Abstract
Aspects and embodiments relate to a cavity resonator assembly and filters formed from such cavity resonator assemblies. One aspect provides a resonator assembly comprising: a first resonator cavity, a first resonant member, and a first signal feed; a second resonator cavity, a second resonant member, and a second signal feed. The first resonant member is located within the first resonator cavity, arranged to receive a signal from the first signal feed and configured to resonate within the first cavity at a first fundamental frequency. The second resonant member is located within the second resonator cavity, arranged to receive a signal from the second signal feed and configured to resonate within the second cavity at a second fundamental frequency. At least a portion of the second cavity is housed within the first resonant member, and the first resonator cavity surface from which the first resonant member extends is offset from a second resonator cavity surface from which the second resonant member extends. Aspects and embodiments may provide resonator assemblies which offer a reduction in size compared to a typical dual band resonant structure. That is to say, arrangements may be such that limited additional physical space is required for a dual resonant structure compared to a single resonant structure. Aspects and embodiments may provide for increased flexibility and scalability when building filters from resonant structures compared to conventional filtering solutions.
Claims
1. A resonator assembly comprising: a first resonator cavity, a first resonant member, and a first signal feed; a second resonator cavity, a second resonant member, and a second signal feed; said first resonant member being located within said first resonator cavity, arranged to receive a signal from said first signal feed and configured to resonate within said first cavity at a first fundamental frequency; said second resonant member being located within said second resonator cavity, arranged to receive a signal from said second signal feed and configured to resonate within said second cavity at a second fundamental frequency; wherein said first and second fundamental frequencies are different and at least a portion of said second cavity is housed within said first resonant member, and wherein a first resonator cavity surface from which said first resonant member extends is offset from a second resonator cavity surface from which said second resonant member extends.
2. A resonator assembly according to claim 1, wherein said first and second cavities are configured to be substantially electrically and magnetically isolated from each other.
3. A resonator assembly according to claim 1, wherein said second resonator cavity comprises a cavity having a non-uniform cross-sectional area along its length.
4. A resonator assembly according to claim 3, wherein said second resonator cavity is configured in a general form of an inverted mushroom, a stem of said mushroom forming said first resonant member.
5. A resonator assembly according to claim 1, wherein at least one of said first and second resonator cavities comprises: a tunable screw extending into said resonator cavity.
6. A resonator assembly according to claim 5, wherein said second resonant member is formed from a tunable screw insert extending into said second resonator cavity.
7.-9. (canceled)
10. A resonator assembly according to claim 1, wherein configuring said first or second resonant member to resonate within said cavity at said first or second fundamental frequency respectively comprises: selecting at least one physical dimension of said resonant member.
11. A resonator assembly according to claim 1, wherein at least one of said first and said second resonant member comprises a resonating post.
12. A filter comprising: a plurality of resonator assemblies, at least one of said resonator assemblies comprising a resonator assembly according to claim 1, said filter comprising an input resonator assembly and an output resonator assembly arranged such that a signal received at said input resonator assembly passes through said plurality of resonator assemblies and is output at said output resonator assembly; an input feed line configured to transmit a signal to an input resonator member of said input resonator assembly such that said signal excites said input resonator member, said plurality of resonator assemblies being arranged such that said signal is transferred between said corresponding plurality of resonator members to an output resonator member of said output resonator assembly; an output feed line for receiving said signal from said output resonator member and outputting said signal.
13. A filter according to claim 12, comprising: at least two adjacent resonator assemblies, and wherein said adjacent resonator assemblies are configured such that a signal can be passed between adjacent first resonator cavities and a signal can be passed between adjacent second resonator cavities.
14. A filter according to claim 12, comprising at least two adjacent resonator assemblies, and wherein said adjacent resonator assemblies are configured such that a signal can be passed between adjacent first resonator cavities or a signal can be passed between adjacent second resonator cavities.
