Rotational transmission system using waveguides

Abstract

A coupler provides a high-speed data link between rotatable parts comprising a circular gap surrounding a hollow cylindrical volume and at least two antennas. The circular gap is made of electrically conductive material and comprises a first ring, a second ring rotatable relative to the first ring, and two side walls on both sides of the rings. A first antenna is mechanically coupled to the first ring and a second antenna is mechanically coupled to the second ring. The antennas are configured for microwave signal connection between them based on multiple reflections at the rings.

Description

Technical Field

[0001] The present invention relates to a rotary transmission system for providing a non-contact, high-speed data link between rotatable devices, which can be particularly used in computed tomography scanners. Background Technology

[0002] Non-contact data links can be used to couple rotatable devices (such as the rotatable portion of a computed tomography (CT) scanner gantry) to stationary parts. Data rates are in the range of 1 Gbit / s or even greater than 10 Gbit / s. Such data links can also be referred to as rotary joints or slip rings.

[0003] Because CT scanners have large inner apertures to accommodate patients to be scanned, the rotary joints used therein must have large diameters, typically in the range of 1-1.5 m. US5,646,962 discloses such a non-contact rotary joint based on a stripline for guiding signals around a circular body and a capacitive pickup movable thereto for receiving said signals.

[0004] Another method, as disclosed in EP 0 093 468, uses a waveguide for signal transmission. A stationary waveguide comprising a circular, conductive, hollow body has a fixed receiving antenna. Furthermore, a rotatable transmitting antenna is movable in a radial slot within the body to couple signals into the interior of the waveguide. These signals travel along the waveguide until they reach the receiving antenna.

[0005] The problem is the relatively small relative bandwidth of the waveguide, which limits the available data rate. Furthermore, the radial slots in the waveguide must be relatively narrow to avoid waveguide degradation. The transmission antenna must fit into this slot and therefore can only be a small pin. Such an antenna is limited in terms of bandwidth and efficiency. Summary of the Invention

[0006] The problem this invention aims to solve is to provide improved high-speed coupling between rotatable parts.

[0007] The solution to this problem is described in the independent claims. The dependent claims relate to further improvements to the invention.

[0008] Also known as a high-speed data link rotary joint, a rotary joint for a high-speed data link including rotatable parts comprises a first ring and a second ring coaxially arranged around a central axis. The first ring has a first diameter, and the second ring has a second diameter larger than the first diameter. The first and second rings comprise at least partially conductive materials. At least one ring may be metallic, such as copper, aluminum, or steel. At least one ring may also have a conductive surface oriented toward the other ring. The surface and / or the rings themselves may also comprise resistive and / or absorbing and / or attenuating materials.

[0009] The first and second rings have a circular gap and can form a circular channel. Furthermore, the first and second rings can be axially aligned. Essentially, either of the rings can be stationary and / or rotatable. Therefore, both rings can be stationary, or both rings can be rotatable. Additionally, one ring can be stationary while the other is rotatable.

[0010] The circular channel may further include at least one or two sidewalls. A first sidewall is axially positioned on one side of the ring, while a second sidewall is axially positioned on the other side or opposite side of the ring. The first ring, the second ring, the first sidewall, and the second sidewall form a closed circular channel, which may have a rectangular or square cross-section. Essentially, any one of the sidewalls may be stationary or rotatable.

[0011] The sidewalls are not essential for transmission functionality, but they can help decouple signals transmitted from the environment or adjacent channels by using reflective or absorbing sidewalls. Furthermore, the sidewalls can include combinations of absorbing materials that can be mounted onto the reflective surface. Therefore, standard wireless networks such as IEEE 802.11 can be used without interfering with external wireless network installations for other purposes.

[0012] For transmitting or coupling signals, a first antenna and a second antenna rotatable relative to the first antenna are provided. Because the two antennas are rotatable relative to each other, either antenna can be stationary while the other is rotatable. The first and second antennas can rotate independently of either of the rings.

