EP3375037A1

EP3375037A1 - Radio frequency signal combiner

Info

Publication number: EP3375037A1
Application number: EP15804787.8A
Authority: EP
Inventors: Vlad Lenive
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2015-12-04
Filing date: 2015-12-04
Publication date: 2018-09-19
Also published as: CN108370079A; WO2017092820A1; CN108370079B

Abstract

A radio frequency (RF) signal power combiner includes an axially symmetric periodic waveguide device with a cylinder and a central conductor disposed coaxially within the cylinder. The central conductor is defined by a pair of orthogonal symmetry planes. A shorting wall closes an end of the cylinder and is electrically coupled to the central conductor. Magnetic loop coupling elements are disposed within the cylinder relative to a first symmetry plane of the pair of orthogonal symmetry planes. A plurality of input ports extend through respective openings in the shorting wall, each feeding a signal to a corresponding magnetic loop coupling element. An output port configured to output a combined power of signals from the plurality of input ports is disposed on a side of the combiner away from the shorting wall.

Description

RADIO FREQUENCY SIGNAL COMBINER

TECHNICAL FIELD

[0001] The aspects of the present disclosure relate generally to power combiners and in particular to a RF signal power combiner for an antenna array. BACKGROUND

[0002] Wireless communication systems in densely populated areas face the problem of intense utilization of the available radio frequency (RF) radio spectrum. The economic efficiency of the mobile network operators leads to increases in the level of RF power required for a bit rate throughput within the limitations of energy efficiency and cost.

[0003] Achieving substantially high levels of RF power in an antenna array is a technical challenge leading to a number of problems. For example, the number of inputs of the combiner is generally limited by the amount of coupling achievable for each input, which in turn is limited by the electromagnetic properties of the combiner. An example of this is a planar (printed) combiner that is based on magnetic coupling between two primary and single secondary windings of the RF transformer. As the number of primary coils (i.e. the number of inputs) increases, the area and/or number of turns of the secondary coil has to increase. This in turn affects the self-resonance frequency of the combiner, providing a natural limit to the number of primary coils. The hardware realization often limits the number of inputs to two. Having a considerable number of inputs in a combiner therefore requires cascading several 2x1 combiners into a larger network, leading to considerable insertion loss. [0004] Hybrid waves have extensive application in antenna technology. The only known combiner employing hybrid waves is based on electric coupling to the lowest dominant hybrid wave. The main technical issue in this case is that there is an insufficient amount of coupling physically achievable with the electric probe, and the difficulties in placing more than one pair of electric probes in the maximum field of the hybrid wave. This leads to excessively long coupling probes occupying more than one period of the axially symmetric periodic waveguide or quasiperiodic structures (ASPS), with consequently excessive outline dimensions of the combiner. A limitation of electric probes is that they need to have source signals in counter phase.

[0005] Accordingly, it would be desirable to provide an RF signal power combiner that addresses at least some of the problems identified above.

SUMMARY

[0006] It is an object of the present invention to provide an improved radio frequency signal power combiner. This object is solved by the subject matter of the independent claims. Further advantageous modifications can be found in the dependent claims.

[0007] According to a first aspect of the present invention, the above and further objects and advantages are obtained by a radio frequency (RF) signal power combiner. The combiner includes an axially symmetric periodic waveguide device. The axially symmetric periodic waveguide device includes a cylinder, with a central conductor disposed coaxially within the cylinder. The central conductor is defined by a pair of orthogonal symmetry planes. A shorting wall closes an end of the cylinder and electrically couples the cylinder and the central conductor. At least one pair of magnetic loop coupling elements is disposed within the cylinder relative to a first symmetry plane of the pair of orthogonal symmetry planes defining the central conductor. A plurality of input ports extend through respective openings in the shorting wall, a respective one of the plurality of input ports feeding a signal to a corresponding one of the at least one pair of magnetic loop coupling elements. An output port is disposed on a side of the combiner away from the shorting wall, the output port configured to output a combined power of signals from the plurality of input ports. The aspects of the disclosed embodiments enable substantially high levels of RF power to be achieved in an antenna array using several relatively low power sources.

[0008] In a first possible implementation form of the radio frequency signal combiner according to the first aspect, the cylinder comprises (or is) a conductive cylinder and the at least one pair of magnetic loop coupling elements is supported on a dielectric card. The use of magnetic loop coupling elements enables a greater amount of coupling than is physically achievable with the electric probe and allows the closed loop to be located entirely within the volume of its corresponding compartment.

[0009] In a second possible implementation form of the radio frequency signal combiner according to the first possible implementation form, the shorting wall electrically couples the central conductor and the conductive cylinder. The electrical coupling can include a mechanical connection, a galvanic coupling or a capacitive coupling. The use of the shorting wall to electrically couple the shorting wall and conductive cylinder can provide more compact outline dimensions and ease in manufacturing.

[0010] In a third possible implementation form of the radio frequency signal combiner according to the first and second possible implementation forms, the at least one pair of magnetic loop coupling elements is printed on a first side of the dielectric card. The use of magnetic loop coupling elements enables a greater amount of coupling than is physically achievable with the electric probe and allows the closed loop to be located entirely within the volume of its corresponding compartment.

[0011] In a fourth possible implementation form of the radio frequency signal combiner according to the first through third possible implementation forms a pair of the at least one pair of magnetic loop coupling elements are disposed co-planar with each other and with the first symmetry plane. The presence of electric and magnetic walls allows for positioning of the magnetic coupling elements symmetrical to those surfaces to achieve maximum possible coupling without breaking the intended field distribution.

[0012] In a fifth possible implementation form of the radio frequency signal combiner according to any one of the first through fourth possible implementation forms a first magnetic loop element of the co-planar pair of magnetic loop coupling elements is disposed equidistant from a second magnetic loop coupling element of the co-planar pair of magnetic loop coupling elements relative to the central conductor. The coupling elements are positioned symmetrical to the electric and magnetic walls to achieve maximum possible coupling without breaking the intended field distribution.

[0013] In a sixth possible implementation form of the radio frequency signal combiner according to any of the first through fifth possible implementation forms, the radio frequency signal combiner includes a conductive track on a second side of the dielectric cards, the conductive track being coupled to the respective one of the plurality of input ports. This allows the input signal to be coupled to the magnetic coupling loop.

