Waveguide device with ridge extension

Abstract

A waveguide device for transmitting or receiving RF signals is provided. The device includes a waveguide element, a crown, and one or more ridge elements. The waveguide element has a waveguide element aperture and a guided wave interface. The crown includes one or more crown elements disposed on the waveguide element at a radiated wave interface of the waveguide device such that the crown elements extend beyond the waveguide element aperture. The one or more ridge elements are disposed on an interior surface of the waveguide element and run along a portion of or the entire length of the waveguide element from the guided wave interface to the waveguide element aperture and are supported by the crown elements beyond the waveguide element aperture. The crown and one or more ridges form an effective aperture of the waveguide device beyond the waveguide element aperture and ease the transition into free space.

Description

WAVEGUIDE DEVICE WITH RIDGE EXTENSIONTechnical Field

[0001] The following relates generally to waveguide devices for transmitting radio frequency (RF) signals, and more particularly to waveguide devices for use in space applications.Introduction

[0002] For electrically small waveguides, the interface between the waveguide aperture and free-space acts as a step impedance, reflecting a significant amount of energy. In a circular polarized system, this can lead to issues related to isolation between the two ports. In a linearly polarized system, this would degrade the impedance match of the element. In both cases, the transmission of the element decreases as energy has trouble making the transition to free space, degrading overall system performance.

[0003] The initial problem was related to removing leaky waves propagating across the surface of an antenna array. A 2021 paper (“Scan Blindness Free Design of Wideband Wide-Scanning Open-Ended Waveguide Phased Array”) showed that external aperture features can improve the scan-blindness by changing the surface impedance of the antenna while still allowing for good radiation properties.

[0004] Dielectrically stuffed waveguides with a dielectric “impedance-gradient structure” can achieve a good free space match. However, dielectrics are avoided for space applications where possible due to outgassing risk and corona.

[0005] For earthbound arrays with electrically small apertures, a wide variety of options present themselves to solve the problem of free space matching, such as using dielectrics to lower the cut-off of the pertinent waveguide modes. Such solutions are straightforward and effective but not viable for space applications.

[0006] In terms of space applications, there are more and more satellites being deployed in lower orbits (MEO, LEO). This creates a need for a wider scan angle than their GEO counterparts, as the earth appears as larger in these lower orbits. This in turn means that the element spacing of the array must be carefully considered so that gratinglobes do not appear within the scan area, which limits the aperture size of an individual element of the array.

[0007] Accordingly, there is a need for an improved waveguide device that overcomes at least some of the disadvantages of existing systems and methods.Summary

[0008] A waveguide device for transmitting or receiving radio frequency (RF) signals is provided. The waveguide includes: a waveguide element including a waveguide element aperture and a guided wave interface; a crown comprising one or more crown elements disposed on a surface of the waveguide element at a radiated wave interface of the waveguide device such that the crown elements extend beyond the waveguide element aperture; and one or more ridge elements disposed on an interior surface of the waveguide element and running along a portion of or the entire length of the waveguide element from the guided wave interface to the waveguide element, the ridge elements supported by the crown beyond the waveguide element aperture.

[0009] In an embodiment, the crown and the one or more ridges form a radiating aperture of the waveguide device beyond the waveguide element aperture.

[0010] In an embodiment, the waveguide element includes a plurality of waveguide element walls and at least one of the one or more ridge elements is disposed at a junction between two adjacent waveguide element walls.

[0011] In an embodiment, the one or more ridge elements includes a plurality of ridge elements with identical shape and size.

[0012] In an embodiment, the one or more ridge elements include at least two ridge elements with different shapes or different dimensions.

[0013] In an embodiment, the waveguide element includes a plurality of waveguide element walls and at least one of the plurality of waveguide element walls has at least two of the one or more ridge elements disposed thereon.

[0014] In an embodiment, the number of crown elements is equal to the number of ridge elements.

[0015] In an embodiment, the one or more ridge elements are centered on the one or more crown elements.

[0016] In an embodiment, the waveguide element includes a plurality of waveguide element walls and each of the one or more crown elements is centered on a respective waveguide element wall.

[0017] In an embodiment, the waveguide element has a hexagonal cross-section with six walls.

[0018] In an embodiment, the waveguide element has a rectangular or square cross-section.

[0019] In an embodiment, the waveguide element has a circular cross-section.

