GB2235339A - Microwave resonators and microwave filters incorporating microwave resonators - Google Patents
Microwave resonators and microwave filters incorporating microwave resonators Download PDFInfo
- Publication number
- GB2235339A GB2235339A GB8918636A GB8918636A GB2235339A GB 2235339 A GB2235339 A GB 2235339A GB 8918636 A GB8918636 A GB 8918636A GB 8918636 A GB8918636 A GB 8918636A GB 2235339 A GB2235339 A GB 2235339A
- Authority
- GB
- United Kingdom
- Prior art keywords
- resonator
- microwave
- block
- resonators
- ferrimagnetic material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P7/00—Resonators of the waveguide type
- H01P7/04—Coaxial resonators
-
- 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
- H01P1/215—Frequency-selective devices, e.g. filters using ferromagnetic material
- H01P1/217—Frequency-selective devices, e.g. filters using ferromagnetic material the ferromagnetic material acting as a tuning element in resonators
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Abstract
A magnetically tunable microwave resonator comprises a resonator block (11) made from a ferrimagnetic material. The effective permeability, and so the resonant frequency, of the resonator block can be altered by subjecting the block to a magnetic field bias which could be an external continuous magnetic field bias obtained from a coil 20, polo pieces (30, 31 Fig 3) or C-shaped ferrite cones (51, 51' Fig 5) or an internal, latched magnetic field bias obtained by a longitudinal or transverse current carrying wire (40, Fig 4). The inner and outer side surfaces of the block 11 are provided with metal layers 13, 14 eg silver, copper or aluminium. In a modification (Fig 6b) the resonator block may be of two axial sections (62, 63) one being of ferrimagnetic material and the other being of ceramic material. In a further arrangement two coaxial cylinders (60, 61, Fig 6a) may be used having the inner one of ferrimagnetic material and the other one of a high dielectric material. Magnetically tunable microwave filters are described (Fig 7a-7d) including a plurality of the magnetically tunable microwave resonators. <IMAGE>
Description
MICROWAVE RESONATORS AND MICROWAVE FILTERS INCORPORATING
MICROWAVE RESONATORS
This invention relates to microwave resonators and the invention also relates to microwave filters incorporating microwave resonators.
A known microwave resonator comprises a resonator block made from a high dielectric constant ceramic material.
The block has a square, or circular, transverse section and is formed with a longitudinal bore. Metal layers on the inner and outer side surfaces of the block are provided with suitable connectors which enable microwave power to be capacitively coupled to the resonator.
An important limitation of this known microwave resonator is that it has a fixed resonant frequency which is determined by the physical dimensions of the resonator block and by the dielectric constant of the ceramic material from which the block is made.
The present invention provides a magnetically tunable microwave resonator.
According to a first aspect of the present invention there is provided a magnetically tunable microwave resonator comprising a resonator block made, at least in part, from a ferrimagnetic material.
The ferrimagnetic material may be a microwave ferrite or garnet.
The resonant frequency of a microwave resonator as defined in accordance with the first aspect of the invention depends on the effective permeability, as well as the dielectric constant, of the ferrimagnetic material.
Accordingly, the resonant frequency of the resonator can be altered by changing the effective permeability of the ferrimagnetic material, and this can be accomplished by subjecting the block to a magnetic field.
Thus, the invention enables the microwave resonator to be tuned to a desired resonant frequency in a convenient, reliable and controllable manner.
In one embodiment, the microwave resonator includes electromagnetic means for subjecting the resonator block to an external continuous magnetic field bias, and the electromagnetic means may comprise a coil wound on the resonator block or an electromagnet having pole pieces disposed on opposite sides of the resonator block.
In an alternative embodiment, the resonator includes magnetizing means for subjecting the resonator block to an internal latched magnetic field bias, and the resonator block defines a closed magnetic circuit for the magnetic field produced by the magnetizing means.