[0014] In a seventh implementation form of the radio frequency signal combiner according to any of the first through sixth possible implementation forms the magnetic loop coupling elements are galvanically coupled to the conductive track. This allows the signals from the input ports to be fed to the coupling loops.

[0015] In an eighth possible implementation from of the radio frequency signal combiner according to any of the first through seventh implementation forms the dielectric cards are disposed in dielectric card receiving slots of the central conductor. The central conductor is able to support the dielectric cards within the combiner in any number of positions and enables an increased number of input ports.

[0016] In a ninth possible implementation form of the radio frequency signal combiner according to the first aspect as such, or any of the preceding implementation forms, the magnetic loop coupling elements of the at least one pair of magnetic loop coupling elements comprise figure-of-eight magnetic loop coupling elements. This topology generates a magnetic flux of equal strength but of an opposite direction. The loop has the forward and return directions of the magnetic flux, providing the most efficient coupling.

[0017] In a tenth possible implementation form of the radio frequency signal combiner according to the first aspect as such, or any of the preceding implementation forms, at least a first symmetry plane of the pair of orthogonal symmetry planes defining the central conductor crosses all magnetic loop coupling elements of the at least one pair of magnetic loop coupling elements. This allows the internal volume of the ASPS to be compartmentalized into two cells separated by a magnetic wall and enable magnetic loop coupling to the magnetic field inside the cell.

[0018] In an eleventh possible implementation form of the radio frequency signal combiner according to the first aspect as such, the cylinder comprises (or is) a dielectric cylinder and the magnetic loop coupling elements of the at least one pair of magnetic loop coupling elements are arranged and preferably printed on a surface of the dielectric cylinder. The mechanical assembly of the combiner is simplified and allows for an increased number of input ports with an associated reduction in mechanical components.

[0019] In a twelfth possible implementation form of the radio frequency signal combiner according to the eleventh possible implementation form, the radio frequency signal combiner includes a conductive cylinder. The central conductor and the dielectric cylinder are disposed co-axially within the conductive cylinder. The shorting wall electrically couples the central conductor and the conductive cylinder. The electrical coupling can include a mechanical connection, a galvanic coupling or a capacitive coupling. The use of a dielectric cylinder can provide enhanced interport isolation and power handling.

[0020] In thirteenth possible implementation form of the radio frequency signal combiner according to the twelfth possible implementation form, the radio frequency signal combiner includes conductive tracks arranged and preferably printed on an inner surface of the dielectric cylinder, the conductive tracks being coupled to the respective one of the plurality of input ports for feeding the signal to the corresponding one of the at least one pair of magnetic loop coupling elements. The mechanical assembly of the combiner is simplified and allows for an increased number of input ports with an associated reduction in mechanical components.

[0021] In a thirteenth possible implementation form of radio frequency signal combiner of the eleventh and twelfth possible implementation forms, the magnetic loop coupling elements of the at least one pair of magnetic loop coupling elements are disposed equidistant from each other relative to the central conductor. The coupling elements are positioned symmetrical to the electric and magnetic walls to achieve maximum possible coupling without breaking the intended field distribution.

[0022] In a fourteenth possible implementation form of the radio frequency combiner according to the first aspect as such or of any of the preceding implementation forms, the axially symmetric periodic waveguide device supports a hybrid wave signal. The power combiner of the disclosed embodiments exploits the natural properties of the hybrid, azimuthally non-uniform wave.

[0023] In a fifteenth possible implementation form of the radio frequency combiner according to the first aspect as such or of any of the preceding implementation forms, an internal volume of the axially symmetrical periodic waveguide device is divided by the pair of orthogonal symmetry planes into at least one pair of compartments, wherein a compartment of the at least one pair of compartments has a dedicated magnetic loop coupling element and an input port. When the coupling elements feed with correct amplitudes and phases, a combination of energy occurs, providing the power combining effect.

[0024] In a sixteenth possible implementation form of the radio frequency combiner according to the first aspect as such or of any of the preceding implementation forms, the axially symmetric periodic hybrid waveguide device is a disk-on-rod antenna assembly. The disk-on-rod antenna assembly belongs to the class of guiding structures supporting hybrid modes. An advantage of this class of guiding structures is the possibility to support HEmn hybrid waves having not only one, but two cut-off frequencies, a low cut-off frequency and a high cut-off frequency.

[0025] According to a second aspect of the present invention, the above and further objects and advantages are obtained by a radio frequency (RF) signal power combiner. The combiner includes an axially symmetric periodic waveguide device. The axially symmetric periodic waveguide device includes a dielectric cylinder, with a central conductor disposed coaxially within the dielectric cylinder. The central conductor is defined by a pair of orthogonal symmetry planes. A shorting wall closes an end of the dielectric cylinder and is electrically coupled to the central conductor. At least one pair of magnetic loop coupling elements is disposed on a surface of the dielectric cylinder relative to a first symmetry plane of the pair of orthogonal symmetry planes defining the central conductor. A plurality of input ports extend through respective openings in the shorting wall, a respective one of the plurality of input ports feeding a signal to a corresponding one of the at least one pair of magnetic loop coupling elements. An output port is disposed on a side of the combiner away from the shorting wall, the output port configured to output a combined power of signals from the plurality of input ports. The aspects of the disclosed embodiments enable substantially high levels of RF power to be achieved in an antenna array using several relatively low power sources.

[0026] According to a third aspect of the present invention, the above and further objects and advantages are obtained by a radio frequency (RF) signal combiner. The combiner includes an external conductive cylinder, a dielectric cylinder with a central conductor disposed coaxially within the dielectric cylinder, the dielectric cylinder being disposed coaxially within the external conductive cylinder. The central conductor is defined by a pair of orthogonal symmetry planes. A shorting wall closes an end of the dielectric cylinder and the external conductive cylinder and is electrically coupled to the central conductor and the external conductive cylinder. The electrical coupling can include one or more of a mechanical connection, a galvanic coupling or a capacitive coupling. At least one pair of magnetic loop coupling elements is disposed on a surface of the dielectric cylinder. A plurality of input ports extend through respective openings in the shorting wall, and conductive tracks are arranged and preferably printed on an outer and inner surface of the dielectric cylinder and connected using dedicated vias. The aspects of the disclosed embodiments enable substantially high levels of RF power to be achieved in an antenna array using several relatively low power sources.