[0020] In an embodiment, the waveguide element has an inner cross-section and an outer cross-section that are different.

[0021] In an embodiment, the waveguide device includes six crown elements and six ridge elements, and each wall of the waveguide element has one crown element and one ridge element disposed thereon.

[0022] In an embodiment, each of the one or more ridge elements includes a first side edge integral with an inner wall of the waveguide element and a second side edge facing an inner cavity formed by the inner wall of the waveguide element.

[0023] In an embodiment, the second side edge is curved.

[0024] In an embodiment, a profile of the second side edge is the same along the entire length of the second side edge.

[0025] In an embodiment, a profile of the second side edge varies along the length of the second side edge.

[0026] In an embodiment, the second side edge has a straight portion and a curved portion.

[0027] In an embodiment, the profile of the second side edge is stepped.

[0028] In an embodiment, the waveguide element includes one or more walls defining an inner cavity of the waveguide element, each of the one or more ridge elements is disposed on at least one of the one or more walls, and each of the one or more ridge elements is orthogonal to the wall on which the respective ridge element is disposed.

[0029] In an embodiment, the waveguide element includes one or more walls defining an inner cavity of the waveguide element, each of the one or more ridge elements is disposed on at least one of the one or more walls, and each of the one or more ridge elements is not orthogonal to the wall on which the respective ridge element is disposed.

[0030] In an embodiment, the waveguide element includes one or more walls defining an inner cavity of the waveguide element, and the number of crown elements is greater than the number of walls.

[0031] In an embodiment, the one or more crown elements is a plurality of crown elements that are identical in shape and size.

[0032] In an embodiment, the one or more crown elements are triangular or trapezoidal.

[0033] In an embodiment, the one or more crown elements each include a pointed tip.

[0034] In an embodiment, the one or more crown elements each include a rounded tip.

[0035] In an embodiment, the waveguide element includes one or more walls defining an inner cavity of the waveguide element, and the number of ridge elements is greater than the number of walls.

[0036] In an embodiment, the waveguide device is fed by a coaxial line or probe that excites a mode in the waveguide element.

[0037] In an embodiment, the guided wave interface is a guided wave feed point, and a guided wave at the guided wave feed point is orthogonal to a radiated wave at the radiated wave interface.

[0038] In an embodiment, the waveguide element has a stepped profile, and the one or more ridges have a stepped profile that follows the stepped profile of the waveguide element.

[0039] In an embodiment, the waveguide element uses energy coupling.

[0040] In an embodiment, at least one of the one or more ridge elements protrudes beyond a wall of the waveguide element into an interior of the waveguide element at the radiated wave interface to support wave coupling.

[0041] An array antenna is also provided that includes a plurality of any of the waveguide devices described above arranged in an array.

[0042] A waveguide probe is also provided that includes any of the waveguide devices described above.

[0043] Other aspects and features will become apparent, to those ordinarily skilled in the art, upon review of the following description of some exemplary embodiments. Brief Description of the Drawings

[0044] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification. In the drawings:

[0045] Figures 1A-1D are front perspective, cross-sectional front perspective, bottom perspective, and top views of a waveguide device, according to an embodiment;

[0046] Figures 2A-2B are perspective and top views, respectively, of the waveguide element of Figures 1A-1D in isolation;

[0047] Figure 3A is a perspective view of the crown of Figures 1 A-1 D in isolation;

[0048] Figure 3B is a perspective view of a crown element of Figures 1A-1D in isolation;

[0049] Figure 4 is a side view of a ridge element of Figures 1 A-1 D in isolation;

[0050] Figures 5A-5C are top, perspective, and cross-sectional perspective views of an antenna array including a plurality of the waveguide devices of Figures 1A-1D, according to an embodiment;

[0051] Figure 6 is a cross-sectional schematic diagram of a waveguide device, according to an embodiment;

[0052] Figure 7 is a cross-sectional schematic diagram of a waveguide device, according to another embodiment;

[0053] Figure 8 is a cross-sectional schematic diagram of a waveguide device, according to another embodiment; and

[0054] Figure 9 is a cross-sectional schematic diagram of a waveguide device, according to another embodiment.Detailed Description

[0055] Various apparatuses or processes will be described below to provide an example of each claimed embodiment. No embodiment described below limits any claimed embodiment and any claimed embodiment may cover processes or apparatuses that differ from those described below. The claimed embodiments are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below.

