a way that an applied voltage causes one to expand and the other to contract. Suitable circular bimorph plates can be obtained from Morgan Electroceramics, USA. Thus, the bimorph plate bends in proportion to the applied voltage.
- the actuator (6) is connected to an external variable power source which can provide a DC voltage from zero Volts to several hundreds of Volts. When a voltage is applied, the piezoelectric actuator (6) bends accordingly (restrained in the upward sense by top cap (7)) and moves the metal rod (5) and metal tuning disc (4) either towards or away from the puck (1), thereby changing the air gap d therebetween, and as explained below, the frequency band of the filter.
- FIG. 3b there is an input connector (Ha) which is coupled with the puck (1) by an input microstrip line (10a) formed onto the top side of the dielectric substrate (3).
- the microstrip line runs from the input connector (Ha) to the dielectric resonator element (1).
- output microstrip line (10b) is output microstrip line (10b), formed on the top side of the dielectric substrate (3), orthogonal to the input microstrip line (10a).
- the output microstrip line (10b) runs from the dielectric resonator element (1) to the output connector (1 Ib).
- the fundamental mode of the filter in Fig. 3 a and 3b is the dual generated HEM 11 mode i.e. where there are two degenerate modes and therefore two resonant frequencies available to obtain a filter function.
- the applicant has realized that only one perturbing member (in this embodiment an adjustable screw (9)) is needed to perform both a tuning and a coupling function.
- the adjustable screw (9) is positioned so that its axis lies in the cavity (13) where at each point the amplitude of the electrical field of each degenerate mode is expected to be the same or substantially the same. This may be determined having regard to the electric field patterns of the modes excited in the cavity (13).
- the adjustable screw (9) is positioned to maintain symmetry between the input microstrip (10a) and output microstrip (10b); otherwise the perturbation it provides on the electromagnetic fields will have an asymmetric effect on each degenerate mode. Accordingly the best positions for the adjustable screw (9) with one dielectric resonator element (1) as shown in Fig. 3b is at 45° or 225° measured with respect to the line defined by the longitudinal axis of the microstrip 10a.
- the adjustable screw (9) may be turned so as to move into or out of the cavity to set the bandwidth (i.e. the frequency between the resonant peak of each degenerate mode) of the filter for the intended application. Once set, the adjustable screw (9) does not need to be adjusted again.
- a tunable or re-configurable four-pole DR filter according to the second embodiment of the present invention is shown.
- the filter uses two dielectric resonators arranged so as to operate in the dual mode HEM 11 .
- the construction of each DR is generally similar to the embodiment shown in Figs. 3a and 3b. However, the energy must be coupled from DR to the other if the four pole filter is to work.
- a body (2) made of an electrically conductive material in this embodiment aluminium comprises a base and a cover which are in electrical contact with one another. Two bores inside the base are partially separated by a conductive wall (14) to two define cylindrical cavities (13a and 13b respectively).
- a dielectric resonator element or puck (Ia and Ib) is located in each cavity (13a) and (13b) supported by dielectric substrates (3a and 3b).
- the coupling between dielectric resonator elements is provided by an iris (15) formed in the conductive wall (14); the coupling can be adjusted by a tuning screw (12) that is disposed to move up and down with respect to the conductive wall (14) to change the size of the iris (15).
- a metal member that in this embodiment is a metal tuning disc (4a and 4b) is suspended above the dielectric resonators (Ia and Ib) at a distance d (8) respectively. Similar to Fig. 3a a metal rod (5a and 5b) connects each metal tuning disc (4a and 4b) to a circular piezoelectric actuators (6a and 6b) which are placed outside cavities (13a and 13b). The actuators (6a and 6b) are held in place by a respective top cap (7a and 7b) to the top cover of the chamber (2). Each top cap (7a and 7b) comprises a non-conductive material, in this embodiment PTFE.
- Each deformable element that in this embodiment is a piezoelectric actuator (6a and 6b) is a circular bimorph cell defined by two piezoelectric plates cemented together in such a way that an applied voltage causes one plate to expand and the other to contract. Thus, each bimorph cell bends in proportion to the applied voltage.