The magnetizing means may comprise a current-supply wire extending through a longitudinal bore on the resonator block or through a transverse hole in the resonator block.
With this arrangement, the closed magnetic circuit retains the magnetization induced by the magnetic field even after an energizing current in the wire has been removed.
This enables the resonator block to be magnetized simply by supplying a current pulse to the wire, and thereby obviates the need for a continuous holding current and a bulky electromagnetic coil, and enables the resonant frequency to be changed rapidly.
The resonator block may be made entirely from a ferrimagnetic material or alternatively it may have a composite structure including both ferrimagnetic and ceramic materials.
According to a further aspect of the invention there is provided a magnetically tunable microwave filter including a plurality of magnetically tunable microwave resonators according to the first aspect of the invention.
Magnetically tunable microwave resonators and filters embodying the invention are now described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 shows a perspective view of a magnetically tunable microwave resonator;
Figures 2a and 2b illustrate the manner in which microwave power may be supplied to the microwave resonator of Figure 1;
Figure 3 illustrates one arrangement for subjecting the resonator to an external, continuous magnetic field bias;
Figures 4a and 4b respectively show longitudinal and transverse sectional views through a microwave resonator;
Figures 4c and 4d respectively show a longitudinal sectional view through, and a side elevational view of, another microwave resonator;
Figure 5 shows an arrangement for subjecting a microwave resonator to a latched magnetic field bias.
Figures 6a and 6b show microwave resonators having composite structures, and
Figures 7a to 7d show different microwave filter configurations.
Referring now to Figure 1, the magnetically tunable microwave resonator 10 comprises a resonator block 11 which is square in transverse section and has a longitudinal bore 12.
The block is made from a ferrimagnetic material, such as a magnetic ferrite or a magnetic garnet, and the inner and outer side surfaces thereof are provided with metal layers 13,14, typically of silver, copper or aluminium which may be applied to the surfaces by an electroplating technique or alternatively by a thick film printing technique. Lead wires are connected to metal layers 13,14 and enable microwave power to be capacitively coupled to the resonator.
As shown in Figure 2a, the inner layer 13 is connected to a first contact pad 15 on an electrically insulating support substrate 16, such as a printed circuit board, and the outer layer 14 is connected either to a second contact pad 17 or is placed in electrical contact with a conduction layer 18 disposed on the substrate. Alternatively, as shown in Figure 2b, the inner layer of the resonator could be connected to lead wires which extend through one or more transverse holes 19 formed in the resonator block to form a single pole filter.
The resonant frequency of this structure depends, in part, on the effective permeability of the ferrimagnetic material of the resonator block and, by changing the effective permeability of the block material, the resonant frequency of the resonator can be adjusted controllably.
In the embodiments shown in Figures 1 and 2, this object is achieved by subjecting the resonator block to an external, continuous magnetic field bias and, to that end, a coil 20, wound on the block, is supplied continuously with an electric current.
If the current supplied to the coil is increased, the resulting magnetic field increases in proportion causing a reduction in the effective permeability of the ferrimagnetic block material and a corresponding increase of the resonant frequency. Conversely, a decrease in the current supplied to the coil causes a corresponding decrease of the resonant frequency.
Since the electromagnetic field patterns produced in the resonator are of the TEM type, a reversal of the magnetic field direction has no effect on the resonator frequency.
Figure 3 shows an alternative arrangement for subjecting the resonator block 10 to an external, continuous magnetic field bias.
In this case, the resonator block is positioned between the pole pieces 30,31 of an electromagnet whose energizing coils 32 are supplied continuously with direct electric current of a magnitude corresponding to the desired resonant frequency.
To the extent that the embodiments described with reference to Figures 1 to 3 require a continuous holding current in order to maintain the desired resonant frequency, these arrangements may be inconvenient in some operational circumstances, especially if power-saving is a significant factor.
Moreover, the metal layer at the periphery of the resonator block has the effect of a shorted turn with the result that the centre frequency of the resonator changes relatively slowly as a function of the applied current.