[0056] The following relates generally to a waveguide device, and more particularly to a waveguide device with a ridge extension beyond an aperture of a waveguide element of the waveguide device. The waveguide device may be particularly well suited to use in an array, which may provide improved performance of the array. The waveguide device may be used as an array element in an array, such as a phased array, or may be used as a small waveguide probe (e.g., single waveguide device).

[0057] The waveguide device includes a waveguide element, a crown comprising one or more crown elements, and one or more ridge elements. The waveguide element includes a waveguide element aperture and a guided wave interface. The crown elements are disposed on a surface of the waveguide element at the waveguide element aperture such that the crown elements extend beyond the waveguide element aperture. The one or more ridge elements are disposed on an interior surface of the waveguide element, run along a length of the waveguide element from the guided interface to the waveguideelement aperture (the entire length or a portion of the entire length), and extend beyond the waveguide element aperture. The guided interface may or may not be in line with the radiating interface, where “in line” refers to “following the propagation of the conducted wave inside the device (as opposed to the direction of radiation of the waves outside the device). The ridge elements are supported by the crown elements beyond the waveguide element aperture. The waveguide device includes an effective aperture (or radiating aperture) that is beyond the waveguide element aperture.

[0058] As used herein, the term “guided interface” or “guided wave interface” refers to an interface of the waveguide device through which a wave being guided inside the device enters or exits the device in a guided manner (e.g., in contrast to radiation through free space). This is to contrast with the radiating interface (or radiative wave interface) of the device, which is an interface at which the radiated wave is transmitted or received (i.e. , at the radiation aperture). As will be seen, the position or configuration of the guided wave interface relative to the radiative wave interface may vary in embodiments. Accordingly, the relationship between a radiated wave propagation direction and a guided wave propagation direction in the waveguide device may vary in different embodiments. In fact, in some cases, the guided wave propagation direction may itself vary along the length of the waveguide device (e.g., where the waveguide device has a stepped profile).

[0059] Referring now to Figures 1A-1 D, shown therein is a waveguide device 100, according to an embodiment. Select components of the waveguide device 100 are shown in isolation in Figures 2A-4, which will be referred to simultaneously.

[0060] The waveguide device 100 may be used to transmit or receive RF signals. Multiple instances of the waveguide device 100 may be used as antenna elements in an array antenna, such as a phased array or direct radiating array. An example of such an array is shown in Figures 5A-5C, where array 500 includes multiple instances of waveguide device 100. The waveguide device 100 may also be used on its own, for example as a single waveguide probe. The waveguide device 100 may be produced as a single piece (e.g., by additive manufacturing).

[0061] The waveguide device 100 includes a waveguide element 102, a crown 104 including one or more crown elements 106, and one or more ridge elements 108. Whilethe embodiment of waveguide device 100 shown in Figures 1A-1D includes a plurality of crown elements 106 and a plurality of ridge elements 108, embodiments with one crown element 106 and / or one ridge element 108 are contemplated by the present disclosure and may be used, for example, where a specific or reduce mode or scan direction is needed. Generally, the crown 104 is an extension of the waveguide element 102 wall (i.e., surfaces are parallel) and the ridge elements 108 are orthogonal to the crown 104 and waveguide element 102. The ridge elements 108 extend beyond an aperture of the waveguide element 102 (aperture 216 of Figure 2A), which eases the transition into free space. The crown 104 provides support for the ridge elements 108, aids in active matching, and breaks up leaky waves propagating across the surface of the array (when the device 100 is used in an array).

[0062] The waveguide device 100 uses the crown 104 around the waveguide element aperture to remove surface waves causing scan blindness. The combination of the crown 104 with the ridges 108 extending onto the crown 104 has been shown to provide good RF performance such as active match, radiation efficiency, and low cross-polarization level.

[0063] The waveguide device 100 includes a radiating interface 110 and a guided interface 112. The radiating and guided interfaces 110, 112 are at opposing ends (along the direction of RF wave propagation) of the waveguide device 100. The radiating interface 110 and the guided interface 112 may or may not share the same cross-section or geometry. In other words, the geometry or cross-section of the waveguide device 100 along the axis or direction of RF signal propagation may be uniform or may vary. It should be noted that, in some embodiments of device 100, the guided interface 112 may be ambiguous and, in some embodiments, the direction of RF signal propagation may be ambiguous. For example, in an embodiment, the waveguide device 100 may include multiple bends or paths in the waveguide structure (and the structure may be manufactured as a single piece) (e.g., Figure 7). In another embodiment, a feeding technique such as a coaxial feed point or probe may be used (e.g., at or near the guided interface) (e.g., Figure 8). In another embodiment, rather than propagating into a waveguide section, energy may be coupled to the waveguide section, such that there is no clear propagation vector (e.g., Figure 9).