15. A filter according to claim 12, configured to form a filter of a duplexer.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:
[0029] FIG. 1 illustrates schematically, in side and plan view, layout of an existing dual-resonance coaxial cavity resonator; including quarter wavelength resonating elements;
[0030] FIG. 2 illustrates schematically, in side and plan view, a layout of a coaxial cavity resonator configured to support two resonances: fundamental resonant mode 1 and fundamental resonant mode 2;
[0031] FIG. 3 illustrates schematically, in side and plan view, an alternative layout of a coaxial cavity resonator configured to support two resonances: fundamental resonant mode 1 and fundamental resonant mode 2;
[0032] FIGS. 4a and 4b illustrate the distribution of electric field (magnitude) across a vertical plane of one possible resonator volume, for resonant, fundamental modes one and two respectively;
[0033] FIGS. 4c and 4d illustrate the distribution of magnetic field (magnitude) across a vertical plane of one possible resonator volume, for resonant, fundamental modes one and two respectively;
[0034] FIGS. 5a and 5b illustrate schematically, in side and plan view, layout configurations which allow for possible coupling between modes of a coaxial cavity resonator;
[0035] FIG. 5a shows capacitive coupling in which the layout includes an aperture to support coupling between the two modes;
[0036] FIG. 5b shows inductive coupling in which the layout includes a wire to support coupling between the two mode;
[0037] FIGS. 6a and 6b illustrate schematically, in side and plan view, layout configurations which allow for possible coupling between modes of a coaxial cavity resonator;
[0038] FIG. 6a shows capacitive coupling in which the layout includes a probe to support coupling between the two modes;
[0039] FIG. 6b shows inductive coupling in which the layout includes at least one aperture to support coupling between the two modes;
[0040] FIG. 7a illustrates the distribution of electric field (magnitude) across a vertical plane of one possible resonator volume;
[0041] FIG. 7b illustrates the distribution of magnetic field (magnitude) across a vertical plane of one possible resonator volume;
[0042] FIG. 8 illustrates schematically components of a possible resonant post which allows for post-fabrication tuning of one mode of a coaxial cavity filter;
[0043] FIGS. 9a to c illustrate schematically various assembly coupling arrangements in which resonator arrangements can be used to achieve increased efficiency in cross-couplings in the coaxial cavity filter technology; and
[0044] FIG. 10 illustrate schematically, in plan view, a layout of a coaxial cavity filter which achieves extended physical proximity as required to perform cross couplings.
DESCRIPTION OF THE EMBODIMENTS
[0045] Before discussing the embodiments in any more detail, first an overview will be provided.
[0046] FIG. 2 illustrates schematically one possible layout of a resonator assembly configured to support two resonances in accordance with one arrangement. As can be seen from the schematic side view and plan view shown in FIG. 2 of one possible arrangement, a resonator enclosure is provided. The resonator enclosure shown is configured such that within a cavity enclosure there is provided two cavities. A first cavity m1 is provided and supports operation of a first resonating element, m1, placed within a first cavity m1. There is also provided a second resonant mode supported by a second cavity m2 and associated resonating element, the m2 post, shown in FIG. 2. As can be seen in FIG. 2, within a space comparable to that of a traditional cavity enclosure, there exists two cavities: a cavity for supporting resonant mode 1 and a cavity for supporting resonant mode 2. In the arrangement shown, the outer shell of the cavity provided for resonant mode 1 forms the resonating element associated with resonant mode 2. The common wall is configured to play two roles within the enclosure; first, forming a cavity enclosure for the resonant mode 1 and, second, providing a resonant element for the resonant mode 2. In a configuration such as that shown schematically in FIG. 2, the isolation between the two modes/resonances is infinite since they are totally isolated by a magnetic wall. The shaded areas within FIG. 2 each schematically represent a cavity, one provided for each mode, m1 and m2.