[0027] According to a fourth aspect of the present invention, the above and further objects and advantages are obtained by a radio frequency (RF) signal power combiner. The combiner includes an axially symmetric periodic waveguide device. The axially symmetric periodic waveguide device includes a conductive cylinder, a central conductor disposed coaxially within the conductive cylinder, the central conductor defined by a pair of orthogonal symmetry planes. A shorting wall closes an end of the conductive cylinder and electrically couples the central conductor to the conductive cylinder. The electrical coupling can include a mechanical connection, a galvanic coupling or a capacitive coupling. A dielectric support member supports the central conductor within the conductive. At least one pair of magnetic loop coupling elements is disposed within the conductive cylinder relative to a first symmetry plane of the pair of orthogonal symmetry planes defining the central conductor. A dielectric member supports the at least one pair of magnetic loop coupling elements and an end of the central conductor adjacent the shorting wall. The dielectric member is disposed between the shorting wall and the central conductor. A plurality of input ports extend through respective openings in the shorting wall, a respective one of the plurality of input ports feeding a signal to a corresponding one of the at least one pair of magnetic loop coupling elements. An output port is disposed on a side of the combiner away from the shorting wall, the output port configured to output a combined power of signals from the plurality of input ports. The aspects of the disclosed embodiments enable substantially high levels of RF power to be achieved in an antenna array using several relatively low power sources.

[0028] In a first possible implementation of the fourth aspect as such, the dielectric support member surrounds the central conductor within the conductive cylinder.

[0029] In a second possible implementation of the fourth aspect as such or the first possible implementation form, the dielectric support member is dielectric foam.

[0030] In a third possible implementation of the fourth aspect as such, or any of the preceding possible implementation forms, the dielectric support member electrically isolates the central conductor from the conductive cylinder and the shorting wall.

[0031] According to a fifth aspect of the present invention, the above and further objects and advantages are obtained by a radio frequency (RF) signal power combiner. The combiner includes an axially symmetric periodic waveguide device. The axially symmetric periodic waveguide device includes a dielectric cylinder, a central conductor disposed coaxially within the dielectric cylinder, the central conductor defined by a pair of orthogonal symmetry planes. A shorting wall closes an end of the dielectric cylinder and is electrically coupled to the central conductor. The electrical coupling can include a mechanical connection, a galvanic coupling or a capacitive coupling. A dielectric support member supports the central conductor within the dielectric cylinder. At least one pair of magnetic loop coupling elements is disposed on a surface of the dielectric cylinder relative to a first symmetry plane of the pair of orthogonal symmetry planes defining the central conductor. A dielectric member can support the end of the central conductor adjacent the shorting wall. The dielectric member is disposed between the shorting wall and the central conductor. A plurality of input ports extend through respective openings in the shorting wall, a respective one of the plurality of input ports feeding a signal to a corresponding one of the at least one pair of magnetic loop coupling elements. An output port is disposed on a side of the combiner away from the shorting wall, the output port configured to output a combined power of signals from the plurality of input ports. The aspects of the disclosed embodiments enable substantially high levels of RF power to be achieved in an antenna array using several relatively low power sources.

[0032] These and other aspects, implementation forms, and advantages of the exemplary embodiments will become apparent from the embodiments described herein considered in conjunction with the accompanying drawings. It is to be understood, however, that the description and drawings are designed solely for purposes of illustration and not as a definition of the limits of the disclosed invention, for which reference should be made to the appended claims. Additional aspects and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the aspects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In the following detailed portion of the present disclosure, the invention will be explained in more detail with reference to the example embodiments shown in the drawings, in which:

[0034] Figure 1 illustrates an exemplary RF signal power combiner assembly incorporating aspects of the disclosed embodiments;

[0035] Figure 2 illustrates hollow waveguide structures supporting pure-mode waves; [0036] Figure 3 illustrates waveguide structures for a power combiner assembly incorporating aspects of the disclosed embodiments;

[0037] Figure 4 illustrates an cross-sectional view of an axially symmetric structure supporting hybrid waves for a power combiner assembly incorporating aspects of the disclosed embodiments;

[0038] Figures 5 and 6 illustrate an electromagnetic field of the lowest dominant hybrid wave HEn in the cross-section of an ASPS structure for a power combiner assembly incorporating aspects of the disclosed embodiments;

[0039] Figures 7 and 8 illustrate exemplary coupling loops for a power combiner assembly incorporating aspects of the disclosed embodiments;

[0040] Figures 9 and 10 illustrate the employment of an electric wall and coupling loop assemblies in a power combiner assembly incorporating aspects of the disclosed embodiments;

[0041] Figure 11 illustrates a configuration of dielectric cards supporting coupling loops for a power combiner assembly incorporating aspects of the disclosed embodiments;

[0042] Figures 12 and 13 illustrate the employment of a magnetic wall and a coupling loop assembly for a power combiner assembly incorporating aspects of the disclosed embodiments;

[0043] Figures 14-15 illustrate perspective views of a power combiner assembly incorporating aspects of the disclosed embodiments; and

[0044] Figures 16-17 illustrate perspective views of an output portion of a power combiner assembly incorporating aspects of the disclosed embodiments; [0045] Figure 18 illustrates the use of a dielectric support member for a power combiner assembly incorporating aspects of the disclosed embodiments.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

[0046] The aspects of the disclosed embodiments are directed to an RF signal power combiner device configured to achieve high power levels in multi-beam antenna arrays. The combiner device is a multiport combiner employing hybrid azimuthally nonuniform electromagnetic waves using electric and/or magnetic walls associated with 3D field distribution in these waves. The electromagnetic properties of hybrid, azimuthally non-uniform waves supported by axially symmetrical periodical structures (ASPS) are employed for power combining. The term "hybrid wave" is used to designate a specific type of wave propagating in axially symmetrical periodic or quasiperiodic structures, generally referred to herein as "ASPS". The term reflects the distinguishing feature of these waves, of having both electric and magnetic longitudinal components, unlike other more common types of waves (TEM, TE, and TM waves). This property of hybrid waves is defined by the Hybrid Factor - a numerical indicator of the energy ratio between magnetic and electric partial components of longitudinal electromagnetic fields in the hybrid wave. In particular, the aspects of the disclosed embodiments exploit the features of the azimuthally non-uniform wave HEn in an ASPS for power combining.