[0064] In some embodiments, the radiating and guided interfaces 110, 112 may not be in line or configured such that they are at opposing ends along RF signal propagation direction) (see, for example, Figures 7-9).

[0065] The radiating interface 110 is a transmitting or receiving end (depending on the application). The radiating interface 110 is open to free space.

[0066] The guided interface 112 may be configured to couple to one or more other components of an antenna system. In an embodiment, the guided interface 112 couples the waveguide device 100 (and in particular the waveguide element 102) to a polarization circuit. In some embodiments, the waveguide device 100 may be mechanically mounted at or near the guided interface 112.

[0067] The waveguide device 100 may transmit RF signals or waves in transmit direction 114 through an interior cavity of the device 100. The waveguide device 100 may receive RF signals or waves in receive direction 116 through the interior cavity of the device 100.

[0068] The waveguide element 102 is shown in isolation in Figures 2A-2B. The waveguide element 102 includes six waveguide walls 201 (walls 201 -1 to 201 -6 in Figure 2B). Each wall 201 includes an outer or exterior face 202, an inner or interior face 204, a top surface 206 at a radiating interface (free space end) 208, a bottom surface 210 at a guided interface 212 (guided wave end). The inner faces 204 define a waveguide cavity 214 along which waves are propagated. The radiating interface 208 of the waveguide element 102 forms a waveguide element aperture 216 (or aperture plane). The waveguide element aperture 216 is denoted as a hashed line. It should be noted that when the waveguide element 102 is incorporated into the waveguide device 100, the crown 104 and ridges 108 move the radiating aperture of the waveguide device 100 beyond the waveguide element aperture 216 (which may also be referred to as a small waveguide aperture).

[0069] The waveguide element 102 has a hexagonal cross-section (as seen in Figure 2B). The hexagonal cross-section has equal dimensions along its length. In other embodiments, the waveguide element 102 may not be straight and / or may have a varying cross-section along the axis of RF signal propagation (e.g., smooth, stepped, profiled).

[0070] In other embodiments, the waveguide element 102 may have a crosssection of any other suitable shape. For example, the waveguide element 102 may have a square or rectangular cross-section, a circular cross-section, or the like. The shape may be a shape commonly used in array lattices. The cross-section may be polygonal. It will be understood by varying the cross-sectional shape of the waveguide element 102, the number of walls 201 will also vary. For example, where the waveguide element 102 has a circular cross-section, the waveguide element 102 will have a single wall and where the waveguide element 102 has a rectangular cross-section the waveguide element 102 will have four walls. The waveguide element 102 cross-section may vary along its length. In some embodiments, the internal (RF cavity) cross-section of the waveguide element 102 may differ from the external or outer cross-section of the waveguide element 102.

[0071] The waveguide element 102 is composed of a conductive material. In an embodiment, the waveguide element 102 is metallic.

[0072] Referring again to Figures 1A-1D, the crown 104 is disposed on the top surfaces 206 of the walls 201 of the waveguide element 102 at the radiating interface 208 such that the crown elements 106 extend beyond the aperture 216 of the waveguide element 102. The crown 104 may be integrally formed with the walls 201 of the waveguide element 102. The crown 104 may be one or more physically separate pieces from the walls 201 of the waveguide element 102 and then mounted or otherwise physically coupled to the top surface 206 of the waveguide element 102.

[0073] The crown 104 provides structural support for the ridge elements 108, aids in active matching, and breaks up leaky waves propagating across the surface of the array (when the waveguide device 100 is used as an array element in an array).

[0074] It should be noted that where the waveguide device 100 is used as a single waveguide probe (i.e. , not as part of an array), the crown 104 may act simply as a support structure for the ridge element 108 (ridge eases transition into free space) extending beyond the waveguide element aperture 216. This is because the leaky wave is not an issue in non-array applications.

