Radio frequency resonators with bridge coupling adjacent resonators

Abstract

An iris bridge for coupling two radio frequency resonators includes: a body of dielectric material having an exposed first surface area, having a predetermined length, width and thickness, and having an elongate shape along the length of the body; a hole disposed through the body along the width of the body, the hole having a wall forming a second surface area of the body; and a conductive coating covering the exposed first surface area of the body and a first portion of the second surface area of the body. A second portion of the second surface area is free of conductive coating forming a non-conductive section of the wall of the hole. Such bridge may be tuned for coupling radio frequency resonators.

Claims

1. A bridge for coupling two radio frequency resonators, the bridge comprising: a body of dielectric material having an exposed first surface area, the body having an elongate shape and comprising an additional elongated part orthogonal to the elongate shape; a first hole disposed through the body, the first hole having a wall forming a second surface area of the body; an additional hole disposed through the additional elongated part, wherein the additional hole is orthogonal and symmetrical relative to the first hole; and a conductive coating covering the exposed first surface area of the body and a first portion of the second surface area of the body; wherein a second portion of the second surface area is free of conductive coating, so as to form a non-conductive section of the wall of the first hole.

2. The bridge according to claim 1, wherein the first hole is disposed through a central area of the body.

3. The bridge according to claim 1, wherein the first hole is disposed through an area offset from the center of the body.

4. The bridge according to of claim 1, wherein the first hole has a cylinder shape, and a diameter of the cylinder shape is smaller than a thickness of the body.

5. The bridge according to of claim 1, wherein the second portion of the second surface area covers at least 25% of the wall of the first hole.

6. The bridge according to claim 1, wherein the body of dielectric material has a predetermined length, a predetermined width, and a predetermined thickness; wherein the elongate shape is along the length of the body; and wherein the first hole is disposed through the body along the width of the body.

7. The bridge according to claim 1, wherein the non-conductive section of the wall of the first hole extends from an edge of the first hole into the first hole.

8. The bridge according to claim 7, wherein the first hole comprises a cylinder shape and a conical top, wherein the conical top is proximate to the edge of the first hole from which the non-conductive section of the wall of the first hole extends into the first hole.

9. A system, comprising: two radio frequency resonators, each comprising a monoblock of dielectric material having a predetermined shape and including surfaces areas; and a bridge for coupling the two radio frequency resonators, the bridge being positioned between the two radio frequency resonators and physically connected to opposing surface areas of the two radio frequency resonators; wherein the bridge comprises: a body of dielectric material having an exposed first surface area, an elongate shape, and an additional elongated part orthogonal to the elongate shape; a first hole disposed through the body, the first hole having a wall forming a second surface area of the body; an additional hole disposed through the additional elongated part; and a conductive coating covering the exposed first surface area of the body and a first portion of the second surface area of the body; wherein a second portion of the second surface area is free of conductive coating, so as to form a non-conductive section of the wall of the first hole; wherein the two radio frequency resonators are multimode radio frequency resonators; and wherein the bridge is configured to couple two orthogonal resonance modes of the two radio frequency resonators.

10. The system according to claim 9, wherein a length of the body of dielectric material of the bridge is smaller than or equal to a width of an adjacent surface layer of a radio frequency resonator of the two radio frequency resonators; and wherein the bridge is configured to couple a resonant frequency between the two radio frequency resonators.

11. The system according to claim 9, wherein the system is a multiple-input and multiple-output system.

12. The system according to claim 9, wherein the body of dielectric material has a predetermined length, a predetermined width, and a predetermined thickness; wherein the elongate shape is along the length of the body; and wherein the first hole is disposed through the body along the width of the body.

13. The system according to claim 9, wherein the monoblocks of the two radio frequency resonators comprise the same dielectric material as the body of the bridge.

14. The system according to claim 13, wherein the dielectric material is a ceramic material.

Description

SHORT DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a shows the electrical and magnetic vectors for two modes in two radio frequency resonators connected by a bridge.

(2) FIG. 1b shows the electrical and magnetic vectors for two modes in two radio frequency resonators of a different shape.

(3) FIG. 2a is a perspective view of two radio frequency resonators connected by a bridge with a cylindrical hole according to an embodiment.

(4) FIG. 2b is a side view of the bridge as shown on FIG. 2a.