[0047] By exploiting the properties of the electromagnetic fields of hybrid waves supported by specialized wave-guiding structures that can be used as an antenna array element, the power combining function can be integrated inside the antenna element. In one embodiment, the internal volume of the ASPS is compartmentalized into partial regions, or cells, defined by electric and magnetic walls. The electromagnetic fields inside the internal volume of the ASPS can be split into cells accordingly, with each cell fed by a dedicated coupling element. When the coupling elements feed with correct amplitudes and phases, a combination of energy occurs, providing the power combining effect.

[0048] Figure 1 illustrates one embodiment of an RF signal power combiner device 100 incorporating aspects of the disclosed embodiments. In this example, the combiner device 100 comprises a 2-to-1 combiner based on a Disk-on-Rod antenna structure 102, also referred to as an ASPS structure 102. The Disk-on-rod antenna structure belongs to the family of ASPS structures supporting hybrid waves and includes a corrugated rod antenna as the feeding end. The aspects of the disclosed embodiments find applications in cellular base stations and/or micro base stations that cover the 2-6GHz frequency range.

[0049] In the example of Figure 1 , the power combiner device 100 generally comprises a central conductor 106. Referring also to Figure 11 , in one embodiment, the central conductor 106 is disposed coaxially within the cylinder 120. In one embodiment, the cylinder 120 comprises an electrically conductive material, referred to herein as conductive cylinder 122. In the embodiment illustrated in Figure 13, the cylinder 120 comprises a dielectric material, referred to herein as dielectric cylinder 312. In the example of Figure 11 , a housing 20 surrounds the ASPS structure 102. One or more discs 104, forming part of the Disk-on-Rod structure 102, are disposed along a length of the central conductor 106 within the housing 20.

[0050] The central conductor 106 is defined by a pair of orthogonal symmetry planes 108, also referred to as the X and Y planes. Referring to Figures 1 and 5, for example, the symmetry planes are fixed at the longitudinal axis C of the central conductor 106. While there can be an infinite number of symmetry planes, there is only one pair that is orthogonal to each other. In the example shown in Figures 1 and 5, the pair of orthogonal symmetry planes 108 are defined by the X and Y planes through the approximate center or longitudinal axis C of the central conductor 106. This pair of symmetry planes defines the minimal order of the rotational symmetry for the central conductor 106 and defines a substantially square cross-section.

[0051] As shown in Figures 1 and 5, in one embodiment, the X plane defines a first symmetry plane 107 or horizontal cross-section through the central conductor 106. The first symmetry plane 107 contains the central axis that defines the orientation of the central conductor 106 and also contains the electric wall. The Y plane defines a second symmetry plane 109, or vertical cross-section through the central conductor 106. The second symmetry plane 109 contains the central axis that defines the orientation of the central conductor 106 and contains the magnetic wall. This set of conditions makes the pair of planes 107, 109 unique and independent on the order of symmetry limitations described with respect to Figure 3 below, because the pair of planes 107, 109 satisfy the conditions for the lowest order of symmetry specified, and are linked to the physical characteristics of the propagating wave.

[0052] Referring also to Figure 11 , one end of the cylinder 120 includes a shorting wall 110. In the example of Figure 11 , the shorting wall 110 closes one end of the cylinder 120. The central conductor 106 in the examples of Figures 8, 11 and 13 is electrically coupled to the shorting wall 110.

[0053] The shorting wall 110 is configured to electrically couple the central conductor 106 and an external conductor. In the example of Figures 8 and 11 , the cylinder 120 comprises a conductive cylinder 122, which forms the external conductor. The shorting wall 110 is electrically coupled to the conductive cylinder 122. In the example of Figure 15, the external conductor comprises the conductive cylinder 308. In this example, the shorting wall 110 is electrically coupled to the conductive cylinder 308.

[0054] The shorting wall 110 can be mechanically, galvanically or capacitively coupled to the external conductor. For example, the shorting wall 110 can be mechanically coupled to the conductive cylinder 122 of Figure 11 or the conductive cylinder 308 of Figure 15 to create the electrical coupling. In another embodiment, an air gap between the shorting wall 110 and the conductive cylinder 122, 308 forms an air filled capacitor, which creates the electrical coupling. For example, a portion of the central conductor 106 adjacent to the shorting wall 110 can be removed to form an air gap. As will be described below, a foam or dielectric member can be introduced into the gap for support. In alternate embodiments, any suitable manner of electrically coupling the shorting wall 110 and the external conductor can be used. In the example, of Figure 13, the shorting wall 110 is mechanically coupled to the dielectric cylinder 312.

[0055] As shown in Figure 1 , the central conductor 106 can include one or more slots 112 for placement of dielectric cards 114. The dielectric card 114 generally comprises a printed circuit board (PCB) or similar dielectric substrate on which conductive tracks or traces can be disposed, as that is generally known. Generally, the slots 112 will be disposed on opposing sides of the central conductor 106. The slots 112 in this example are generally aligned relative to or with a symmetry plane of the pair of orthogonal symmetry planes 108 that define the central conductor 106. In the example of Figure 1 , there are two slots 112 shown, each slot having a dielectric card 114 disposed therein. In alternate embodiments, the central conductor 106 can include any number of slots 112 to receive respective dielectric cards 114. [0056] Referring again to Figure 1 , the dielectric card 114 includes a coupling loop element 116, also referred to as a magnetic coupling loop element, on one side of the dielectric card 114. The coupling loop element 116 on the dielectric card 114 is generally aligned relative to a symmetry plane of the pair of orthogonal symmetry planes 108 that define the central conductor 106. In one embodiment, the combiner 100 will include at least a pair of coupling loop elements 116. In the example of Figure 1 , the coupling loop element 116 is in the form of a Figure-of-8 coupling loop. In alternate embodiments, the coupling loop element 116 can comprise any suitable loop structure.

[0057] An opposite or reverse side of the dielectric card 114 includes a conductive track or element 118, also referred to herein as a feed line. The conductive track or element 118 is configured to feed electrical signals from the respective input port P1 -P4 to the corresponding coupling loop element 116. In one embodiment, the coupling between the input ports P1 -P4 and the respective coupling loop element 116 is galvanic coupling. In alternate embodiments, the conductive track 118 can be coupled to the coupling loop element 116 in any suitable manner other than including galvanic coupling. For example, in one embodiment, the conductive track 118 can be coupled to the coupling loop element 116 via a capacitive coupling device, such as a capacitor.