[0075] When the waveguide device 100 is used in an array, the crown 104 creates an electromagnetic band gap structure that prevents leaky / surface waves from readilypropagating across the array lattice. The bandgap structure is a structure that stops waves of a certain frequency band such that those waves do not propagate. The bandgap structure may act as a filtering structure, allowing certain frequency bands to pass through while preventing other frequency bands from passing through. The bandgap structure may stop propagation of waves in a specific direction.

[0076] Further details of the crown 104 and crown elements 106 will now be described with reference to Figures 3A-3B.

[0077] The crown 104 includes six crown elements 106-1 to 106-6 (referred to generically as crown element 106 and collectively as crown elements 106). In other embodiments, the number of crown elements 106 may vary (e.g., two or more). The number of crown elements 106 may be the same as or different from the number of walls 201 of the waveguide element 102. By way of nonlimiting example, in an embodiment with a hexagonal waveguide element 102, the number of crown elements 106 may be six (i.e. , equal to the number of waveguide element walls 201) or four (fewer than the number of waveguide element walls 201 ). In another example, the number of crown elements 106 may be greater than the number of walls 201 (e.g. , two crown elements 106 per wall 201 ).

[0078] While all crown elements 106 of crown 104 are shown as identical, in some embodiments, crown elements 106 may be nonuniform such that not all crown elements 106 have identical dimensions.

[0079] As shown in Figure 3B, example crown element 106-1 includes outer face 302, inner face 304, side edges 306, 308, bottom edge 310, and tip 312. Bottom edge 310 is connected to top surface 206 of waveguide element 102 (through being either integrally formed with or mounted to top surface 206).

[0080] Crown element 106 may be any suitable shape. Crown element 106 may be triangular (e.g., as shown). Crown element 106 may be a half circle. Crown element 106 may be trapezoidal. The tip 312 of the crown element 106 may be pointed / sharp, rounded, or flat. The shape of the crown elements 106 is not particularly limited.

[0081] While embodiments in which all crown elements 106 have the same shape may be preferred, crown elements 106 do not need to have the same shape. Whethercrown elements 106 have the same shape may depend on the scan range of the antenna in which the waveguide device 100 is used. In general, asymmetry introduced by having crown elements 106 with different shapes may bias the direction (i.e., more sensitive in one direction).

[0082] In some embodiments, the crown elements 106 are disposed symmetrically around the top surface 206 of the waveguide element 102.

[0083] Where the waveguide element 102 has multiple faces (i.e., a non-circular cross-section), the bottom side 310 of the crown element 102 may run the entire width of the waveguide element face on which it is disposed or may be shorter than the waveguide element face (such as in device 100). Where the bottom side 310 is shorter than the width of the waveguide element face, the bottom side 310 may be centrally disposed along the width of the waveguide element face. In other embodiments, the bottom side 310 may not be centered. It can be seen in the embodiment of Figures 1A-D that the bottom side 310 of crown element 106 is shorter than the width of the waveguide element face and the crown element 106 is centrally positioned relative to the width of the waveguide element face.

[0084] In some embodiments, the crown elements 106 may be disposed about the waveguide element 102 such that they have rotational symmetry about the waveguide element 102.

[0085] Referring again to Figures 1A-1D, the ridge elements 108 will now be described in further detail. A representative ridge element 108 is shown in isolation in Figure 4.

[0086] The ridge elements 108 control the modal distribution of the RF fields inside the waveguide element 102. This may notably allow the propagation of the fundamental mode inside the waveguide element 102 that would otherwise be too narrow to do so by itself. By extending the above aperture, the ridges 108 ease the transition between conducted wave and free space.

[0087] The ridge element 108 is a protrusion of the waveguide element 102 interior wall. The ridge elements 108 ease the transition into free space (by extending beyond the aperture 216 of the waveguide 102).

[0088] The ridge elements 108 may be integrally formed with the walls 201 of waveguide element 102. The ridge elements 108 may be separate pieces from the waveguide element 102 that are physically coupled to the waveguide element 102.

[0089] The ridge elements 108 are composed of a conductive material. The ridge elements 108 may be metallic. The ridge elements 108 may be the same material as the waveguide element 102.