[0047] As can be seen schematically in FIG. 2, arrangements may be such that two short-circuit planes are provided and two open-end regions are provided for each resonating member. That is to say, there are two ground planes, one for each mode supported within the overall resonant enclosure. One difference between the arrangement shown schematically in FIG. 2 and that of some known arrangements, for example, that of FIG. 1, is that the resonant member m1 has its own short circuit or ground plane. Provision of two separate ground planes allows for increased isolation between modes and, in the particular spatial physical arrangement shown in FIG. 2, there is provided an increased volume within which to store magnetic energy at resonance, thus allowing the m1 resonant mode to couple magnetically. Compared to known arrangements, an arrangement such as that shown schematically in FIG. 2 can allow for an improved physical configuration in relation to the coaxial resonating members in each cavity of the enclosure, that improved configuration allowing volume for magnetic energy storage and suppressing volume for electric energy storage, thus increasing in two ways the efficiency of the resonator and saving overall volume. An arrangement such as that shown schematically in FIG. 2 may also result in reduced complexity when achieving coupling between resonator enclosures and coupling between the two resonant cavities m1 and m2 when compared to the resonator enclosure shown in FIG. 2.
[0048] It will be appreciated that the high level of isolation between the two resonances in an arrangement such as that shown in FIG. 2 may allow for a minimum sacrifice in overall Q-factor. The physical configuration shown schematically in FIG. 2 can result in reduced design complexity in relation to filters formed from such enclosures. In particular, for example, in an arrangement such as that shown in FIG. 2, tuning of the two resonances may be effected substantially independently. Furthermore, post-fabrication tuning ability may significantly reduce overall design complexity, consequently leading to improved costs and time-to-market improvements and thereby improved overall efficiency. Further benefits may occur in relation to filters formed from a plurality of enclosures such as that shown in FIG. 2, since the physical arrangement of the cavities (if operating at the same fundamental frequency) shown in FIG. 2 may allow for planning and improved arrangement of physical components to allow for transmission zeros within a signal which can be of importance when implementing efficient signal filters.
[0049] FIG. 3 illustrates schematically an alternative arrangement of a coaxial cavity resonator assembly which is configured to support two resonances. The embodiment shown in FIG. 3 includes a resonating member in cavity m1 which extends downwardly from the inside of the resonating member provided in cavity m2. It will be appreciated that provision of appropriate tuning screws in relation to the resonating members positioned in each cavity may allow for tuning of the appropriate resonating cavity.
[0050] FIGS. 4a through to 4d illustrate schematically electric and magnetic field distributions within an arrangement such as that shown in FIG. 2. FIG. 4a and FIG. 4b show the distribution of the electric field (magnitude) on a vertical plane across the resonator volume for resonant fundamental modes m1 and m2 respectively. FIGS. 4c and 4d show the corresponding distribution of a magnetic field (magnitude) for modes m1 and m2 respectively. It can be seen from FIG. 4 that the structural configuration of an arrangement such as that shown in FIG. 2 is such that the resulting resonator assembly can support two resonant modes. The two modes, as they appear in FIG. 4, are electrically isolated. FIGS. 4c and 4d show the corresponding distribution of magnetic field (magnitude) in relation to modes m1 and m2 supported within the cavity. The lighter shades of grey represent a higher intensity.
[0051] Arrangements such as those shown schematically in FIGS. 2 and 3 can be implemented using current mass-market low cost fabrication techniques. Although the complexity of a resonator assembly and any resulting filter assemblies may be slightly increased compared to standard coaxial technology, some of the benefits offered by such an arrangement may compensate for such increased complexity. Post-fabrication tuning of assemblies and filters including resonator assemblies such as those shown schematically in FIGS. 2 and 3 is unlikely to add additional complexity to those devices.
[0052] A resonator assembly such as that shown schematically in FIG. 2 or FIG. 3 may be constructed to operate in various ways. In particular, it will be understood that the two resonant cavities may be configured such that they support different resonant frequencies or the same resonant frequency. In either case it is possible to feed the relevant cavities independently or simultaneously. Various modes of operation are described in more detail below.