- Each actuator (6a and 6b) is connected to a separate external variable power source which can provide a DC voltage from zero Volts to several hundreds of Volts. When a voltage is applied, each piezoelectric actuator (6a and 6b) bends accordingly and moves the respective metal rod (5a and 5b) and metal tuning disc (4a and 4b) either towards or away from the respective puck, thereby changing the air gap d therebetween.
- each actuator (6a and 6b) may respond differently to the same applied voltage. Accordingly it may be necessary to calibrate the actuators at point of manufacture by determining how much movement is achieved for a given applied voltage. When reconfiguring the filter during in use it may then be necessary to apply a different voltage to each actuator (6) to obtain the same amount of movement of each metal tuning disk (4a and 4b) so that the electrical characteristics of the filter are substantially unaffected.
- a signal is applied into the filter from an input connector (Ha) that is coupled with the first dielectric resonator by an input microstrip line (10a) formed onto the top side of the dielectric substrate (3a).
- the microstrip line (10a) runs from the input connector to the first dielectric resonator (Ia).
- the first resonator (Ia) is coupled with the second/output resonator (Ib) by an iris (15) formed in the conductive wall (14).
- the coupling between cavities is controlled by tuning screw (12).
- output microstrip line (10b) For coupling the resonant energy out of the filter, there is output microstrip line (10b), formed on the top side of the substrate (3b), and turned by 180° to the input microstrip line (10a)
- the output microstrip line (10b) runs from the second/output dielectric resonator (Ib) to the output connector (l ib) which is positioned on the opposite (in respect to the input connector) wall.
- the fundamental mode of both dielectric resonators is the dual generated HEM 11 mode i.e. where there are two degenerate modes and therefore two resonant frequencies available to obtain a filter function.
- an adjustable screw (9a and 9b) per dielectric resonator is used.
- ⁇ 45° in respect to the input and output connectors, respectively.
- the input to dielectric resonator element Ia is the microstrip 10a and a "virtual" output is provided by the iris (15); the axis of the iris (15) lies substantially perpendicular to the axis of the microstrip (10a).
- the output (l ib) lies perpendicular to the virtual input provided by the iris (15), although it could have been placed 180° from the position shown in Fig. 6b.
- an adjustable screw (9a and 9b) is required per dielectric resonator element to set the filter bandwidth and the degree of coupling between the degenerate modes.
- the adjustable screws also provide feedback between the input/output loops, which results in elliptic characteristics of the filter response as presented in Fig. 7.
- the input (Ha) and output (1 Ib) may be located on the same side of the body (2), although for easy access to the adjustable screws (9a and 9b) the arrangement shown in Fig. 6b is preferred.
- Fig. 8 shows a tunable or re-configurable eight-pole filter based on four dielectric resonator elements according to a further embodiment of the present invention.
- the filter uses two dielectric resonator elements arranged so as to operate in the dual mode HEM 11 .
- the construction of each DR is generally similar to the embodiment shown in Figs. 3a, 3b, 6a and 6b. However, the energy must be coupled from one DR to the next if the four pole filter is to work.
- This embodiment presents a possible arrangement of dielectric resonators to form an eight pole filter using the principle of the invention.
- the arrangement of the input, outputs and perturbing members (e.g. adjustable screw) of each dielectric resonator element follows that discussed above.
- dielectric resonators Ia - Id
- the filter comprises a base and a cover, both made of an electrically conductive material, and both of which are in electrical contact with one another.
- Four bores inside the base are divided by conductive walls to form four cylindrical cavities (13a - 13d).
- the coupling between dielectric resonator elements is provided by irises formed in the conductive walls.
- Four metal tuning discs are adjustable by a respective deformable element, in this embodiment each comprising a piezoelectric actuator, and each metal disc is suspended above a respective dielectric resonator element at a distance d.
- the piezoelectric actuators are used to tune or re-configure the filter frequency band.