[0090] The waveguide device 100 includes six ridge elements 108 (i.e., one per waveguide element wall). In other embodiments, the number of ridge elements 108 may vary. The number of ridge elements 108 may match the number of crown elements 106, such as in waveguide device 100. In other embodiments, the number of ridge elements 108 may not match the number of crown elements 106 (e.g., fewer ridge elements 108 than crown elements 106). The number of ridge elements 108 may correspond to the number of waveguide element walls 201. The number of ridge elements 108 may be fewer or greater than the number of waveguide element walls 201. In some embodiments, there may be more than one ridge element 108 on a waveguide element wall 201. In some embodiments, the ridge element 108 may be disposed or otherwise located at the junction between two waveguide element walls 201 (i.e., in a corner).

[0091] The ridge elements 108 run along a portion of or the entire length of the waveguide element 102 from the guided interface 212 to the radiating interface 210 and extend beyond the waveguide aperture 216 at the radiating interface, onto the crown 104. The ridge elements 108 are supported by the crown elements 106 beyond the waveguide aperture 216. By extending the ridge elements 108 onto the crown 104, the return loss from the crown 104 is improved. How far up the crown elements 106 the ridge elements 108 go may vary. In an embodiment, the ridge element 108 may extend approximately halfway up the crown element 106.

[0092] The ridge elements 108 are disposed orthogonally to the waveguide element walls 201 and the inner face 302 of the crown elements 108. The ridge elements108 may be disposed about the waveguide element 102 such that they have rotationally symmetric geometry. The ridge elements 108 may or may not be symmetrical about the longitudinal axis of the waveguide element 102. The ridge element 108 may or may not be orthogonal to the element walls 201.

[0093] The ridge element 108 has a cross-section (along X-Y plane) and a profile (along Z-axis). The cross-section or profile of the ridge element 108 may change along its length or be constant. The cross-section of the ridge element 108 may be rectangular. The cross-section of the ridge element 108 may be curved, stepped, or vary along its length. The profile of the ridge element 108 may change along its length or be constant. The profile of the ridge element 108 may be curved, stepped, or vary along its length.

[0094] The ridge elements 108 may be centrally disposed on the crown elements 106. Such a configuration is shown in Figures 1A-1D. In other embodiments, the ridge elements 108 may not be centrally disposed on the crown elements 106.

[0095] In some embodiments, the crown elements 106 and the ridge elements 108 may flare beyond the exterior walls 202 of the waveguide element 102. Such a configuration may be used, for example, in a single waveguide device implementation. Such a configuration may not be appropriate for an array application (for example, because of the relative positioning of the array elements).

[0096] Referring now to Figure 4, an example ridge element 108 is shown in isolation.

[0097] The ridge element 108 includes a first side edge 402, a second side edge 404, a top end 406, and a bottom end 408. The top end 406 corresponds to the radiating interface 110 of the waveguide device 100 and the bottom end 408 corresponds to the guided interface 112 of the waveguide device 100.

[0098] The first side edge 402 is disposed towards the inner face 204 of the waveguide element wall 201. The first side edge 402 may be integrally formed with the waveguide element wall 201.

[0099] The first side edge 402 follows the profile of the inner face 204 of the waveguide element wall 201 on which the ridge element 108 is disposed. The first sideedge 402 may be straight or curved. The first side edge 402 is generally orthogonal to the waveguide element wall 201 (such that the ridge element 108 protrudes orthogonally from the waveguide element into the cavity 214).

[0100] The second side edge 404 may be straight or curved. The profile of the second side edge 404 may be the same along the entire length of the second side edge 404 or may vary along the length of the second side edge 404. For example, in some cases, the second side edge 404 may have a curved portion and a straight portion. As an example, an upper portion 410 of second side edge 404 may be curved and a lower portion 412 of second side edge 404 may be straight, or vice versa.

[0101] It should be noted that, in variations, the ridge elements 108 may or may not all have the same shape and dimensions (device 100 has ridge elements 108 with identical shape and dimensions).

[0102] The ridges 108 control the impedance change to free space in conjunction with the crown 104. The crown 104 creates an electromagnetic band gap structure that prevents leaky or surface waves from readily propagating across the array lattice, causing scan blindness. It should be noted that the crown 104 has some influence on interelement coupling, which is something that can affect the active match significantly, with an increasing impact as the beam is steered away from nadir (or other (0,0) position of the antenna steering).