Consequently, in some applications, it could be necessary to use a powerful (and so bulky) electromagnetic coil in order that the resonator may be capable of attaining a desired range of resonant frequencies.
The alternative embodiments, shown in Figures 4a to 4d, alleviate these short comings.
In these embodiments, the resonator block 10, again made of a ferrimagnetic material, is subjected to an internal, latched magnetic field bias.
The ferrimagnetic material of the resonator block is magnetized by means of a current-supply wire 40 which, in the examples shown, extends through the longitudinal bore 12 in the block (Figures 4a and b) or through a transverse hole 41 in the block (Figures 4c and d). In either case, the resonator block 10, which has the form generally of a toroid, defines a closed magnetic circuit for the magnetic field around the wire and thereby retains the magnetization induced by the magnetic field even after the energizing current in wire 40 has been removed. The magnetic field lines in the closed magnetic circuit are represented in Figures 4a and 4d by the broken lines F which encircle the wire.
The resonator block can be magnetized simply by supplying a current pulse to the wire, the resulting change in resonant frequency being proportional to the energy in the pulse, and this obviates the need for a continuous holding current and a bulky electromagnetic coil.
With an external latched magnetic field bias of this kind the resonator can be tuned to different resonant frequencies by varying the energy in the applied current pulse. This can be controlled using a suitable electronic driver circuit which enables a very fast operation, with typical switching times of the order of a microsecond.
If it is desired to reduce the level of magnetization to zero, this can easily be achieved by subjecting the resonator block to an alternating magnetic field.
Figure 5 shows an alternative embodiment for subjecting the resonator block 10 to a latched magnetic field bias. In this example, the resonator block is fitted with one or more electromagnets (50,50') each comprising a C-shaped ferrite core (51,51') carrying an energizing coil (52,52'). Each core, in combination with the resonator block, defines a closed magnetic circuit for the magnetic field generated by current pulses supplied to the energizing coils 52,52'. Again, the magnetization induced by the magnetic field is retained in the magnetic circuit even after the current pulses in the coils have been removed.
Clearly any number of electromagnets could be used.
The magnetization of most ferrimagnetic materials has a significant temperature dependency, and disappears at the Curie temperature of the material. This, of course, would affect the resonant frequency of the resonator.
In order to reduce the rate of change of magnetization with temperature it may be desirable to use compensated garnet materials or materials having high Curie temperatures, and the temperature dependency may be reduced still further by installing the resonator within a temperature-controlled oven, with the operating temperature set at a value slightly above the maxiumum operating temperature of the resonator. In this circumstance, it would be necessary to select a ferrimagnetic material with a saturated magnetization appropriate for the elevated operating temperature.
As shown in Figures 6a and 6b, the resonator block 10 need not necessarily be made entirely from ferrimagnetic material.
Thus, as shown in Figure 6a, the block, which is circular in transverse section, comprises two coaxial cylinders, 60,61, one (e.g. the inner cylinder 60) being made from a ferrimagnetic material and the other (e.g.
the outer cylinder 61) being made from a high dielectric constant ceramic material. Similarly, the resonator block shown in Figure 6b has two axial sections 62,63 one being made from a ferrimagnetic material and the other being made from a ceramic material.
Several magnetically tunable microwave resonators, in accordance with the invention, could be combined to form a magnetically tunable microwave filter.
Existing filter structures, as shown by way of example in Figures 7a to 7d, are embodied in ceramic materials.
In the present case, however, the microwave resonators, which constitute the filter structure, are embodied, at least in part, in a ferrimagnetic material, and any of the magnetic tuning techniques described hereinbefore may be used to adjust the resonant frequencies of the resonators thereby to tune the filter in a controllable manner.
The filter structure 70, shown in Figure 7a, comprises four microwave resonators 71, ... 74 arranged in side-by-side relationship on an electrically insulating substrate 75, such as a printed circuit board. Each resonator has a resonator block made from a ferrimagnetic material.
