Waveguide to stripline transition

Abstract

An antenna subsystem may include a waveguide having an opening. The antenna subsystem may include an antenna subassembly. The antenna subsystem may include a multi-layer substrate arranged between the waveguide and the antenna subassembly, the multi-layer substrate including a waveguide transition. The transition may include an aperture layer including an annular aperture. The aperture layer may be coupled to the opening of the waveguide. The transition may include a ground reference layer. The transition may include a transmission line layer between the aperture layer and the ground reference layer and may include an embedded transmission line that extends into a cavity and the ground reference layer may provide a ground reference for the embedded transmission line. The subsystem may include an interconnect that couples the embedded transmission line to the antenna subassembly and that passes through the ground reference layer.

Description

WAVEGUIDE TO STRIPLINE TRANSITIONBACKGROUND

[0001] The following relates generally to communications, including waveguide to stripline transition.

[0002] In radio frequency (RF) and microwave systems such as satellite or other wireless communication systems, effective transmission of electromagnetic signals requires transitions between different types of transmission mediums, such as free space, waveguides, and printed circuit board (PCB) components (e.g., striplines). Waveguides serve as a highly efficient medium for guiding electromagnetic waves, especially at higher frequencies. They are typically used in applications demanding low loss and high power handling capabilities. Striplines are planar transmission lines constructed within PCBs in which the stripline is separated from ground reference planes by the PCB dielectric, and thus has an impedance that is determined by the PCB structure and dielectric. Transitions between waveguide and stripline transmission mediums may provide challenges in communication systems because of signal reflection or impedance mismatch.SUMMARY

[0003] The described techniques relate to an improved waveguide to stripline transition.

[0004] An antenna subsystem is described. The antenna subsystem may include a waveguide having an opening, an antenna subassembly comprising one or more antenna elements (e.g., an antenna array), the one or more antenna elements having a footprint within an antenna element layer of the antenna subassembly, a multi-layer substrate arranged between the waveguide and the antenna subassembly, the multi-layer substrate comprising a waveguide transition that is disposed within the footprint and that comprises: an aperture layer of the multi-layer substrate, wherein the aperture layer comprises an annular aperture that is disposed within a cross-section of the opening of the waveguide, and wherein the aperture layer is coupled to the opening of the waveguide; a ground reference layer of the multi-layer substrate; a transmission line layer between the aperture layer and the ground reference layer, the transmission line layer comprising an embedded transmission line that extends into a cavity comprising a cavity termination surface that is comprised within the transmission line layer, wherein the ground reference layer provides a first ground reference for the embedded transmission line; and an interconnect that couples the embeddedtransmission line to the antenna subassembly and that passes through the ground reference layer. Some examples of the antenna subsystems described herein may include a footprint of the waveguide transition may be located within the footprint of the one or more antenna elements. Some examples of the antenna subsystems described herein may include the ground reference layer of the multi-layer substrate provides a ground reference for the one or more antenna elements.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 shows an example of a waveguide transition with a back short.

[0006] FIG. 2 shows an example of a transition that supports waveguide to stripline transition in accordance with aspects of the present disclosure.DETAILED DESCRIPTION

[0007] In some wireless communications systems, waveguides may be used to guide radio frequency (RF) waves used for wireless communications between entities of the system. For example, in a satellite communications system mobile terminals, satellites, ground stations, gateways, or other elements may employ waveguides. In an antenna subsystem of a satellite, the waveguide may guide the RF waves (e.g., to be carried in a direction) to be received by other structures or elements, such as a transmission line (e.g., a stripline), which may in turn be connected to other structures or elements of the antenna subsystem. To facilitate the use of such elements, it may be desirable to construct a transition from the waveguide to the stripline or to other structures or elements of the antenna subsystem (e.g., to an antenna element of an antenna subassembly). However, some approaches to constructing a transition employ the use of a back short, which may extend beyond a portion of the multilayer substrate (e.g., one or more layers of the multi-layer substrate) used to construct the transition and that provide connectivity between different elements of the antenna subsystem. Such an extension beyond the portion of the multi-layer substrate may occupy additional physical space that may not allow for placement of other elements of the antenna subsystem in proximity to the multi-layer substrate, such as an antenna subassembly including one or more antenna elements that may be used to interact with RF waves.