[0013] For RF signal coupling, the first antenna can be pointed into the circular gap in a first direction and at a first beam angle (also referred to herein as the first angle). The second antenna can be pointed into the circular gap in a second direction opposite to the first direction and at a second beam angle (also referred to herein as the second angle). The first and second angles are defined radially relative to the central axis. They can have absolute values ​​ranging from 0° to 90° or from 1° to 89°. This allows microwave signals to be transmitted between the first and second antennas if one of the antennas radiates a signal into the gap and the other antenna receives the signal from the gap. The first and second loops can reflect microwave signals, allowing the microwave signals to propagate through the loops.

[0014] The first angle and the second angle can be fixed values ​​that do not change with rotation and are therefore constant with rotation. Furthermore, the first antenna and the second antenna can have a radiation pattern that remains constant with rotation.

[0015] In one embodiment, the first antenna may be mechanically coupled to the first ring, and the second antenna may be mechanically coupled to the second ring. The first antenna and the second antenna point into the space between the first ring and the second ring.

[0016] In one embodiment, the absolute value of the first angle can be greater than the 3dB (half-power) beamwidth of the first antenna, and the absolute value of the second angle can be greater than the 3dB (half-power) beamwidth of the second antenna. Simulation series and experimental evidence at specific data points have revealed that, under these conditions, maximum bandwidth with acceptable signal distortion can be achieved. Therefore, dispersion caused by multiple paths can be kept at a level that allows for channel equalization using equalization techniques known from, for example, the IEEE 802.11 standard.

[0017] The ring and / or sidewalls may include electromagnetic reflective materials, such as conductive materials, or may have conductive surfaces, or they may include dielectric materials with a high dielectric constant. The conductive material of the ring may be a highly conductive metal (e.g., aluminum) or a less conductive material (e.g., steel). Absorbing materials may be mounted on the conductive or reflective surfaces to suppress multitrack signal propagation.

[0018] Such a rotary joint can be used in the gantry of a CT scanner, the gantry comprising a stationary portion and a rotatable disk that rotates about a rotation axis. The rotatable disk can hold components such as a power supply, X-ray tube, X-ray detector, and data acquisition system. The rotary joint can receive data from the data acquisition system and couple this data to the stationary portion.

[0019] The gap can have a rectangular or square cross-section and can form a hollow cylindrical volume. Therefore, it can be described as a hollow rectangular or square toroid. Typically, the gap can be an empty space filled with air, but it can also include a dielectric material that can at least partially fill the gap. The circular gap can have a height corresponding to the radial distance between the first and second rings and a width corresponding to the width of the rings, wherein the height and width can be greater than twice the wavelength of the lowest frequency to be transmitted. If the rings have different widths, the width of the gap is determined by the smaller width.

[0020] In one embodiment, the first ring may be mounted and / or connected to the first sidewall, and the second ring may be mounted and / or connected to the second sidewall. This results in two parts that are rotatable relative to each other. Two sidewall gaps may exist between these two parts, which may be very close together, or the sidewall gaps may be bridged by a sliding contact, a spring, a washer, or any other means that can provide a low impedance between the two parts, which may be capacitive overlap. This improves shielding and avoids unwanted radiation. This is substantially the same if the first ring is mounted and / or connected to the second sidewall and the second ring is mounted and / or connected to the first sidewall.

[0021] In one embodiment, the first ring may be mounted to the first sidewall and the second sidewall such that the first ring is rotatable with the first sidewall and the second sidewall. To allow rotation, axial or radial sidewall gaps may be provided on both sides of the second ring, allowing the second ring to move freely relative to the first ring and the sidewall. An inverted embodiment may include a second ring mounted to the first sidewall and the second sidewall.

[0022] Basically, any combination of connected parts is possible, as long as the first ring is rotatable relative to the second ring. Any sidewall gaps between the rotatable parts can be bridged by sliding contacts, springs, washers, or any other means that can provide low resistance between the two parts, which can be capacitive overlap. The sidewall gaps can have a width of 0.5 to 4 mm, which is just large enough to allow for rotation and mechanical tolerances of an object of that size.