(5) FIG. 3a is a perspective view of two radio frequency resonators connected by a bridge including a cylindrical hole with a conical top according to an embodiment.

(6) FIG. 3b is a side view of the bridge as shown on FIG. 3a.

(7) FIG. 4a is a perspective view of two radio frequency resonators connected by a bridge including a hole offset from the center according to an embodiment.

(8) FIG. 4b is a side view of the bridge as shown on FIG. 4a.

(9) FIG. 5a is a perspective view of two radio frequency resonators connected by a bridge including two orthogonal holes according to an embodiment.

(10) FIG. 5b is a side view of the bridge as shown on FIG. 5a.

(11) FIG. 6a is a perspective view of two radio frequency resonators connected by a bridge including multiple holes according to an embodiment.

(12) FIG. 6b provides side views of bridges similar to the bridge shown on FIG. 6a.

(13) FIG. 7 shows schematically a communication device in a wireless communication system.

DETAILED DESCRIPTION

(14) Below a description of embodiments will follow. In the following description of embodiments of the disclosure, the same reference numerals will be used for the same or equivalent features in the different drawings.

(15) The embodiments described below relate to bridges for coupling radio frequency resonators that comprise a solid body of dielectric material. The body may be shaped as an elongate parallelepiped or as any other elongate shape that allows for coupling of two modes of adjacent resonators.

(16) FIGS. 1a and 1b are simple illustrations of parallel resonant modes appearing in adjacent radio frequency resonators.

(17) The magnetic and electric field configurations of parallel modes in adjacent radio frequency resonators 101 can be seen in FIGS. 1a and 1b. By coupling energy across two or more resonators 101 in a similar fashion, it is possible to use them to form a filter.

(18) The magnetic fields H1, H2 indicated by field vectors 111 correspond to the electric fields E1 and E2 indicated by field vectors 110. As it is clear to a skilled person, since the magnetic field lines 111 follow the electric field lines 110, there are regions between the resonators 101 where the magnetic fields are parallel to each other. For example, H1 is substantially parallel to H2 near the adjacent edges of resonators 101. By placing an elongated iris bridge 100 between either the short or long wall of two adjacent resonator blocks, two parallel modes can be magnetically coupled together, for example H1 and H2 in FIGS. 1a and 1b.

(19) In order for a bridge 100 positioned like this to provide a cheap, simple and effective means of accurately controlling and varying the coupling of the magnetic fields through it, while keeping the effect of variations in mechanical dimensions on the resultant electrical performance minimal, the bridge 100 includes additional features described in further detail in the embodiments below. The effect on resultant electrical performance is minimized to reduce sensitivity dimensional variations that result e.g. from an imprecise manufacturing process.

(20) FIGS. 2a-2b, 3a-3b, 4a-4b and 5a-5b are all paired such that the first figure shows the bridge 100 implemented between adjacent resonators, and the second figure in the pair shows the embodiment outside of the structure.

(21) For the purposes of this description, examples shown in the Figures are limited to dual-mode resonators of symmetrical parallelepiped shape, for clarity and consistency. As would be clear to a skilled person, all aspects of the disclosure are applicable without limitation to resonators of any other shape suitable for single-mode, dual-mode or multimode resonance.

(22) FIG. 2a shows a bridge 100 disposed between two radio frequency resonators, forming the structure 101. FIG. 2b provides a zoomed-in side view 200 of the bridge 100. The bridge 100 comprises a body of dielectric material having an exposed surface area and a predetermined length L, width W and thickness T, indicated in FIGS. 2a-2b. The body of the bridge has an elongate shape along its length L. The shape may be a parallelepiped as shown in the Figures for clarity only, or any other suitable elongate shape. The bridge 100 further comprises a hole 202 disposed through the body along its width W. The hole 202 has a wall inside of it, forming a second surface area 222 of the body. The second surface area 222 has a first portion that is covered with a conductive coating, along with the exposed surface area of the body. The second surface area 222 also comprises a second portion 112 free of conductive coating. The conductive coating can be formed of a highly conductive material, for example metal.

(23) The width W of the body of the bridge is chosen so as to be mechanically feasible to produce with the chosen manufacturing technique, but small enough to also result in minimal coupling between other resonant modes, for example the two modes that are orthogonal to the direction of the length of the bridge.