[0008] In some examples, a waveguide to stripline transition may be employed to transition between the waveguide and the stripline (e.g., and ultimately to one or more antenna elements or other elements of an antenna subsystem) without involving the use of aback short that occupies additional physical space, and thus without the increased physical size and increased distances associated with the back short. Such a transition may include the use of a multi-layer substrate arranged between an antenna subassembly and a waveguide. The multi-layer substrate may include an aperture layer that includes an annular aperture, a ground reference layer, and a transmission line layer between the ground reference layer and the aperture layer. The transmission line layer may include an embedded transmission line (e.g., a stripline) extending into a cavity, the cavity including a cavity termination surface (e.g., optionally within the transmission line layer). In some examples, the transmission line layer may include a shorting plane, which may eliminate the use of the back short present in other approaches. In some examples, the transmission line may couple to a maximum current point introduced by the shorting plane. The ground reference layer may serve as a ground reference for the embedded transmission line. The transmission line may be coupled to an interconnect that may couple transmission line to the antenna subassembly and the interconnect may pass through the ground reference layer.

[0009] As such, the transition may offer a functional transition between the waveguide and the transmission line (e.g., the stripline) without the use of a back short, reducing physical space considerations and allowing for more flexible location of elements (e.g., an antenna subassembly including one or more antenna elements to which the transmission line is coupled). Further, overall complexity of manufacturing the transition or of an antenna subassembly may be reduced, as there is no need to modify a housing or other elements to accommodate the physical space occupied by the back short. Further, such approaches may offer increased performance, due to lowered insertion loss and large return loss frequency bandwidth associated with the waveguide to transmission line transition (e.g., such as may be used in RF systems, such as W Band systems).

[0010] Aspects of other approaches to waveguide to stripline transitions are initially described. Aspects of the disclosure are then illustrated by and described with reference to an apparatus diagram.

[0011] FIG. 1 shows an example of a waveguide transition 100 with a back short. The waveguide transition 100 may include multiple layers, including multiple metal layers 112 and dielectric layers 120. The metal layers 112 may be interconnected to one another or to other elements of a device incorporating the waveguide transition 100 via one or more vias 1 18.

[0012] The waveguide transition 100 may include the back short 116. The back short 116 may be a portion of the waveguide 110 that is shorted (e.g., connected to a ground reference). The use of the back short 116 may be sized to be approximately 1 / 4 of a wavelength of RF waves for which the waveguide transition 100 may be employed. The use of the back short 116 may further allow for a connection to a stripline 114 that may be connected to one or more other elements of the waveguide transition 100 or other elements of a device incorporating the waveguide transition 100. For example, stripline 114 may be connected to antenna element 125 through a via 1 18 or a sub-assembly connector 1 19 (e.g., a PCB connector, pin, solder ball). The use of the back short 116 may allow a higher voltage or current to be produced in the plane of the stripline 114 that may increase the signal resulting from the directed RF waves. The ground reference 113 for the stripline may be planar ground reference features in additional layers of the substrate 126 (e.g., above and below the stripline 114).

[0013] However, due to the design, the back short 116 extends into the region 122. By extending into the region 122, other components cannot be placed within the region 122. For example, the antenna subassembly 124 or other elements cannot be placed in close proximity to the substrate 126, as the back short 116 extends beyond the substrate 126 into the region 122. In some cases (e.g., in a satellite), physical space (e.g., volume) may be in short supply, and moving components to accommodate the back short 116 may result in excess volume or weight, which may not be desirable in a satellite system or in other contexts.

[0014] FIG. 2 shows an example of an antenna subsystem 200 in accordance with examples as described herein. The antenna subsystem 200 may include a multilayer substrate 212 and an antenna subassembly 214. Although illustrated in FIG. 2 as separate substrates, the multiplayer substrate 212 and the antenna subassembly 214 may be a single substrate.