The inner metal layer of each resonator is connected, as shown, to a respective contact pad 76 on the substrate and the outer metal layers of the resonators all contact a common electrically conductive contact layer 77 on the substrate.
Microwave power enters and leaves the filter via respective coaxial connectors each being connected to layer 77 and to a respective end connector 78,79 associated with the contact pads 76. The resonant frequencies of the resonators can be adjusted by application thereto of a continuous or latched magnetic field bias, as described hereinbefore for a single resonator.
In Figures 7b and 7c, the microwave resonators are made from a monolithic block 80 of a ferrimagnetic material, the electromagnetic coupling between the individual resonators being adjusted by means of slots 81 in the block.
In Figure 7b, the coaxial connectors are shown at 82 and 83 and the associated end connectors are again referenced at 78 and 79.
It will be appreciated that a ferrimagnetic material may be used in place of the ceramic material used in many existing microwave filter configurations which combine several resonators, and any of the magnetic tuning methods described herein in relation to an individual resonator is equally applicable to a group of resonators constituting a microwave filter.
Figure 7d shows a yet further example of a filter structure comprising a coaxial arrangement of resonators.
As is known, several individually tunable filters may be combined together to provide a tunable duplexer or multiplexer or a tunable filter bank.
It will be appreciated that although the filters described with reference to Figure 7 operate in the TEM mode, the present invention is also applicable to filters operating in other electromagnetic modes.
In summary, the present invention provides microwave resonators and filters which are comprised, at least in part, of a ferrimagnetic material enabling them to be tuned magnetically in a convenient, reliable and controllable manner.
Claims (20)
1. A magnetically tunable microwave resonator comprising a resonator block made, at least in part, from a ferrimagnetic material.
2. A microwave resonator as claimed in claim 1 wherein the ferrimagnetic material is a microwave ferrite or a microwave garnet.
3. A microwave resonator as claimed in claim 1 wherein the resonator block has a longitudinal bore and has metal layers on the inner and outer side surfaces thereof.
4. A microwave resonator as claimed in any one of claims 1 to 3 including electromagnetic means for subjecting the resonator block to an external continuous magnetic field bias.
5. A microwave resonator as claimed in claim 4 wherein the electromagnetic means comprises a coil wound on the resonator block.
6. A microwave resonator as claimed in claim 4 wherein the electromagnetic means has pole pieces disposed to either side of the block.
7. A microwave resonator as claimed in any one of claims 1 to 3 including magnetizing means for subjecting the resonator block to an internal latched magnetic field bias and wherein the resonator block defines a closed magnetic circuit for the magnetic biassing field produced by the magnetizing means.
8. A microwave resonator as claimed in claim 7 wherein the magnetizing means includes a current-supply wire threading the resonator block.
9. A microwave resonator as claimed in claim 8 wherein the resonator block has a longitudinal bore and the wire extends through the bore.
10. A microwave resonator as claimed in claim 8 wherein the block has a longitudinal bore and the wire extends through a transverse hole in the block.
11. A microwave resonator as claimed in any one of claims 1 to 3 including electromagnetic means for subjecting the resonator block to an internal latched magnetic biassing field, wherein the electromagnetic means has a magnetic core which, in combination with the resonator block, defines a closed magnetic circuit for the magnetic biassing field.
12. A microwave resonator as claimed in any one of claims 1 to 11 wherein the resonator block is made entirely from ferrimagnetic material.
13. A microwave resonator as claimed in any one of claims 1 to 11 wherein the resonator block is made partly from a high dielectric constant ceramic material.
14. A microwave resonator as claimed in claim 13 wherein a first axial section of the resonator block is made from ferrimagnetic material and the remaining axial section is made from the high dielectric constant ceramic material.