Dual ResonanceFilters and Diplexers
[0053] According to some arrangements, a dual resonance coaxial cavity resonator is provided. Such a structure may be configured to support two modes at different frequencies or within different frequency bands: m1f1; m2f2. Some configuration can be used to support dual band filters and diplexers. In relation to, for example, the arrangements shown schematically in FIGS. 2 and 3, the two modes supported, m1f1 and m2f2, are supported in the isolated cavities m1 and m2 respectively. The two frequencies of the resonant cavities need not coincide and may be interchangeable. That is to say, f1 may be higher or lower in frequency than f2.
Dual ResonanceDuplexing
[0054] According to some configurations, a dual resonance coaxial cavity resonator is provided in a resonator enclosure such as that shown schematically in FIGS. 2 and 3. According to such a configuration, a structure is operable to support two modes of resonance at different frequencies, m1f1Tx1 and m2f2Rx1, where m1 stands for mode 1, f1 stands for frequency band 1 and Tx1 indicates the filter functionality in relation to a transmission mode. The structure of FIGS. 2 and 3 are particularly suited to such functionality due to the high level of isolation provided between the two resonant cavities. It will be understood that in relation to configurations such as those shown in FIGS. 2 and 3, the resonance at m1/m2 (m1f1, m2f2) may be such that the resonator enclosure can be used as a duplexing unit in a frequency division duplexing system. That is to say, one resonant cavity may be used for transmission and another for reception. It will further be understood that the previous configurations can be combined in order to provide a dual band duplexer.
Dual Mode
[0055] According to such a configuration, each of the two cavities m1, m2 provided in an arrangement such as that shown in FIGS. 2 and 3 may occur concurrently at the same frequency or within the same frequency band. According to such a configuration, it may be required that the two cavities provided within the enclosure, and the two fundamental resonances, are coupled. That is to say, cavities m1 and m2 are no longer independent and are, instead, coupled.
[0056] FIGS. 5 and 6 illustrate schematically various configurations according to which coupling between cavities m1 and m2 of a coaxial cavity resonator such as those shown in FIGS. 2 and 3 may be achieved.
[0057] FIG. 7 illustrates field distributions of such coupled modes.
[0058] FIG. 5a illustrates schematically one configuration according to which capacitive coupling may be achieved. In the arrangement shown in FIG. 5a, an aperture is included in the m2 post which supports coupling between the two modes m1f and m2f. According to the configuration shown in FIG. 5b, inductive coupling is used and the configuration of the cavities m1 and m2 are such that an inductive wire is provided. In such arrangements, m1f is the mode 1 frequency of resonance and m2f is the mode 2 frequency of resonance and, in the examples shown, they are the same frequency f.
[0059] FIG. 6a and FIG. 6b illustrate schematically possible configurations for achieving coupling between modes of a coaxial cavity resonating assembly such as that shown in FIGS. 2 and 3. FIG. 6a illustrates a configuration according to which capacitative coupling is provided between cavities m1 and m2. A probe is provided to support coupling between the two modes m1f and m2f. FIG. 6b illustrates schematically inductive coupling. The configuration shown in FIG. 6b illustrates an arrangement in which one or more apertures are used to achieve such inductive coupling. Again, in the arrangement shown, the resonant frequency in m1 is the same as the resonant frequency of cavity m2.
[0060] FIG. 7a illustrates, for a particular configuration of a two-pole coaxial cavity filter, the magnitude of the electric field within the cavities. FIG. 7b illustrates schematically for the same resonant assembly the dual-mode magnetic field magnitude.