[0023] In one embodiment, the first ring and the second ring may have the same width and be axially aligned. Furthermore, the first sidewall and the second sidewall may be flat, disc-shaped rings covering the space between the first ring and the second ring. At least one of the sidewalls may overlap with at least one of the rings to bridge the sidewall gap between them and provide at least capacitive coupling. The overlap may be set to a size of one-quarter or a quarter of the wavelength.

[0024] In one embodiment, the distance between the first ring and the second ring is one of the following: equal to or less than twice the wavelength of the signal to be transmitted, or equal to or less than five times the wavelength. The distance can be five times the wavelength with a tolerance of ±50%. This allows for minimal dispersion between signal paths with the lowest and highest number of reflections.

[0025] In one embodiment, the first antenna and / or the second antenna has adjustable directivity, wherein the transmitted power and receiver sensitivity, as well as the conductivity of the reflective surfaces of the interior and the second ring, can be configured for a predetermined number of reflections between the rings, thereby resulting in a sufficiently low signal after one round of propagation.

[0026] In one embodiment, the first antenna and / or the second antenna are pointed into the circular gap. If a microwave signal is radiated into the gap, it will be reflected by the ring, allowing it to be received from the gap. Therefore, typically, embodiments can operate with non-specific antennas that simply radiate into and receive from the gap. Improved transmission can be achieved by pointing the first antenna at a first angle towards the second ring and the second antenna at a second angle towards the first ring. This ensures proper reflection through the ring to transmit signals that can be alternately reflected by the first and second rings. In another embodiment, the antennas can have configurable directivity. This means they have adjustable radiation patterns. This can be easily achieved with phased array antennas. The radiation pattern can be adjusted to obtain specific reflection angles, which can result in a well-defined signal path between the first and second antennas. Different or multiple signal paths can also exist. Too many different signal paths can have a negative impact if the diffusion—delay spread—caused by the difference in propagation time of the paths is too large to be compensated for by, for example, an equalizer. This can reduce transmission rate and / or transmission quality. In one example, there may be a first signal path with two reflections and another signal path with four reflections.

[0027] In one embodiment, at least one of the first antenna and the second antenna may be mounted flush with the surface of at least one of the first ring and the second ring. Alternatively, they may be mounted within the gap. They may be mounted at different radii and / or displaced in the direction of the axis of rotation. They may be mounted on a support structure outside the gap 250.

[0028] In one embodiment, the main beam of the at least one antenna can be redirected electronically or via a reflector. Such adjustment can be made before rotation and can be maintained without change during rotation.

[0029] In one embodiment, the first antenna and the second antenna can be configured for microwave or millimeter-wave signal connection.

[0030] Another embodiment relates to a data link between movable portions typically including a central gap. The central gap may have a linear shape, but it may also have any other shape, such as a combination of linear and / or curved segments. The central gap may include four sidewalls that may define a rectangular or square cross-section. This embodiment is similar to the circular gap embodiment disclosed herein. A linear central gap may include a first sidewall having a first antenna and a second sidewall opposite it having a second antenna. The first and second sidewalls may be parallel to each other to allow reflection between the first and second sidewalls. A third and fourth sidewall may be present on the sides of the first and second sidewalls to form the central gap.

[0031] The circular gap can have a height and a width. Furthermore, the linear intermediate gap can also have a height and a width. The gap can only guide microwave signals if the wavelength of the microwave signal is shorter than twice the width or twice the height (whichever is greater). The embodiment works best if at least one wavelength of multiple different microwave signals is shorter than 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 10, 1 / 20, 1 / 50, or 1 / 100 of the width or height (whichever is greater). The smaller the wavelength of the signal compared to the width or height of the gap, the more transmission paths are possible at different angles. Because microwave signals can be reflected between the first and second rings, or between the first and second sidewalls, at least one wavelength of the microwave signal can be shorter than 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 10, 1 / 20, 1 / 50, or 1 / 100 of this distance.