15. A microwave resonator as claimed in claim 13 wherein an outer cylindrical part of the resonator block is made from one of the high dielectric constant ceramic material and the ferrimagnetic material and an inner cylindrical part of the resonator block is made from the other of these materials.
16. A magnetically tunable microwave filter including at least one magnetically tunable microwave resonators as claimed in any one of claims 1 to 15.
17. A microwave filter as claimed in claim 16 including a plurality of resonators which are formed, at least in part, from a monolithic block made from a ferrimagnetic material.
18. A microwave filter as claimed in claim 17, wherein the resonators are provided with slots and/or holes to modify the mutual electromagnetic coupling.
19. A magnetically tunable microwave resonator substantially as herein described with reference to the accompanying drawings.
20. A magnetically tunable microwave filter substantially as herein described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8918636A GB2235339B (en) | 1989-08-15 | 1989-08-15 | Microwave resonators and microwave filters incorporating microwave resonators |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8918636A GB2235339B (en) | 1989-08-15 | 1989-08-15 | Microwave resonators and microwave filters incorporating microwave resonators |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8918636D0 GB8918636D0 (en) | 1989-09-27 |
| GB2235339A true GB2235339A (en) | 1991-02-27 |
| GB2235339B GB2235339B (en) | 1994-02-09 |
Family
ID=10661677
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8918636A Expired - Fee Related GB2235339B (en) | 1989-08-15 | 1989-08-15 | Microwave resonators and microwave filters incorporating microwave resonators |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2235339B (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998020575A1 (en) * | 1996-10-25 | 1998-05-14 | Adc Solitra Oy | Resonator filter |
| US7687014B2 (en) * | 2008-03-26 | 2010-03-30 | Skyworks Solutions, Inc. | Co-firing of magnetic and dielectric materials for fabricating composite assemblies for circulators and isolators |
| CN102324601A (en) * | 2011-08-29 | 2012-01-18 | 摩比天线技术（深圳）有限公司 | Tunable filter |
| EP2886524A1 (en) * | 2013-12-18 | 2015-06-24 | Skyworks Solutions, Inc. | Tunable resonators using high dielectric constant ferrite rods |
| US11081770B2 (en) | 2017-09-08 | 2021-08-03 | Skyworks Solutions, Inc. | Low temperature co-fireable dielectric materials |
| US11387532B2 (en) | 2016-11-14 | 2022-07-12 | Skyworks Solutions, Inc. | Methods for integrated microstrip and substrate integrated waveguide circulators/isolators formed with co-fired magnetic-dielectric composites |
| US11565976B2 (en) | 2018-06-18 | 2023-01-31 | Skyworks Solutions, Inc. | Modified scheelite material for co-firing |
| US11603333B2 (en) | 2018-04-23 | 2023-03-14 | Skyworks Solutions, Inc. | Modified barium tungstate for co-firing |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| GB1173616A (en) * | 1965-12-30 | 1969-12-10 | Ibm | Microwave Absorption Device. |
| GB1356260A (en) * | 1970-11-05 | 1974-06-12 | Nat Res Dev | Tunable microwave filters |
| WO1983002853A1 (en) * | 1982-02-16 | 1983-08-18 | Motorola Inc | Ceramic bandpass filter |
| GB2132822A (en) * | 1982-12-06 | 1984-07-11 | Sony Corp | Ferromagnetic resonators |
| US4555683A (en) * | 1984-01-30 | 1985-11-26 | Eaton Corporation | Magnetically tunable resonators and tunable devices such as filters and resonant circuits for oscillators using magnetically tuned resonators |