Dual ModeTransmission Zeros
[0061] It has been recognised that when configured to operate in a dual mode, a resonator assembly such as that shown in FIG. 2 and FIG. 3 may be particularly suited to achieving transmission zeros in relation to cross couplings. FIG. 9 illustrates schematically coupling arrangements which allow increased flexibility in the way in which cross couplings can be achieved within a coaxial cavity filter arrangement comprising a plurality of resonator assemblies such as those shown in FIGS. 2 and 3.
[0062] FIG. 8 illustrates schematically one mechanism by which post-fabrication tuning within a resonator such as those shown in FIGS. 2 and 3 may be achieved. According to such an arrangement, a hollow resonating member in the form of a post is provided. That resonator post is fixed to the metallic cavity wall by solder being screwed in or pressed in. A tuning screw is provided which extends along the axis of the hollow resonator post. The tip of the tuning screw may extend beyond or through the end of the hollow resonator post. At the tip of the hollow resonator post or tuning screw, a high electric field with low current is achieved. Adjustment of the tuning screw within the hollow resonator post to project further from the hollow resonator post may allow for tuning of the resonating member within a resonant cavity. It will be appreciated that, tuning of a resonant assembly may be required post fabrication. Provision of tuning screws allows that post fabrication tuning to occur in an efficient manner. Use of tuning screws may relax manufacturing tolerance requirements.
[0063] FIG. 9 illustrates schematically various example coupling diagrams which demonstrate the flexibility and scalability of a resonator assembly such as that shown in FIGS. 2 and 3 if used in a manner where cavities m1 and m2 support the same resonant frequency. In particular, it will be appreciated that such coupling diagrams demonstrate that a resonator assembly such as that shown in FIGS. 2 and 3 may be used in filters formed from multiple such assemblies to achieve increased efficiency in cross couplings.
[0064] FIG. 9a shows a typical coupling diagram for a 4 pole filter. In this coupling diagram each pole, 1 to 4 can have coupling only between neighbouring poles. Physical representations are similar to an inline filter which prohibits physical proximity of non-neighbouring resonators. In real life coaxial cavity filters, the coupling diagram is changed from that of FIG. 9a to a folded coupling diagram. A physical representation of such a filter is one in which cavities are placed across from each other in a so-called folded configuration. In this way, physical proximity of non-adjacent cavities can be achieved. Such a folded configuration allows for the introduction of transmission zeros (TZs) in a filter response by implementing cross-couplings, which create several paths for a filtered signal. Such a folded configuration has limitations in relation to the number of nonadjacent resonators which can be arranged to be in physical proximity to allow for the required the cross-couplings.
[0065] FIG. 9b illustrates schematically an arrangement in which poles 2 and 3 of FIG. 9a with are replaced with a single pole: pole 2&3. This is possible since now poles 2&3 can take the physical form of a resonator enclosure such as that shown schematically in FIG. 2. This allows poles 1 and pole 4 to be brought into close proximity in a real physical configuration. The physical configuration of resonator assemblies is shown schematically in FIG. 10.
[0066] FIG. 9 shows alternative configurations which may be possible due to the configuration of a resonator enclosure such as the ones shown in FIGS. 2 and 3. FIG. 9 refers to configurations which employ one resonator enclosure such as that shown in FIG. 2, and shows the potential benefits of employing all or a number of the resonators in a filter to be of the form of the enclosure shown in FIG. 2.
[0067] Aspects and embodiments may provide for a reduction in size compared to a typical dual band resonant structure. That is to say, arrangements are such that limited additional physical space is required for a second resonant structure compared to a single resonant structure. Aspects and embodiments may provide for increased flexibility and scalability when building filters from resonant structures compared to conventional filtering solutions. Furthermore, aspects and embodiments may provide for improved out-of-band performance compared to conventional solutions.
[0068] A person of skill in the art would readily recognize that steps of various above-described methods can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods.
[0069] The functions of the various elements shown in the Figures, including any functional blocks labelled as processors or logic, may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term processor or controller or logic should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the Figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.
[0070] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.
[0071] The description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.