[0058] The power combiner 100 further includes an output port 130. In the examples of Figure 1 and 16, the output port 130 is disposed on an end of the combiner 100 away from or opposite the shorting wall 110. The output port 130 is configured to output a combined power of the signals from the plurality of input ports P1 -P4.

[0059] The aspects of the disclosed embodiment exploit the properties of hybrid, azimuthally non-uniform waves supported by axially symmetrical periodical structures, such as the combiner device 100 shown in Figure 1. To allow for dual polarized operation, the antenna aperture in the combiner device 100 should have a certain degree of symmetry. This can be expressed in terms of the order of axial symmetry used in crystallography: C₄, Ce, C16, ... C∞. However, this limits the choice of suitable antenna structures.

[0060] Figure 2 illustrates exemplary antenna aperture structures 10 based on hollow waveguides supporting pure-mode waves H_mn and E_mn. A common advantage of these simple structures is they all have a low frequency cut-off, providing considerable rejection for frequencies below cut-off, unlike printed dipole / slot antenna aperture structures. Unfortunately, these simple structures can be too bulky to be packed in the antenna array, particularly if scanning requirements apply, as inter element distances become too great. To overcome this limitation, a second conductor can be positioned co- axially to the first one.

[0061] Figure 3 illustrates exemplary aperture cross-sections of hybrid mode guiding structures having a second conductor 14 positioned co-axially with the first conductor 12. These types of axially symmetrical structures may support propagation of pure modes H_mn, E_mn, and also include a subset supporting the hybrid modes HE_mn and EHmn. These modes propagate at a certain wavelength associated with the cross sectional dimensions.

[0062] Figure 4 illustrates a longitudinal cross-section of an exemplary hybrid mode guiding or ASPS structure 102. The ASPS structure 102 in Figure 4 is a generalized ASPS structure, and for simplicity is shown with only one of two conductors containing corrugations 103. Practical engineering solutions can be based on simpler versions derived from this generalized configuration. For example, with d=0 the ASPS structure 102 degenerates to a circular waveguide of radius e. With g2=g1 =gN the ASPS structure 102 becomes a smooth wall coaxial antenna structure. With I I =I2=IN and e→∞ the ASPS structure 102 becomes a corrugated coaxial ASPS, also known as Disk-on-Rod antenna. The main advantage of this class of guiding structures is the possibility to support HE_mn hybrid waves having not only one, but two cut-off frequencies, a low cut-off frequency and a high cut-off frequency.

[0063] Referring to Figures 5 and 6, the electromagnetic field or field structure of the lowest azimuthally non-uniform wave HEn in the cross-section of the ASPS structure 102 is illustrated. In this example, it is assumed that the longitudinal axis Z is the symmetry axis of the ASPS structure 102. In Figure 6, the cross section is aligned with axis Z. In the example of Figure 5, X, Y are the orthogonal pair of axis.

[0064] Figure 5 also illustrates the magnetic fields or magnetic field vectors 532 orthogonal to axis Z. The magnetic field vectors 532 in Figure 5 are shown by dashed lines. In Figure 6, the cross-section of the magnetic field vectors 532 are represented by elements 531 and 533. Elements 533 show the magnetic field vectors 532 crossing into the image and elements 531 show the magnetic field vectors 532 crossing out of the image.

[0065] The electric field vectors 522 in Figures 6 are shown in bold, solid lines. In Figure 5, the cross-section of the electric field vectors 522 of Figure 6 are represented by elements 521 and 523. Elements 523 show the electric field vectors 522 crossing into the image, while the elements 521 show the electric field vectors 522 crossing out of the image. Since the wave HEn is an azimuthally non-uniform wave, there are areas with maximum longitudinal electric field strength (at cp=90 and cp=270 degrees) and areas where the electric field component does not exist (at cp=0 and cp=180 degrees). [0066] Also, the field distribution shown in Figures 5 and 6 indicates the existence of electric walls 524 and magnetic walls 534 which are the surfaces orthogonal to the electric or magnetic vectors, correspondingly. The position and configuration of the electric walls 524 and magnetic walls 534 are specifically attributed to the particular operating mode, which in this example is the lowest azimuthally non-uniform wave HEn.

[0067] The aspects of the disclosed embodiments exploit the features of the azimuthally non-uniform wave HEn for power combining. In one embodiment, the internal volume of the ASPS structure 102 of Figure 1 is compartmentalized into partial regions, or cells, defined by electric walls 524 and magnetic walls 534. For example, the field distribution in Figure 5 shows the properties of symmetry. The symmetry planes are co- located with the electric and magnetic walls 524, 534. The electric field 522 has a counter-symmetry plane located at the plane cp=0 (electric wall). This is the surface where no tangential electric field exists, i.e. all electric field lines are orthogonal to the electric wall 524. The overall electric field distribution is counter-symmetrical relative to the electric wall 524 at cp=0 and the magnetic field distribution is symmetrical relative to the electric wall 524.

[0068] In one embodiment, referring also to Figures 7 and 8, the volume of ASPS structure 102 can be split into two compartments, generally referred to herein as an upper compartment 140 and a lower compartment 150, relative to the electric wall 524. The upper compartment 140 and the lower compartment 150 are separated by electric wall 524 located in the plane cp=0. As is shown in Figure 8, both the upper compartment 140 and the lower compartment 150 can be fed with one or more dedicated coupling elements 116 and corresponding feed lines 118, which are coupled to corresponding inputs P1 , P2 and P3, P4, shown in Figure 1. [0069] In the example of Figure 5, the magnetic field 532 will have a counter- symmetry plane, a magnetic wall 534, located at cp=90 degrees. This is the surface where no tangential magnetic field 532 exists, i.e. all magnetic field lines are orthogonal to the magnetic wall 534. The overall magnetic field distribution is counter symmetrical relative to the magnetic wall 534 at cp=90 degrees. The electric field distribution is symmetrical relative to the magnetic wall 534.

[0070] In one embodiment, referring to Figure 7, the volume of the ASPS structure 102 can also be treated as two "separate" compartments, one compartment 220 to the left and one compartment 230 to the right of the magnetic wall 534. The electromagnetic field inside each compartment 220, 230 can be excited by a suitable coupling element, such as coupling loop element 116 fed by a corresponding feed line, such as feed line 118. Thus, with reference to Figure 5, the volume of the ASPS structure 102 is treated as a plurality of compartments or cells, an upper 140 and lower 150 compartment, a left compartment 220 and a right compartment 230.