(24) In the embodiment of FIGS. 2a-2b, a single cylindrical through hole 202 is disposed in the center of the bridge 100, with a diameter that is smaller than the thickness T of the bridge, and defined by the spacing between the two resonator blocks. The inner wall of the hole is completely covered in conductive coating, and provides a boundary condition for fields in both cavities in this completely coated form.

(25) After manufacture, nominal coupling between the two modes is determined by a gap in the material between the through hole 202 and the edge of the bridge 100 along the thickness of the bridge 100. For many applications below 6 GHz and at bandwidths that can be considered narrow, the coupling will be minimal or zero. In order for the coupling to operate, a small amount of conductive coating is removed from the top section 112 of the conductively-coated inner surface 222 of the hole 202, forming a non-conductive post 122 as shown in FIG. 2b. The existing boundary condition of the post 122 changes as the conductive coating is removed, with the post 122 becoming an open-circuit stub, resonant at a frequency much higher than either of the frequencies of the modes to be coupled. Coupling between the two modes occurs with this stub acting as a bypass that serves to strengthen the coupling significantly. The coupling may initially be so much stronger than the coupling in a bridge 100 without a post 122, that it in some cases it may become unusable. Further removal of conductive coating causes the amount of coupling between the two modes to reduce. After approximately 25% of the inner wall 222 of the hole being non-conductive, the relation between height of the post 122 and the coupling bandwidth can become linear and reduce towards the nominal coupling of an equally sized bridge without a post as height of the post 122 tends towards zero. Accordingly, in an embodiment 25% or more of the wall 222 of the hole 202 is non-conductive, which allows for more precise and predictable control of the coupling between the resonators.

(26) As the conductive coating that forms the top part of the post is also part of an external ground, the interior of the bridge 100 may become exposed to the air/environment. As all magnetic field vectors are perpendicular to the axis of the post where this hole is, minimal radiation (and therefore loss) will occur provided that the hole is small. For many sub-6 GHz applications, this hole diameter will typically be less than 2 mm. The lower limit of the hole diameter is determined by the manufacturing process.

(27) FIGS. 3a and 3b illustrate an embodiment, wherein instead of a plain cylindrical hole in the iris bridge 100, a part of the hole 302 is formed as a cone 322. Similarly, part of the conductive coating on the inner wall of the hole 302 is removed. The cone 322 also presents a surface area 312 in the plane of the bridge length accessible to a tool that could further remove conductive coating in order to adjust the coupling. The tool could be a mechanical grinding tool, a laser ablation tool, or any other tool.

(28) A cylindrical hole 202 can be easier to manufacture, while a hole 302 with a conical part 322 can provide better access for partial removal of conductive coating from its surface area. Conductive coating can be selectively removed in circles from the top of the conical section 312, similar to the cylindrical section in the embodiment of FIGS. 2a-2b. The coupling can initially be very large and decrease non-linearly, as previously, but eventually will tend towards a region of approximately linear tuning.

(29) The angle of the conical surface of the hole 302 can be chosen based on the resolution of tuning required and the capability of the tuning tool, i.e. the smallest amount of material that can be removed in one circular path. When the accuracy of the tool is lower, a more shallow angle and greater upper cone diameter is used. This results in a reduced tuning range. The exact dimensions required will be unique to each design and should be optimized accordingly based on filter specifications, manufacturing process and available tuning tools.

(30) FIGS. 4a and 4b illustrate an embodiment wherein the hole 402 in the body of the bridge 100 is offset from the center of the body. The hole 402 illustrated herein is a hole with a conical part like the hole 302 of FIGS. 3a-3b. However, as is clear to a skilled person, the hole may have any other shape.

(31) FIG. 4b illustrates the offset (df) of the hole 402 along the x-axis coinciding with length. In an extension of this embodiment, the bridge 100 itself may also be offset (di), in addition to the offset (df). These two offsets (df, di) can be arbitrarily and independently set in any direction along the x-axis.

(32) By offsetting the hole 402 its efficacy in adjusting coupling is reduced the closer it is to the iris bridge 100 wall. A reduced sensitivity may be desirable with a larger bridge 100 or for other design considerations.

(33) FIGS. 5a and 5b show an embodiment wherein the bridge 500 is of an elongate shape in two orthogonal directions. Each orthogonal leg of the bridge is arranged to independently provide coupling between two adjacent vertical modes and two adjacent horizontal modes, respectively. In this embodiment the adjacent radio frequency resonators are dual-mode or multimode resonators.