- Each piezoelectric unit may be controlled separately. As described above in connection with Figs. 6a and 6b each piezoelectric actuator may need to be controlled with a different voltage to obtain the same degree of movement of all of the metal tuning disks when re-configuring the filter.
- a signal is applied into the filter from an input connector (1 Ia) and coupled with the dielectric resonator by an input microstrip line (10a) formed onto the top side of the dielectric substrate (3a).
- the microstrip line runs from the input connector to the first dielectric resonator (Ia) (bottom left Fig. 8).
- the first dielectric resonator (Ia) is coupled with the second (Ib) (top left Fig. 8), the second is coupled to the third (Ic) (top right Fig. 8); the third is coupled to the fourth resonator (Id) (bottom right Fig. 8); and the fourth is coupled back to the first; by irises formed in the conductive walls.
- output microstrip line (10b) For coupling the resonant energy out of the filter, there is output microstrip line (10b), formed on the top side of the substrate (3b), and parallel to the input microstrip line (10a).
- the output microstrip line (10b) runs from the fourth dielectric resonator (Id) to the output connector (1 Ib) which is parallel to the input connector.
- the fundamental mode of all dielectric resonators is the dual generated HEM 11 mode.
- the cavity (13) had a diameter 35mm and height 20mm and was silver-plated.
- a metal tuning disc (4) with a diameter substantially equal to the diameter of the puck (1) was suspended over the puck with a small gap d.
- a circular piezoelectric bimorph (6) with diameter 25mm and thickness lmm was used for driving the metal disk along axis of the puck (1). The downward displacement at the centre of the bimorph was ⁇ 140 ⁇ m under 300V bias voltage.
- a signal of between 1 and 1OW power was used to test the filter.
- the filter performance did not change noticeably between different input powers.
- Coupling between the input and output ports and the puck (1) was maintained by microstrip lines patterned on the top side of the dielectric substrate (3).
- the coupling between the puck (1) and the microstrip lines was achieved by placing the puck (1) in close proximity to the microstrip line.
- the puck (1) may be placed next to the microstrip line or even on top of the microstrip line.
- the puck was placed such that approximately lmm of the end of the microstrip lines were underneath the puck (1) providing the coupling of the resonator with input and output ports.
- the fundamental resonance mode with the lowest frequency was the dual degenerate mode HEM 11 .
- the internal coupling between the pair of resonator modes was facilitated by the adjustable screw positioned at an angle 45° of the input connector.
- the coupling between modes was defined by the distance between the circumference of the resonator and the screw face; this distance must be determined for every filter by adjusting the screw until the desired filter response is seen e.g. on a network analyser. It was observed that the first spurious mode of the resonator was at -IGHz higher than the frequency of the fundamental mode (2.06GHz).
- the distribution of the electric field HEM 11 is shown in Figure 1.
- the dependencies of the resonance frequency and quality factor of the dielectric resonator with HEM 11 mode on the gap between the top flat surface of the puck (1) and metal tuning disc (4) are shown in Figures 2a and 2b.
- Fig. 2a it will be noted that changing the distance between the lower surface of metal tuning disc (4) and the upper surface of the puck (1) only a very small amount i.e. between O ⁇ m and about 170 ⁇ m effected a change in the centre frequency of the filter from about 2.06GHz to 2.46GHz i.e. providing a re-configuration range of 400MHz at 2GHz. It was very surprising that tuning could be performed over such a wide frequency range for such a small amount of movement of the metal tuning disc (4). Referring to Fig. 2b it is also seen that for approximately the same range of d the Q factor of the filter changes only from about 1700 to 2200.
- the bandwidth ( ⁇ f / f) for IdB level was ⁇ 0.3%.
- Applying a dc bias up to 300V to the piezolelectric actuator (6) resulted in altering of the distance between top surface of the puck and metal tuning disc from about 50 ⁇ m to 180 ⁇ m, a central frequency tuning ( ⁇ F //) of ⁇ 8% was achieved as shown in Fig. 5b.