[0071] The compartments 140, 150, 220, 230 referred to above, are not exactly 'separate', but rather have to contain coherent fields, as their phase and amplitudes have to be chosen to reconstitute the overall field distribution of the required mode HEn. When this condition is fulfilled the power combining effect is achieved.

[0072] When coupling elements 116 are fed with the correct amplitudes and phases, a combination of the energy is occurring, providing the power combining effect. These principles are also applicable to the higher azimuthally non-uniform waves HE_mn. With the higher azimuthally non-uniform waves HE_mn the locations of the electric 524 and magnetic walls 534 have to be adapted accordingly. [0073] As shown in Figure 1 , a coupling loop element 116 is disposed in each of the upper compartment 140 and the lower compartment 150. In one embodiment, the coupling loop element 116 is a magnetic loop coupling element that couples to the magnetic field inside the respective cell or compartment 140, 150. One example of a coupling loop element 116 is shown in Figure 9. Figure 10 illustrates the coupling loop element 116 and the associated magnetic field 132. The coupling loop element 116 shown in Figures 9 and 10 has the forward and the return directions of magnetic flux and the most efficient coupling is achieved when coupled in both directions. One example of such a coupling element is a "Figure-of-8" coupling loop topology. In the example of Figure 10, each part or loop 116a, 116b of the 'Figure-of-8' coupling loop is generating magnetic flux of equal strength, but in opposite directions. In alternate embodiments, any suitable type of coupling element can be used to couple to the cells, other than including a magnetic loop coupling element 116.

[0074] As shown in the examples of Figures 1 and 8, at least one coupling loop element 116 is positioned in each compartment 140, 150. The configuration shown in Figure 1 provides a minimal 1 +1 differential feeding arrangement of the input ports P1 - P4, forming a 2 (differential)-to-l combiner with two differential input ports feeding the power into the common output port 130 supporting the required mode HEn. Placing more than one coupling loop element 116 will give further increase to the number of input ports yielding combiners with input ports configured as 1 +1 (differential), 2+2(differential), ..., 4+4(differential) et cet. The combiner 100 of the disclosed embodiments provides a multi- port combining function.

[0075] Figures 7 and 8 illustrate an exemplary realization of employing an electric wall 524 in a multi-port power combiner 100 incorporating aspects of the disclosed embodiments. In the cross-sectional view of Figure 8, the ASPS structure 102 is shown disposed within the confines of the conductive cylinder 122. Pairs of coupling loop elements 116 are disposed within the conductive cylinder 122, on one side of the shorting wall 110. The coupling loop elements 116 are positioned symmetrically with relation to the electric wall 524 (shown by the solid bold line) and orthogonally to magnetic field lines 532 (shown by the dashed lines). The coupling loops 116 maintain the correct phasing according to the phasing of magnetic field lines 532 forming closed loops symmetrical to the electric wall 524. As illustrated in Figure 7, the number of coupling loops 116 in this example, each supported on a dielectric card 114, is eight. In one embodiment, each coupling loop 116 requires a pair of coaxial connectors for input, such as inputs P1 and P2 or inputs P3 and P4. The inputs P1 -P4 are connected to respective feed lines 118.

[0076] In practice, referring to Figures 1 and 7, each pair or set of coupling loops 116 can be printed or otherwise disposed on a dielectric card 114. As shown in Figure 1 , the dielectric cards 114 are mounted in the corresponding supporting slots 112 of the ASPS structure 102.

[0077] The number of single-ended input ports P1 -P4 in the example of Figure 1 is double the number of differential ports: 2+2 (single ended), 4+4 (single ended),..., 8+8 (single ended). The number of coupling loops 116 is limited by the specified level of insertion loss, cross coupling (isolation) between ports, breakdown voltages and design limitations to the sizes of the feeding lines, as well as technological complexity. In one embodiment, the power combiner 100 can be converted into a single-ended configuration, with the middle point of each coupling loop 116 connected to a ground potential by a dedicated connection. [0078] Figure 11 illustrates a 4-input single-ended feeding arrangement of the input ports P1-P4, forming a 4(single-ended)-to-1 combiner with four single ended input ports. In this example, there are four dielectric cards 114 disposed with respect to the central conductor 106. The slots 115 in the dielectric cards 114 support one or more discs 104 of the ASPS structure 102. The coupling loops 116 are connected to the input ports P1 - P4 disposed in respective openings 111 on one end, and to the ground on another end. In this example, one end of the coupling loop 116 is electrically connected to electrical ground, which in this example is the conductive cylinder 122. In this embodiment, the central conductor 106 is shown as connected to the shorting wall 110. In alternate embodiments, the shorting wall 110 is not connected to the central conductor. The use of the conductive cylinder 122 as the ground connection forms a single ended coupling configuration. The energy fed by the input ports P1 -P4 is combined into the common output port 130 that supports the required mode HEn.

[0079] Figures 12-15 illustrate another example of a power combiner 300 incorporating aspects of the disclosed embodiments. In this example, the ASPS structure 302 divided into compartments or cells, generally indicated as a left compartment 320 and a right compartment 330, separated by the magnetic wall 332 located at the plane cp=90.

[0080] Figures 12-15 illustrate the use of a dielectric cylinder 312. In this example, the dielectric cylinder 312 is comprised of a flexible PCB rolled into a cylinder. In one embodiment, the dielectric cylinder 312 can be 3D printed with layers of plastic or other dielectric with two or more metal layers (electrochemically) deposited in-between plastic layers. [0081] Magnetic loops 316 are used to couple to the magnetic field inside the respective cells 320, 330. The magnetic field distribution is shown in Fig. 12. The two closed loops 334, 336 shown in dashed lines representing the magnetic field are split into two equal halves by the magnetic wall 332.

[0082] Each compartment 320, 330 contains a pair of such 'halves' having a common part of the magnetic flux co-located with the electric wall 322 at and around the plane cp=0. At least one coupling loop 316 is positioned in the respective compartment 320, 330. This will give at least 1 +1 (differential), 2+2 (differential), ..., 4+4 (differential) combiners.