[0032] The distance between the first ring and the second ring can be significantly greater than half the wavelength of the transmitted signal to allow for multimode propagation of the signal.

[0033] In this document, the term microwave is used for radio frequency signals in the range greater than 300 MHz. In one embodiment, signals in the range above 2 GHz can be used. Very good transmission characteristics have been achieved for signals in the 60 GHz range. The embodiments may also use several frequencies of 100 GHz or higher.

[0034] In one embodiment, the data transmission implemented may conform to wireless standards such as IEEE 802.11 ad or ay.

[0035] The dimensions of the inner and second loops can be optimized to achieve a typical number of reflections during one round of microwave signal propagation. A strategy for optimizing the beam angle can be based on a defined antenna directivity to find an angle that results in a high-amplitude, narrow beam with strong attenuation and few sidelobes outside the beam. The same directivity distribution can exist at the receiver side. Furthermore, the beam angle may not be too close to 0° to avoid reflections from the opposite loops back into the antenna. This can be achieved using a two-dimensional patch antenna as a phased array antenna with sufficient angular resolution.

[0036] In an alternative embodiment, at least one of the first antenna and the second antenna may include a phased array antenna and / or a horn antenna, wherein the at least one antenna may have a directivity of at least 5 dBi.

[0037] Furthermore, reflection attenuation can be optimized by defining conductivity and reflection angle; higher conductivity of the material results in lower attenuation, and lower conductivity results in higher attenuation. This strategy aims to reduce dispersion (delay spread) between signals with varying numbers of reflections, as each reflection leads to higher attenuation.

[0038] A reflection angle can be defined by the directivity of the main beam of the antenna with the highest gain, and sidelobes may exist, but they experience high reflection attenuation, which further attenuates these paths, such that, for example, in the case of a narrow 3dB beamwidth of the antenna, for each location, most signal paths change only slightly relative to their total path length and angle.

[0039] Another way to reduce dispersion (delay spread) is to allow only a portion of the propagable path between the two antennas. This can be achieved by using antennas with a small 3dB beamwidth—antennas with high directivity that can reduce the number of paths. Paths with angles close to the beam angle have small path length differences and transmit most of the energy because they experience high antenna gain. Other paths outside the main beam, such as paths in the sidelobe region, may be attenuated too much to significantly affect transmission. The wider the beamwidth that can be selected and the larger the rotation angle, the more paths can fall within the beamwidth—e.g., a 3dB beamwidth—and the greater the dispersion that can occur. Therefore, the beamwidth can be chosen to be narrow enough that for a full rotation with a 360° rotation angle, the dispersion can be sufficiently small.

[0040] Axial displacement of the transmitter and receiver can reduce the dynamic range of received signal strength between the minimum signal path 0 degrees and the signal path 360 degrees.

[0041] At rotation angles close to 0°, signal attenuation can be minimized when the first and second antennas are close to each other. The range between the attenuation occurring at this rotation angle and the maximum possible attenuation during the full rotation determines the dynamic range requirements of the transmission system. To keep this value as low as possible, the antennas can be axially shifted to increase the path length for this rotation angle range and to create a propagation path extending at the edge or outside of the main beam between the two antennas.

[0042] One embodiment may use features of wireless standards—such as, for example, IEEE 802.11 ad or ay—with a guard interval along with OFDM or a single carrier with frequency domain equalization. The transceiver may periodically train the characteristics of the gap. Multiple transmission paths may be employed, such as clockwise and counterclockwise transmission. A standard guard interval may be selected such that it is longer than the total signal propagation time through the gap covering the entire track (360 degrees) of the rotary joint gap. For a given guard interval and a given minimum diameter of the first ring, the distance between the first ring and the second ring can be adapted to obtain a predetermined maximum path length resulting in a predetermined maximum signal propagation time.