- the insertion losses in the whole tuning range were below ⁇ -0.5 dB, while the return losses were less than -20 dB.
- the return losses are less than -15 dB.
- a filter employing the present invention has wide application, for example: military/commercial radars, cellular base stations, satellite communication systems, automotive anti-collision radars, frequency selective surfaces, etc.
- any suitable dielectric material may be used to form the dielectric resonator element, for example Ba-Mg-Ta-O and Ca-Ti-Nd-Al-O.
- the dielectric resonator element may be made in any shape that substantially matches the shape of the cavity (or vice versa) in which it is to be used, for example: cuboid, spherical, hemi-spherical or cruciform. For example in a cuboid embodiment there may be three degenerate resonant frequencies present. These may be coupled and adjusted in a similar way to that described above, except that more than one surface of the cuboid will need to have an adjacent metal member to provide the re-configuration function.
- the dielectric resonator element may be substantially any size, although the size will depend on the relative dielectric constant of the material and the desired frequency of operation.
- the distance between the outer surfaces of the dielectric resonator element and the cavity walls should be such that the wall losses introduced are kept as low as is feasible.
- This distance is usually at least approximately the diameter of the dielectric resonator element (assuming it is circular in plan view), but can be greater. However, this distance can be less than the diameter of the dielectric resonator element if a more compact design is sought.
- the cavity may also be any shape that substantially matches that of the dielectric resonator element.
- the invention can also employ either the HEM 12 or HEM 21 mode, although other hybrid modes are not excluded.
- other resonant modes known as spurious frequencies
- spurious frequencies are closer to the resonant frequencies of interest. This can have a detrimental effect on the filter function.
- the deformable element may comprise any device is able to effect a controlled movement of the arm.
- the deformable element may comprise piezo- mechanical material, a micro electro-mechanical system (MEMS), a magnetostrictive material or a bi-metallic strip
- the metal member may comprise any suitable metal, for example copper, brass or aluminium. It is preferable if the surface is plated (e.g. with silver or gold), and/or is polished.
- the shape of the metal member (e.g. in plan view) should substantially match the side of the dielectric resonator element to which it will be brought adjacent; it is not necessary however for the metal member to be the same size (e.g. diameter) as the dielectric resonator element. It may be smaller, larger or the same size. It has been found however that a size of metal member ⁇ 10% of the size of the surface of the dielectric resonator element produces good results.
- the thickness of the metal member should be sufficient to hold the desired shape, and may be between about 2mm and 4mm for example.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0712744A GB2436493A (en) | 2004-12-01 | 2005-12-01 | Tunable or re-configurable dielectric resonator filter |
US11/792,180 US20080129422A1 (en) | 2004-12-01 | 2005-12-01 | Tunable or Re-Configurable Dielectric Resonator Filter |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0426350.5 | 2004-12-01 | ||
GBGB0426350.5A GB0426350D0 (en) | 2004-12-01 | 2004-12-01 | Tuneable dielectric resonator |
Publications (1)
Publication Number | Publication Date |
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WO2006059159A1 true WO2006059159A1 (en) | 2006-06-08 |
Family
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/GB2005/050227 WO2006059159A1 (en) | 2004-12-01 | 2005-12-01 | Tunable or re-configurable dielectric resonator filter |
Country Status (3)