[0015] The multilayer substrate 212 may include multiple metal layers (e.g., the ground reference layer 218, the intermediate layer 224, the transmission line layer 226, the cavity layer 232, the aperture layer 234, the additional layers 240, or any combination thereof) and multiple dielectric layers. For clarity, the dielectric layers are not depicted in FIG. 2, but it is to be understood that one or more dielectric layers may be inserted at any point between any of the metal layers or other layers (e.g., in a similar manner as the dielectric layers 120). Though some layers are shown and discussed, multiple instances of such layers may be used and other layers may also be present in the multilayer substrate 212, the antenna subassembly 214, one or more other elements of the antenna subsystem 200, or any combination thereof.The antenna subsystem 200 may include a waveguide transition 205 between a waveguide 210 and a transmission line 230. In some examples, the waveguide transition 205 between the waveguide 210 and the transmission line 230 (which may be a stripline) may be contained entirely within the multilayer substrate 212. For example, the transmission line 230 may be embedded within the multilayer substrate 212, and the waveguide transition 205 may not include a back short of the waveguide 210.

[0016] Similar to the multilayer substrate 212, the antenna subassembly 214 may include one or more metal layers and one or more dielectric layers. Further, the antenna subassembly 214 may include one or more antenna elements 216, circuitry for controlling the antenna elements 216, one or more beamforming networks, one or more other elements, or any combination thereof. The antenna elements 216 may be part of an antenna array. In some cases, the antenna subassembly 214 may include a beamforming network between a connection to the transmission line 230 and the antenna elements 216.

[0017] The antenna elements 216 may define a footprint 215 in an antenna element layer 217. In some cases, the antenna elements 216 may take up a majority or substantially all of the footprint 215 (e.g., may be closely spaced). In addition, the antenna subassembly 214 may include additional antenna subassembly layers 219, which may include additional components, at least some of which may be within the footprint 215 such as on a back side of a layer that is adjacent to the multilayer substrate 212 (e.g., such that they would conflict with a back short present in multilayer substrate 212).

[0018] The transmission line 230 may feed the antenna elements 216 directly, or via one or more components (e.g., circuits such as amplifiers, phase shifters). In some examples, each transmission line 230 may be associated with a respective antenna element 216. In some examples, multiple transmission lines 230 may be associated with a single antenna element 216 or a single transmission line 230 may be associated with multiple antenna elements 216.

[0019] The waveguide 210 may serve to direct RF waves towards other elements of the antenna subsystem 200 and may include an opening 211 that may be coupled with the transition of the multilayer substrate 212. The waveguide 210 may terminate at the interface between the waveguide 210 and the multilayer substrate. The waveguide 210 may serve to direct RF waves toward the aperture 236 and the transmission line 230.

[0020] The additional layers 240 may provide connections to portions of the multilayer substrate 212 or to other elements of a device that includes the antenna subsystem 200. Forexample, in some cases, the additional layers 240 may act as a ground reference for one or more elements of the antenna subsystem 200. In some examples, the additional layers 240 may be referred to as passthrough layers (e.g., the RF waves pass through such layers and the layers have little or no interactions with the RF waves beyond providing a small pathway for the RF waves to arrive at the aperture layer 234 or other layers of the multilayer substrate 212. For example, the additional layers 240 may include openings that correspond with a cross-section of the opening 211 of the waveguide 210. The cross-section of the opening 211 of the waveguide 210 may also he considered a footprint of the waveguide transition 205, and may be within a footprint 215 of the antenna elements 216. In some examples, the additional layers 240 may carry other signaling in the multilayer substrate 212 (e.g., outside of the waveguide transition area).

[0021] The aperture layer 234 may include an aperture 236, which may be an annular aperture such that the aperture layer 234 includes a portion that is decoupled from other elements (e.g., floating). For example, the aperture layer 234 may include an annular aperture through which RF waves may pass. The aperture 236 may be located in a shorted face of the waveguide 210. For example, the aperture 236 may be located within a footprint or boundary of the waveguide 210. In some examples, the aperture layer 234 may include a shorted portion which may be coupled with the ground reference layer 218 through one or more ground vias 238.

[0022] The cavity layer 232 may define at least a portion of a boundary of a cavity into which the transmission line 230 may extend. Further, the cavity layer 232 may act as a ground reference for the transmission line 230 (e.g., where a footprint of the transmission line 230 overlaps with a footprint of the cavity layer 232). The cavity layer 232 may include a cavity with a footprint (e.g., cross-section) that encompasses an aperture footprint (e.g., crosssection) of the annular aperture of the aperture layer 234.