[0103] As previously noted, in space applications, dielectrics are avoided where possible to avoid outgassing risks and corona. The waveguide device 100 of the present disclosure provides an alternative impedance matching approach to achieve a good match. The use of a crown 104 alone (without ridges 108) may degrade the match of the initial waveguide element 102. Having the ridges 108 extend beyond the initial aperture 216 of the waveguide element 102 and onto the crown 104, the performance (of an array of waveguide devices 100) at nadir at low frequencies improved and good performance was achieved at high scan angles and high frequencies.

[0104] Simulations using the waveguide device 100 have demonstrated improved overall transmission of the waveguide element 102, as well as removal of the surface wave.

[0105] Referring now to Figures 6-9, shown therein waveguide devices 600a, 600b, 600c, and 600d, respectively, according to embodiments. The waveguide devices 600a-d are variants of the waveguide device 100 of Figures 1A-1D.

[0106] Waveguide devices 600a-600d each include the following components: waveguide wall 602 (of a waveguide element, such as waveguide element 102 of Figure 1A), crown 604, ridge 606, waveguide element aperture 608 (i.e., the aperture in waveguide element wall 602), guided interface 610, guided wave propagation 614, and radiated wave propagation 612. In each embodiment of the device 600a-600d, crown 604 and ridge 606 extend beyond the waveguide element aperture 608 into free space. This may effectively move the radiation aperture beyond the aperture 608 of the waveguide element. In some embodiments, the device 600a-600d may be additively manufactured as one part. In some cases, the device 600a-600d may be mounted mechanically at or near the guided interface 610.

[0107] Waveguide device 600a is a straight waveguide.

[0108] Waveguide device 600b is a bent waveguide. The profile of the waveguide device 600b (and thus the waveguide wall 602 and ridge 606) is stepped. The direction of guided wave propagation 614 at the guided interface 610 is perpendicular to the direction of guided wave propagation 614 approaching the radiation aperture 608 and to the direction of radiated wave propagation 612.

[0109] Waveguide device 600c is a probe-fed waveguide that further includes coaxial line 616. The probe (not shown) excites mode(s) in the waveguide at 620. Ridge 606 does not extend all the way to the bottom waveguide wall 602 at one section to accommodate the coaxial line 616. It will be understood that the probe is simply one example of a feed technique and that, in other embodiments, other feed techniques may be used.

[0110] Waveguide device 600d is an excited slot waveguide. Unlike devices 600a-c, guided interface 610 no longer has a clearly defined propagation direction. Waveguide device 600d further includes electrically small slot 622.

[0111] It is also worth noting in waveguide device 600d that ridge element 606-1 may include a ridge portion that extends or protrudes beyond the waveguide wall 602 into the waveguide interior cavity. The protruding ridge portion may support better wave coupling. Figure 9 illustrates energy coupling at 624. It should be noted that while Figure 9 illustrates a single aperture 608, in some embodiments, waveguide device 600d may include a plurality of apertures 608, each with associated crown 604 and ridge elements 606, disposed along the same waveguide wall 602 at some distance apart (e.g., along the direction of guide wave propagation 614). Each aperture 608 would have energy 624 coupled thereto. Where waveguide device 600d includes a plurality of apertures 608, the apertures 608, and in particular the configuration of the crown 604 and ridges 606, may be identical to one another or may vary. Line 626 in Figure 9 denotes an arbitrary cut of device 600d. Accordingly, in variations, waveguide walls 602 may end at line 626 (e.g., by a third waveguide wall perpendicular to the walls 602) or may extend beyond line 626.

[0112] While the above description provides examples of one or more apparatus, methods, or systems, it will be appreciated that other apparatus, methods, or systems may be within the scope of the claims as interpreted by one of skill in the art.

Claims

Claims:

1. A waveguide device for transmitting or receiving radio frequency (RF) signals, the waveguide device comprising:a waveguide element including a waveguide element aperture and a guided wave interface;a crown comprising one or more crown elements disposed on a surface of the waveguide element at a radiated wave interface of the waveguide device such that the crown elements extend beyond the waveguide element aperture; andone or more ridge elements disposed on an interior surface of the waveguide element and running along a portion of or the entire length of the waveguide element from the guided wave interface to the waveguide element, the ridge elements supported by the crown beyond the waveguide element aperture.

2. The waveguide device of claim 1 , wherein the crown and the one or more ridges form a radiating aperture of the waveguide device beyond the waveguide element aperture.