| GB2163606A (en) * | 1984-08-21 | 1986-02-26 | Murata Manufacturing Co | Dielectric filter |
| GB2184608A (en) * | 1985-12-16 | 1987-06-24 | Murata Manufacturing Co | Mount for dielectric coaxial resonators |
| GB2194685A (en) * | 1986-07-02 | 1988-03-09 | Sony Corp | Ferromagnetic resonance devices |
| GB2197545A (en) * | 1986-09-29 | 1988-05-18 | Sony Corp | Ferromagnetic resonators |
-
1989
- 1989-08-15 GB GB8918636A patent/GB2235339B/en not_active Expired - Fee Related
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1173616A (en) * | 1965-12-30 | 1969-12-10 | Ibm | Microwave Absorption Device. |
| GB1356260A (en) * | 1970-11-05 | 1974-06-12 | Nat Res Dev | Tunable microwave filters |
| WO1983002853A1 (en) * | 1982-02-16 | 1983-08-18 | Motorola Inc | Ceramic bandpass filter |
| GB2132822A (en) * | 1982-12-06 | 1984-07-11 | Sony Corp | Ferromagnetic resonators |
| US4555683A (en) * | 1984-01-30 | 1985-11-26 | Eaton Corporation | Magnetically tunable resonators and tunable devices such as filters and resonant circuits for oscillators using magnetically tuned resonators |
| GB2163606A (en) * | 1984-08-21 | 1986-02-26 | Murata Manufacturing Co | Dielectric filter |
| GB2184608A (en) * | 1985-12-16 | 1987-06-24 | Murata Manufacturing Co | Mount for dielectric coaxial resonators |
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| GB2197545A (en) * | 1986-09-29 | 1988-05-18 | Sony Corp | Ferromagnetic resonators |
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998020575A1 (en) * | 1996-10-25 | 1998-05-14 | Adc Solitra Oy | Resonator filter |
| US6198364B1 (en) | 1996-10-25 | 2001-03-06 | Adc Telecommunications Oy | Resonator filter having a frequency regulating means with at least one turn |
| US7687014B2 (en) * | 2008-03-26 | 2010-03-30 | Skyworks Solutions, Inc. | Co-firing of magnetic and dielectric materials for fabricating composite assemblies for circulators and isolators |
| CN102324601A (en) * | 2011-08-29 | 2012-01-18 | 摩比天线技术（深圳）有限公司 | Tunable filter |
| US10559868B2 (en) | 2013-12-18 | 2020-02-11 | Skyworks Solutions, Inc. | Methods of forming tunable resonators using high dielectric constant ferrite rods |
| US10181632B2 (en) | 2013-12-18 | 2019-01-15 | Skyworks Solutions, Inc. | Tunable resonators using high dielectric constant ferrite rods |
| EP2886524A1 (en) * | 2013-12-18 | 2015-06-24 | Skyworks Solutions, Inc. | Tunable resonators using high dielectric constant ferrite rods |
| US11387532B2 (en) | 2016-11-14 | 2022-07-12 | Skyworks Solutions, Inc. | Methods for integrated microstrip and substrate integrated waveguide circulators/isolators formed with co-fired magnetic-dielectric composites |
| US11804642B2 (en) | 2016-11-14 | 2023-10-31 | Skyworks Solutions, Inc. | Integrated microstrip and substrate integrated waveguide circulators/isolators formed with co-fired magnetic-dielectric composites |
| US11081770B2 (en) | 2017-09-08 | 2021-08-03 | Skyworks Solutions, Inc. | Low temperature co-fireable dielectric materials |
| US11715869B2 (en) | 2017-09-08 | 2023-08-01 | Skyworks Solutions, Inc. | Low temperature co-fireable dielectric materials |
| US11603333B2 (en) | 2018-04-23 | 2023-03-14 | Skyworks Solutions, Inc. | Modified barium tungstate for co-firing |
| US11958778B2 (en) | 2018-04-23 | 2024-04-16 | Allumax Tti, Llc | Modified barium tungstate for co-firing |
| US11565976B2 (en) | 2018-06-18 | 2023-01-31 | Skyworks Solutions, Inc. | Modified scheelite material for co-firing |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8918636D0 (en) | 1989-09-27 |
| GB2235339B (en) | 1994-02-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19940509 |