[0023] The transmission line layer 226 may include a shorted portion and the transmission line 230. The transmission line 230 may be a stripline element. For example, the transmission line 230 may be an intermediate layer of the multilayer substrate 212 and may have ground reference planes above and below the stripline for substantially all of the length of the stripline within the multilayer substrate 212. The transmission line 230 may interact with the RF waves and may produce a signal along the transmission line 230 that may be carried through the transmission line 230, through the interconnect via 228, to the antenna subassembly 214 where it may connect to one or more elements thereof (e.g., an antennaelements 216, a component of the antenna subassembly 214). For example, the interconnect via 228 may pass through one or more layers of the multilayer substrate (e.g., the intermediate layer 224, the ground reference layer 218) and may be coupled with one or more layers of the antenna subsystem 214 (e.g., the antenna element layer 217, other antenna subassembly layers 219). In some cases, the interconnect via 228 passes through some layers of the antenna subassembly 214 (e.g., passes through one or more layers, coupled to one or more different layers). In some examples, shorted portions of the transmission line layer 226 may be coupled with the ground reference layer 218 through one or more ground vias 238.

[0024] The intermediate layer 224 may be a layer between the ground reference layer 218 and the transmission line layer 226. In various examples, a single intermediate layer 224 may be present or multiple intermediate layers 224 may be present. Additionally, or alternatively, a single intermediate layer 224 may be present or multiple intermediate layers 224 may be present at any position in the multilayer substrate 212, the antenna subassembly 214, or both. The intermediate layer 224 may include an opening 220 and a portion of the transmission line 230 may be located within a footprint of the opening 220 (e.g., so that a portion of the transmission line 230 may reference the ground reference layer 218 as a ground reference). In some examples, the opening 220 may form a portion of the cavity. Further, the intermediate layer 224 may act as a ground reference for portions of the transmission line 230 (e.g., where a footprint of the transmission line 230 overlaps with a footprint of the intermediate layer 224).

[0025] The ground reference layer 218 may serve as a ground reference for the transmission line 230, one or more other elements of the multilayer substrate 212, the antenna subassembly 214, or both. In some examples, the ground reference layer 218 (or another layer described herein, such as the intermediate layer 224) may include a cavity termination surface that may define a portion of the cavity into which the transmission line 230 may extend. In some examples, one or more layers coupled with the ground reference layer 218 may be coupled through one or more ground vias 238, which may also be referred to as mode suppression pins or mode suppression vias.

[0026] In some examples, the transmission line 230 may include a tapered portion 242. The tapered portion 242 may transition from a portion of the transmission line 230 that extends into the cavity to the interconnect via 228. In some examples, the portion of the transmission line 230 that extends into the cavity may reference the ground reference layer 218 as a ground reference. However, in some examples, the portion of the transmission line230 that is between the tapered portion 242 and the interconnect via 228 may instead reference the intermediate layer 224, the cavity layer 232, one or more other layers, or any combination thereof, as a ground reference layer (e.g., because there is no cutout in the corresponding portions of the intermediate layer 224, the cavity layer 232, one or more other layers, or any combination thereof.

[0027] In some cases, the opening 220 of the intermediate layer 224, and the cavity of the cavity layer 232 extend outside the cross-section of the opening of the waveguide 210 (e.g., before tapering at a portion corresponding to the tapered portion 242 of the transmission line 230. Thus, the transmission line 230 may have a first portion that extends into the cavity defined by the opening of the waveguide 210, a tapered portion 242, and a second portion that is in between the tapered portion 242 and the interconnect via 228. The first portion may be proximate to the waveguide transition 205 (e.g., may be partially within the footprint of the opening 21 1 of the waveguide 210) and have a first (e.g., larger) width and the second portion may be distal to the waveguide transition 205 (relative to the first portion) and have a second (e.g., smaller) width. The first width of the transmission line 230 at the first portion may be selected based on the dimensions of the waveguide 210 and RF frequency of signals for the waveguide transition. The second width of the transmission line 230 at the second portion may be selected based on a desired stripline impedance of the transmission line 230 and a dimension of the dielectric layers of the multilayer substrate 212. Ground reference for the transmission line 230 may be provided by a first set of layers of the multilayer substrate 212 (e.g., the ground reference layer 218, the aperture layer 234) for the first portion and by a second set of layers (e.g., the intermediate layer 224, the cavity layer 232) for the second portion.

[0028] In some cases, the ground reference layer 218 may serve as a ground reference for one or more of the antenna elements 216. Additionally or alternatively, one or more antenna subsystem layers 217 may serve as the ground reference for one or more of the antenna elements 216.