3. The waveguide device of claim 1, wherein the waveguide element includes a plurality of waveguide element walls and at least one of the one or more ridge elements is disposed at a junction between two adjacent waveguide element walls.

4. The waveguide device of claim 1 , wherein the one or more ridge elements includes a plurality of ridge elements with identical shape and size.

5. The waveguide device of claim 1 , wherein the one or more ridge elements include at least two ridge elements with different shapes or different dimensions.

6. The waveguide device of claim 1, wherein the waveguide element includes a plurality of waveguide element walls and at least one of the plurality of waveguide element walls has at least two of the one or more ridge elements disposed thereon.

7. The waveguide device of claim 1 , wherein the number of crown elements is equal to the number of ridge elements.

8. The waveguide device of claim 7, wherein the one or more ridge elements are centered on the one or more crown elements.

9. The waveguide device of claim 1, wherein the waveguide element includes a plurality of waveguide element walls and each of the one or more crown elements is centered on a respective waveguide element wall.

10. The waveguide device of claim 1 , wherein the waveguide element has a hexagonal cross-section with six walls.

11. The waveguide device of claim 1, wherein the waveguide element has a rectangular or square cross-section.

12. The waveguide device of claim 1, wherein the waveguide element has a circular cross-section.

13. The waveguide device of claim 1, wherein the waveguide element has an inner cross-section and an outer cross-section that are different.

14. The waveguide device of claim 10, comprising six crown elements and six ridge elements, wherein each wall of the waveguide element has one crown element and one ridge element disposed thereon.

15. The waveguide device of claim 1 , wherein each of the one or more ridge elements includes a first side edge integral with an inner wall of the waveguide element anda second side edge facing an inner cavity formed by the inner wall of the waveguide element.

16. The waveguide device of claim 15, wherein the second side edge is curved.

17. The waveguide device of claim 15, wherein a profile of the second side edge is the same along the entire length of the second side edge.

18. The waveguide device of claim 15, wherein a profile of the second side edge varies along the length of the second side edge.

19. The waveguide device of claim 18, wherein the second side edge has a straight portion and a curved portion.

20. The waveguide device of claim 18, wherein the profile of the second side edge is stepped.

21. The waveguide device of claim 1 , wherein the waveguide element includes one or more walls defining an inner cavity of the waveguide element, each of the one or more ridge elements is disposed on at least one of the one or more walls, and each of the one or more ridge elements is orthogonal to the wall on which the respective ridge element is disposed.

22. The waveguide device of claim 1 , wherein the waveguide element includes one or more walls defining an inner cavity of the waveguide element, each of the one or more ridge elements is disposed on at least one of the one or more walls, and each of the one or more ridge elements is not orthogonal to the wall on which the respective ridge element is disposed.

23. The waveguide device of claim 1 , wherein the waveguide element includes one or more walls defining an inner cavity of the waveguide element, and wherein the number of crown elements is greater than the number of walls.

24. The waveguide device of claim 1 , wherein the one or more crown elements is a plurality of crown elements that are identical in shape and size.

25. The waveguide device of claim 1 , wherein the one or more crown elements are triangular or trapezoidal.

26. The waveguide device of claim 1 , wherein the one or more crown elements each include a pointed tip.

27. The waveguide device of claim 1 , wherein the one or more crown elements each include a rounded tip.

28. The waveguide device of claim 1 , wherein the waveguide element includes one or more walls defining an inner cavity of the waveguide element, and wherein the number of ridge elements is greater than the number of walls.

29. An array antenna comprising a plurality of the waveguide devices of claim 1 arranged in an array.

30. A waveguide probe comprising the waveguide device of claim 1.

31. The waveguide device of claim 1 , wherein the waveguide device is fed by a coaxial line or probe that excites a mode in the waveguide element.

32. The waveguide device of claim 1 , wherein the guided wave interface is a guided wave feed point, and wherein a guided wave at the guided wave feed point is orthogonal to a radiated wave at the radiated wave interface.

33. The waveguide device of claim 1 , wherein the waveguide element has a stepped profile, and wherein the one or more ridges have a stepped profile that follows the stepped profile of the waveguide element.

34. The waveguide device of claim 1 , wherein the waveguide element uses energy coupling.

35. The waveguide device of claim 34, wherein at least one of the one or more ridge elements protrudes beyond a wall of the waveguide element into an interior of the waveguide element at the radiated wave interface to support wave coupling.

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