[0083] In the exemplary power combiner 300 shown in Figures 12-15, a number of coupling loops 316, which in this example are magnetic coupling loops, can be implemented. As shown in the example of Figure 12, the coupling loops 316 are positioned symmetrically with relation to the magnetic wall 332 and orthogonally to the plane of electric wall 334. In the embodiment shown in Figure 12, the magnetic coupling loops 316 are printed on a surface of the dielectric cylinder 312. In one embodiment, the magnetic coupling loops are printed on an outer surface of the dielectric cylinder 312. In the embodiment, wherein the dielectric cylinder 312 is 3D printed with layers of plastic or other dielectric with two or more metal layers (electrochemically) deposited in-between plastic layers, the coupling loops 316 can be printed on the different layers to provide for a plurality of stacked coupling loops 316. The cylinder 312 can also be replaced by any shape as soon as it has the symmetry or order C₄, Ce, Ci6, ... C∞, as mentioned above with respect to Figure 3. Vias 313, such as those shown in Figure 15, may be formed in due course by laser-cutting or drilled and then electroplated in each layer to connect parts of the coupling loops between each other and/or to the corresponding input lines 318. [0084] The coupling loops 316 should maintain correct phasing accordingly to the actual phasing of the magnetic lines forming closed loops 334, 336 symmetrical to the electric wall 322. The number of coupling loops 316 in this example is eight, with a pair of input connectors P1 , P2 associated with each coupling loop 316.

[0085] Referring also to Figure 13, in this example, the coupling loop 316 and corresponding feeding conductor or track 318 are respectively disposed on the outer and inner surfaces of the dielectric cylinder 312. The dielectric cylinder 312 is fixed inside the ASPS structure 302 in a dedicated position. The combiner 300 shown in Figure 13 is a 2- to-1 combiner realization based on a Disk-on-Rod antenna. P1 -P4 are the input ports of the combiner 300, while 304 is the corrugated rod or end side of the Disk-on-Rod antenna structure 302. A central conductor 306 is disposed co-axially inside the dielectric cylinder 312.

[0086] The conductive tracks 318 on the inner surface of the dielectric cylinder 312 are configured to feed signals from the respective input ports P1 , P2 and P3, P4 to the corresponding coupling loop 316. The combiner 300 can also be converted into a single ended configuration by connecting the middle point of each coupling loop 316 to ground by a dedicated connection. Unlike in the power combiner 100 shown in Figure 1 , converting the configuration of Figure 13 into a single ended one is more difficult, as the coupling loops 316 are not "Figure-of-8" types of coupling loops and do not have a natural ground point.

[0087] In one embodiment, the number of coupling loops 316 is limited by the particular mode (typically the lowest dominant azimuthally non-uniform mode HEn) and the specified level of isolation between ports, insertion loss, breakdown voltages and design limitations to the sizes (cross section) of the feeding lines, as well as technological complexity (production cost).

[0088] Figures 14 and 15 illustrate an exemplary power combiner 300 incorporating aspects of the disclosed embodiments where the number of input loops 316 is reduced to only two input loops 316. The plurality of input ports P1 -P4 extend through respective openings 311 in the shorting wall 310. The ends 340 of each loop 316 is connected to a corresponding or dedicated input port P1 -P4 through a section of coaxial line (not shown). Conductive feed tracks 318 are disposed on one or more of an outer and inner surface of the dielectric cylinder 312. The vias 313 connect parts of the coupling loops 316 located on the opposite (inner and outer) surfaces of the dielectric cylinder 312.

[0089] In the example of Figure 15, the dielectric cylinder 312 is disposed co-axially within the conductive cylinder 308. A shorting wall 310 closes an end of the conductive cylinder 308. In this example, the shorting wall 310 is electrically coupled to the conductive cylinder 308 and the central conductor 306.

[0090] In the examples of Figures 14 and 15, at least one pair of magnetic loop coupling elements 316 are disposed on a surface of the dielectric cylinder 312. For example, the magnetic loop coupling elements 316 can be printed on the surfaces of the dielectric cylinder, such as one or more of an outer surface and inner surface. In one embodiment, the magnetic coupling loop elements 316 can also be positioned within the walls, or between the outer and inner surfaces, of the dielectric cylinder 312, such as in a multi-layer flexy design or 3D printed design, as described above.

[0091 ] Figure 16 illustrates an example of an output port 130 for a power combiner incorporating aspects of the disclosed embodiments. In this example, the output port 130 is the cross-section of the ASPS used in a particular realization. In the case of a disk-on- rod structure, such as shown in Figure 1 , the output port 130 is the cross-section of the disk-on-rod structure a combination of the input signals, or the combined power of the input signals, propagate along the ASPS structure 102. Since the cross section is restricted by the conductive cylinder 122 (from the outside) there is no radiation happens there, only propagation along the ASPS structure 102. In one embodiment, this cross section or output port 130 can be an input to a subsequent filtering structure, an antenna, phase shifter or other suitable components. While the input ports P1 -P4 are coaxial input ports providing input signals, at the output port 130, a travelling wave is formed that propagates away from the combiner and the energy is contained within the cross section of the ASPS structure 102. If the ASPS structure 102 is transitioning into more conventional transmission line, such as a waveguide, the output port 130 is contained within the cross section of the output waveguide 402, as in shown Figure 17. Figure 17 illustrates a 4-port power combiner 400 with a transition to a circular waveguide portion 402. In the example of Figure 17, the output port 130 is the cross-section of the circular waveguide 402.

[0092] Figure 18 illustrates the power combiner of the disclosed embodiments transitioning to a circular waveguide portion 402. In the embodiment of Figure 18, the ASPS structure 102 is supported by a dielectric support member 404, such as a dielectric foam. In this example, the dielectric foam 404 surrounds and isolates the ASPS structure 102 from the conductive cylinder 122. Since the low frequency cut-off of the circular waveguide 402 is considerably higher than the cut-off of ASPS structure 102, the section of circular waveguide 402 provides additional out-of-band rejection on the lower side of the operating frequency range. The remaining empty section between the shorting wall 110 and the ASPS structure 102 provides more volume to position additional coupling loops and/or for increasing the area of each coupling loop. Also, this configuration has the advantage of assembly from the two sides of the antenna array. The external conductive cylinder 122 is part of the antenna array that has to be assembled with all components for each element. With no electrical connection required between the shorting wall 110 and the ASPS structure 102, the ASPS structure, or disk-on-rod section 102 can be assembled from the front of the antenna array. The other portions of the combiner can be assembled from the back. In one embodiment, the dielectric support 404 forms a dielectric spacer that can be used as a plastic radom for sealing the inside of the combiner.