[0029] It should be noted that these methods describe examples of implementations, and that the operations and the steps may be rearranged or otherwise modified such that other implementations are possible. In some examples, aspects from two or more of the methods may be combined. For example, aspects of each of the methods may include steps or aspects of the other methods, or other steps or techniques described herein.

[0030] Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0031] As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of’) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an exemplary step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.”

[0032] In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label.

[0033] The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “exemplary” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

[0034] The description herein is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variationswithout departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

CLAIMSWhat is claimed is:

1. An antenna subsystem, comprising: a waveguide having an opening; an antenna subassembly comprising one or more antenna elements, the one or more antenna elements having a footprint within an antenna element layer of the antenna subassembly; a multi-layer substrate arranged between the waveguide and the antenna subassembly, the multi-layer substrate comprising a waveguide transition that is disposed within the footprint and that comprises: an aperture layer of the multi-layer substrate, wherein the aperture layer comprises an annular aperture that is disposed within a crosssection of the opening of the waveguide, and wherein the aperture layer is coupled to the opening of the waveguide, a ground reference layer of the multi-layer substrate, and a transmission line layer between the aperture layer and the ground reference layer, the transmission line layer comprising an embedded transmission line that extends into a cavity comprising a cavity termination surface that is comprised within the transmission line layer, wherein the ground reference layer provides a first ground reference for the embedded transmission line; and an interconnect that couples the embedded transmission line to the antenna subassembly and that passes through the ground reference layer.

2. The antenna subsystem of claim 1 , wherein a footprint of the waveguide transition is located within the footprint of the one or more antenna elements.

3. The antenna subsystem of claim 1 , wherein the ground reference layer of the multi-layer substrate provides a ground reference for the one or more antenna elements.

4. The antenna subsystem of claim 1 , wherein the ground reference layer of the multi-layer substrate is separated from the transmission line layer of the multi-layer substrate by one or more intermediate layers of the multi-layer substrate.

5. The antenna subsystem of claim 4, wherein the one or more intermediate layers comprise an opening that corresponds to the embedded transmission line.

6. The antenna subsystem of claim 1 , wherein the waveguide transition further comprises a cavity layer of the multi-layer substrate disposed between the transmission line layer of the multi-layer substrate and the aperture layer of the multi-layer substrate, the cavity layer of the multi-layer substrate defining a cavity footprint of the cavity, the cavity footprint encompassing an aperture footprint of the annular aperture.

7. The antenna subsystem of claim 1, wherein: the one or more antenna elements form an antenna array; and the multi-layer substrate comprises a beamforming network associated with the antenna array, the beamforming network disposed between the transmission line layer of the multi-layer substrate and the antenna array.

8. The antenna subsystem of claim 1 , wherein: at a first location proximate to the waveguide transition, the ground reference layer of the multi-layer substrate provides the first ground reference for the embedded transmission line; and at the first location, the aperture layer provides a second ground reference for the embedded transmission line.

9. The antenna subsystem of claim 8, wherein: at a second location distal to the waveguide transition, a first intermediate layer between the transmission line layer and the ground reference layer provides the first ground reference for the embedded transmission line; and at the second location, a second intermediate layer between the transmission line layer and the aperture layer provides the second ground reference for the embedded transmission line.

10. The antenna subsystem of claim 9, wherein a first width of the embedded transmission line at the first location is greater than a second width of the embedded transmission line at the second location.

11. The antenna subsystem of claim 1 , wherein the transmission line layer of the multi-layer substrate further comprises: a first grounded portion that is decoupled from the embedded transmission line; wherein the first grounded portion is coupled to the ground reference layer of the multi-layer substrate with one or more vias.

12. The antenna subsystem of claim 1, wherein: the aperture layer of the multi-layer substrate comprises a grounded portion that encompasses the annular aperture, and the aperture layer of the multi-layer substrate is coupled to the ground reference layer of the multi-layer substrate with one or more vias.

13. The antenna subsystem of claim 1 , wherein the multi-layer substrate further comprises a plurality of dielectric layers that at least partially insulate the aperture layer of the multi-layer substrate, the ground reference layer of the multilayer substrate, and the transmission line layer of the multi-layer substrate from one another.

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