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US (1) | US20080129422A1 (en) |
GB (2) | GB0426350D0 (en) |
WO (1) | WO2006059159A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2009000862A2 (en) * | 2007-06-26 | 2008-12-31 | Radiocomp Aps | Tuneable rf filters and methods thereof |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
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US20090088105A1 (en) * | 2007-09-28 | 2009-04-02 | Ahmadreza Rofougaran | Method and system for utilizing a programmable coplanar waveguide or microstrip bandpass filter for undersampling in a receiver |
US8040007B2 (en) | 2008-07-28 | 2011-10-18 | Direct Drive Systems, Inc. | Rotor for electric machine having a sleeve with segmented layers |
US8598969B1 (en) * | 2011-04-15 | 2013-12-03 | Rockwell Collins, Inc. | PCB-based tuners for RF cavity filters |
US9077062B2 (en) | 2012-03-02 | 2015-07-07 | Lockheed Martin Corporation | System and method for providing an interchangeable dielectric filter within a waveguide |
US9544076B2 (en) * | 2012-05-04 | 2017-01-10 | Maxlinear, Inc. | Method and system for tunable upstream bandwidth utilizing an integrated multiplexing device |
CN105552495A (en) * | 2016-02-02 | 2016-05-04 | 李登峰 | Bottom-debugging cavity filter |
EP3660977B1 (en) | 2018-11-30 | 2023-12-13 | Nokia Solutions and Networks Oy | Resonator for radio frequency signals |
CN116995437A (en) * | 2023-09-26 | 2023-11-03 | 华南理工大学 | Gap waveguide antenna and vehicle millimeter wave radar |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2002082580A1 (en) * | 2001-04-03 | 2002-10-17 | South Bank University Enterprises Ltd | Tuneable dielectric resonator |
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US5083102A (en) * | 1988-05-26 | 1992-01-21 | University Of Maryland | Dual mode dielectric resonator filters without iris |
CA2217924C (en) * | 1997-12-12 | 2000-04-11 | Com Dev Limited | Collapsible pocket for changing the operating frequency of a microwave filter and a filter using the device |
ES2676093T3 (en) * | 2000-12-29 | 2018-07-16 | Alcatel Lucent | High performance microwave filter |
-
2004
- 2004-12-01 GB GBGB0426350.5A patent/GB0426350D0/en not_active Ceased
-
2005
- 2005-12-01 GB GB0712744A patent/GB2436493A/en not_active Withdrawn
- 2005-12-01 US US11/792,180 patent/US20080129422A1/en not_active Abandoned
- 2005-12-01 WO PCT/GB2005/050227 patent/WO2006059159A1/en active Application Filing
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2002082580A1 (en) * | 2001-04-03 | 2002-10-17 | South Bank University Enterprises Ltd | Tuneable dielectric resonator |
Non-Patent Citations (3)
Title |
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BUSLOV O Y ET AL: "Tuneable piezoelectric filter based on a dual-mode dielectric resonator", MICROWAVE AND TELECOMMUNICATION TECHNOLOGY, 2004. CRIMICO 2004. 2004 14TH INTERNATIONAL CRIMEAN CONFERENCE ON SEVASTOPOLL, CRIMEA, UKRAINE 13-17 SEPT. 2004, PISCATAWAY, NJ, USA,IEEE, US, 13 September 2004 (2004-09-13), pages 410 - 411, XP010797116, ISBN: 966-7968-69-3 * |
PETROV, P.K. ET AL.: "TUNEABLE TWO-POLE ONE-DIELECTRIC-RESONATOR FILTER WITH ELLIPTIC CHARACTERISTICS", INTEGRATED FERROELECTRICS, vol. 66, 2004, pages 261 - 266, XP008060759 * |
PETROV, P.K. ET. AL.: "TUNEABLE TWO-POLE ONE-DIELECTRIC-RESONATOR FILTER WITH ELLIPTIC CHARACTERISTICS", SIXTEENTH INTERNATIONAL SYMPOSIUM ON INTEGRATED FERROELECTRICS - GYEONGJU (KR), 5 April 2004 (2004-04-05) - 8 April 2004 (2004-04-08) * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2009000862A2 (en) * | 2007-06-26 | 2008-12-31 | Radiocomp Aps | Tuneable rf filters and methods thereof |
WO2009000862A3 (en) * | 2007-06-26 | 2009-03-26 | Radiocomp Aps | Tuneable rf filters and methods thereof |
Also Published As
Publication number | Publication date |
---|---|
GB0426350D0 (en) | 2005-01-05 |
US20080129422A1 (en) | 2008-06-05 |
GB0712744D0 (en) | 2007-08-08 |
GB2436493A (en) | 2007-09-26 |
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