[0043] The guard interval of the aforementioned wireless standard can be used to allow for dispersion caused by multipath propagation and dispersion caused by one or more tracks. Training may be possible to optimize the guard interval.

[0044] The attenuating material can be mounted axially relative to and near the antenna in at least one of the rings to attenuate a portion of the signal that has propagated beyond a full loop, thereby reducing interference between the directly received signal and the signal that has propagated beyond a full loop.

[0045] Several parallel gaps may exist, arranged radially or axially. An axial arrangement is preferred, where multiple antennas have sidewalls to separate the gaps. Therefore, when sufficient attenuation exists between the gaps, the overall transmission capacity can be increased.

[0046] In one embodiment, the first antenna may be electrically coupled to a transmitter, and the second antenna may be electrically coupled to a receiver. In another embodiment, the first antenna may be electrically coupled to a receiver, and the second antenna may be electrically coupled to a transmitter. In yet another embodiment, the first antenna may be electrically coupled to a first transceiver, and the second antenna may be electrically coupled to a second transceiver. The transmission and reception frequencies at the transceivers may be different to achieve better signal separation between communication channels.

[0047] In one embodiment, the rotary joint may have a first component and a second component, wherein the first component may be rotatable relative to the second component. The first antenna may be located at the first component, and the second antenna may be located at the second component. The first ring and the second ring may be located at either component. Attached Figure Description

[0048] The invention will now be described by way of example rather than limitation of the general inventive concept, with reference to the accompanying drawings and examples of embodiments.

[0049] Figure 1 An example is shown.

[0050] Figure 2 A cross-sectional side view of the circular gap is shown.

[0051] Figure 3 A cross-sectional side view without sidewalls is shown.

[0052] Figure 4 A front view of the circular gap is shown.

[0053] Figure 5 An embodiment with an antenna within the gap is shown.

[0054] Figure 6 Another front view of the circular gap is shown.

[0055] Figure 7 This demonstrates multipath propagation.

[0056] Figure 8 This illustrates two-path propagation.

[0057] Figure 9 A linear embodiment is shown.

[0058] Figure 10 An exemplary functional block diagram is shown.

[0059] Figure 11 An exemplary relationship between beam and beam angle is shown.

[0060] exist Figure 1 The first embodiment is shown in the diagram. The gantry 100 of the CT scanner includes a stationary portion 102 and a rotatable portion 150, the rotatable portion including a rotatable disk 104 rotatable about a rotation axis 110. This rotatable disk can hold rotatable components (not shown here), such as a power supply, X-ray tube, X-ray detector, and data acquisition system. Furthermore, a slip ring or rotatable power transformer (also not shown) can be configured to transfer power from the stationary portion to the rotatable portion.

[0061] The rotatable portion 150 may include a rotary joint 200 for high-speed data transmission. The rotary joint 200 may include a first ring 210 and a second ring 220, both rings being coaxial. This embodiment will also operate with an offset axis. The two rings may be rotatable relative to each other. Either ring may be stationary while the other is rotatable.

[0062] Furthermore, a first sidewall 230 and / or a second sidewall 240 may be provided. Additionally, at least one of the sidewalls may be part of the gantry 100 of the CT scanner. Each sidewall may be fixed to one of rings 210, 220. A low-impedance contact may also exist between a sidewall and a ring. To the other ring, a sidewall gap may exist, which may be bridged by a sliding brush, a conductive washer, or any other suitable material that can provide good electrical contact.

[0063] In one embodiment, ring 210 and the two sidewalls 230, 240 may be connected together to form a U-shaped cross-section, while ring 220 is rotatable. Sidewall gaps may exist on the sides of the second ring 220 to allow rotation. Any other combination of connected portions may exist, allowing rings 210 and 220 to rotate together with their mechanically coupled antennas 211 and 221, and may form an annulus with a rectangular cross-section together with the sidewalls.

[0064] The two rings 210 and 220 may have the same width and may be axially aligned. The sidewalls 230 and 240 may be flat disc-shaped rings, and they may also overlap with at least one of the first ring 210 and the second ring 220.