(34) Holes 502 are disposed in the orthogonal legs of the body of the bridge 500 to provide the tuning. In this example, a combination of through cylindrical holes combined with cones is used, however any combination of similar or different holes may be used for the same effect.

(35) Owing to the central section of the iris bridge 500 being occupied by the material that forms the orthogonal structure, both holes 502 are offset from the center, as shown more clearly in FIG. 5b. Undesired harmonic couplings may also restrict the offsets of the holes 502. Removing sections of conducting coating from the top 512 of each of the holes 502, as in previous embodiments, allows for precise, selective and independent control of both horizontal and vertical coupling bandwidths, through horizontal and vertical legs of the iris bridge 500, respectively.

(36) FIG. 6a shows a system 101 with a bridge 100 that comprises multiple parallel holes 602. FIG. 6b shows various examples of three parallel holes 602, 602′, 602″. In other examples, any number of holes may be disposed through the body of the bridge 100. An odd number may be preferred because an odd number of holes includes a central hole which allows for optimal control.

(37) The disclosure in this embodiment can operate in various ways. The first one shown in the rightmost schematic of FIG. 6b, and shows one outermost through hole that has no conductive coating removed (un-tuned), and the other outermost through-hole having approximately 50% of the conductive coating removed from its inner wall, tuned to an initial fixed height of the post. This left post operates as an auxiliary tuner and sets a basic nominal tuning range for the bridge 100. A third, central post can then be tuned progressively until the desired coupling bandwidth is obtained.

(38) This embodiment is especially suitable for small bandwidths and/or filters where multiple bandwidth variations may be required from the same physical part. It is also suitable when a manufacturing process that has significant physical variations and/or poor tolerances is used.

(39) A second configuration of this embodiment is shown in the central and leftmost schematic of FIG. 6b. In these schematics, both outermost posts operate as auxiliary tuners and are tuned equally and symmetrically to set the nominal coupling value provided by the iris bridge 100. The center, main tuning feature, is then used to fine-tune the coupling bandwidth to the desired value.

(40) This configuration is also useful where a greater range of tuning is required—either to enable the tuning of multiple filter bandwidths from a single common filter part or to enable the use of processes with poor tolerances. It will also have the effect of controlling the propagation of a third harmonic resonance, which may be useful in certain cases.

(41) Both asymmetric and symmetric auxiliary hole configurations described above can be scaled to use any number of tuning holes, not limited by type, design or order. The selection and combination of features used will depend on design requirements and any associated constraints of a given design.

(42) FIG. 7 shows schematically a communication device 300 in a wireless communication system 400. The communication device 300 comprises a system 700 of two or more radio frequency resonators coupled through a bridge according to any of the embodiments of the disclosure. The wireless communication system 400 also comprises a base station 500, which may also comprise a system 700 of two or more radio frequency resonators coupled by the bridges according to any one of the embodiments described above. The dotted arrow Al represents transmissions from the communication device 300 to the base station 500, which are usually called up-link transmissions. The full arrow A2 represents transmissions from the base station 500 to the communication device 300, which are usually called down-link transmissions.

(43) The communication device 300 may be any of a user equipment (UE) in Long Term Evolution (LTE), mobile station (MS), wireless terminal or mobile terminal which is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UE may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice or data, via the radio access network, with another entity, such as another receiver or a server. The UE can be a station (STA), which is any device that contains an IEEE 802.11-conformant media access control (MAC) and physical layer (PHY) interface to the wireless medium (WM).

(44) The communication device 300 may also be a base station, a (radio) network node, an access node or an access point, e.g., a Radio Base Station (RBS), which in some networks may be referred to as transmitter, “eNB”, “eNodeB”, “NodeB” or “B node”, depending on the technology and terminology used. The radio network nodes may be of different classes such as, e.g., macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network node can be a station (STA), which is any device that contains an IEEE 802.11-conformant media access control (MAC) and physical layer (PHY) interface to the wireless medium (WM).

(45) Embodiments of the application are compatible at least with three-axis machining and high-volume, molded manufacturing methods such as, but not limited to, single axis isostatic-pressing, die-pressing, vacuum forming, super-plastic forming, injection-molding, 3D printing, etc. The conductive material removal from any of the elements described in the embodiments above may be performed by laser ablation, mechanical grinding or any other suitable technique.