[0093] The aspects of the disclosed embodiments are directed to power combining based on the properties of the guided waves supported by ASPS. The multiport combiner of the disclosed embodiments employs hybrid azimuthally nonuniform electromagnetic waves using electric and/or magnetic walls associated with 3D field distribution in these waves. Coupling is realized using magnetic coupling elements. An even number of coupling loops are positioned symmetrically with relation to a magnetic wall in the plane or a curved surface co-linear with the magnetic wall. The number of turns and mutual direction of turns in the coupling loops are arranged to maintain a correct coupling factor and phasing according to the mutual phasing of magnetic lines of the required propagating mode. It is not necessary to have input signals in counter phase as the in-phase signals can be combined with coupling loops providing necessary phase shift by altering the direction of winding.

[0094] The aspects of the disclosed embodiments leads to an increased number of ports, improved isolation, insertion loss, and integrating the power combining function into the antenna element. The properties of the dominant hybrid wave ensure additional isolation inside the combiner. If combiner is integrated into the filter that is designed based on the hybrid mode, the coupling requirements will be defined by the corresponding elements of the coupling matrix. This will advantageously lead to reduction in the overall coupling levels required from the combiner. If combiner is integrated into the filtering structure supporting the hybrid mode, for example, a band pass filter based on ASPS, the coupling requirements will be defined by the corresponding elements of the coupling matrix of the filter.

[0095] Thus, while there have been shown, described and pointed out, fundamental novel features of the invention as applied to the exemplary embodiments thereof, it will be understood that various omissions, substitutions and changes in the form and details of devices and methods illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the invention. Further, it is expressly intended that all combinations of those elements, which perform substantially the same function in substantially the same way to achieve the same results, are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

CLAIMS What is claimed is:

1. A radio frequency (RF) signal combiner (100), the combiner (100) comprising:

an axially symmetric periodic waveguide device (102), the axially symmetric periodic waveguide device (102) comprising:

a cylinder (120);

a central conductor (106) disposed coaxially within the cylinder (120), the central conductor (106) defined by a pair of orthogonal symmetry planes (108); and

a shorting wall (1 10) closing an end of the cylinder (120) and being electrically coupled to the central conductor (106);

at least one pair of magnetic loop coupling elements (1 16) disposed within the cylinder (120) relative to a symmetry plane of the pair of orthogonal symmetry planes (108) defining the central conductor (106);

a plurality of input ports (P1 , P2, P2, P4) extending through respective openings (1 1 1 ) in the shorting wall (1 10), a respective one of the plurality of input ports (P1 , P2, P3, P4) feeding a signal to a corresponding one of the at least one pair of magnetic loop coupling elements (1 16); and

an output port (130), the output port (130) disposed on a side of the combiner (100) away from the shorting wall (1 10), the output port (130) configured to output a combined power of signals from the plurality of input ports (P1 , P2, P3, P4).

2. The radio frequency signal combiner of claim 1 , wherein the cylinder (120) comprises a conductive cylinder (122) and the at least one pair of magnetic loop coupling elements (1 16) is supported on a dielectric card (1 14).

3. The radio frequency signal combiner (100) of claim 2, wherein the at least one pair of magnetic loop coupling elements (1 16) is arranged, preferably printed, on a first side of the dielectric card (1 14).

4. The radio frequency signal combiner (100) of any one of claims 2-3, wherein a pair of the at least one pair of magnetic loop coupling elements (1 16) are disposed co- planar with each other and with the symmetry plane.

5. The radio frequency signal combiner (100) of any one of claims 2-4, wherein a first magnetic loop element of the co-planar pair of magnetic loop coupling elements (1 16) is disposed equidistant from a second magnetic loop coupling element of the co- planar pair of magnetic loop coupling elements (1 16) relative to the central conductor (106).

6. The radio frequency signal combiner (100) of any one of claims 2-5, comprising a conductive track (1 18) on a second side of the dielectric card (1 14), the conductive track (118) being coupled to the respective one of the plurality of input ports (P1 , P2, P3, P4).

7. The radio frequency signal combiner of any one of claims 2-6, wherein the dielectric card (1 14) is disposed in a dielectric card receiving slot (1 12) of the central conductor (106).

8. The radio frequency signal combiner (100) of any of claims 1 to 7, wherein magnetic loop coupling elements of the at least one pair of magnetic loop coupling elements (1 16) comprise figure-of-eight magnetic loop coupling elements.

9. The radio frequency signal combiner of any of claims 1 to 8, wherein at least a first symmetry plane of the pair of orthogonal symmetry planes (108) defining the central conductor (106) crosses all magnetic loop coupling elements of the at least one pair of magnetic loop coupling elements (1 16).

10. The radio frequency signal combiner (100) of claim 1 , wherein the cylinder (120) comprises a dielectric cylinder (312) and magnetic loop coupling elements (316) of the at least one pair of magnetic loop coupling elements (1 16) are arranged, preferably printed, on a surface of the dielectric cylinder (312).

1 1. The radio frequency signal combiner (100) of claim 10, comprising conductive tracks (318) arranged, preferably printed, on a surface of the dielectric cylinder

(312), the conductive tracks (318) being coupled to the respective one of the plurality of input ports (P1 , P2, P3, P4) for feeding the signal to the corresponding one of the magnetic loop coupling elements (316).

12. The radio frequency signal combiner (100) of any claims 10 or 1 1 , wherein the magnetic loop coupling elements (316) are disposed equidistant from each other relative to the central conductor (306).

13. The radio frequency combiner (100) of any of the preceding claims, wherein the axially symmetric periodic waveguide device (102) supports a hybrid wave signal.

14. The radio frequency combiner (100) of any of the preceding claims, wherein an internal volume of the axially symmetrical periodic waveguide device (102) is divided by the pair of orthogonal symmetry planes (108) into at least one pair of compartments (140, 150), wherein a compartment of the at least one pair of compartments (140, 150) has a dedicated magnetic loop coupling element and an input port.

15. The radio frequency combiner (100) of any of the preceding claims, wherein the axially symmetric periodic hybrid waveguide device (102) is a disk-on-rod antenna assembly.