[0065] Rings 210, 220 and sidewalls 230, 240 comprise conductive materials (e.g., metals) and / or materials having conductive surfaces.

[0066] The first antenna 211 is rotatable relative to the second antenna 221. Both antennas point into the volume between the rings. The antennas can rotate with their rings or remain stationary with their rings; the antennas can be mounted onto the rings.

[0067] Figure 2 A cross-sectional side view of one embodiment of a rotary joint 200 with sidewalls is shown. The rotary joint may have a rectangular or square cross-section with a width of 251 between sidewalls 230 and 240 and a height of 252 between rings 210 and 220.

[0068] The rotary joint 200 has an internal space that allows the propagation of electromagnetic waves with a maximum wavelength λmax equal to twice the width 251 or the height 252 (whichever is greater).

[0069] Since sidewalls 230 and 240 are not functionally necessary, they can be omitted; therefore, the width of the gap can be the minimum width of rings 210 and 220. Figure 3 Such an embodiment is shown in the figure.

[0070] Figure 3 A cross-sectional side view similar to the previous figure is shown, but without sidewalls 230 and 240. Here, some radiated energy may be lost through the open sides, but a considerable portion of the radiation remains guided between the rings.

[0071] Figure 4 A front view of the circular gap 250 is shown, showing possible signal paths between the first antenna 211 and the outer antenna 221. The signal can be transmitted not only in a single mode within the circular gap 250, but it can also be reflected at the first ring 210 and / or the second ring 220. In this figure, the first antenna 211 and the outer antenna 221 can have a relative angle (rotation angle) of approximately 180 degrees. The first antenna 211 can transmit a signal with a first beam 341 at an angle 331 relative to the radial direction 112. Here, the radial direction lies on a line 112 that passes through the rotation axis 110 at a right angle. As shown and depending on the specific radiation direction of the antenna, multiple reflections can occur at the rings. For each reflection, the angles of the reflected electromagnetic wave 310 and the reflected wave relative to the surface of the rings are the same. Thus, the first reflection angle at the second ring 311 is the same as the second reflection angle at the second ring 312, and the first reflection angle at the first ring 313 is the same as the second reflection angle at the first ring 314. The second antenna 221 can receive signals with a second beam 342 at an angle 332 relative to the radial direction 332. Here, the sum of reflection angles 311 (or 312) and 332 can be 90°, as can the sum of reflection angles 313 (or 314) and 331. Here, the beam is indicated only by its centerline. In addition to the beam angle, which is the angle of maximum radiation level, the antenna beam can also be characterized by 3dB or half-power beamwidth. Half-power beamwidth is the angular width (in degrees) of the main beam or lobe of the antenna radiation pattern, at which the signal power is half of its peak value. Because the antenna is reciprocal, the transmission and reception functions can be interchanged. Here, the first antenna 211 and the second antenna 221 can be located at the first loop 210 and the second loop 220. They can be attached to the loops and radiate through the holes in the loops.

[0072] Figure 5An embodiment similar to the previous figure is shown. Here, the first antenna 211 and the second antenna 221 are located within the gap 250. They can be mounted on different radii and / or displaced in the direction of the rotation axis 110. They can be mounted on a support structure outside the gap 250.

[0073] Figure 6 Another front view of the rotary joint 200 toward the circular gap 250 between the first ring 210 and the second ring 220 is shown. In this figure, the first antenna 211 and the second antenna 221 have a relative angle of approximately 0 degrees, such that they are opposite each other. Here, electromagnetic waves 310 can propagate directly from the first antenna 211 to the second antenna 221. During rotation, the relative angle between the antennas changes continuously, and the 0-degree position shown here, as well as other relative angles shown in other figures, exist only for a short time.

[0074] Figure 7 Multipath propagation is illustrated. In this figure, the first antenna 211 and the second antenna 221 have a relative angle of approximately 180 degrees. Three different multipath propagations 316, 317, and 318 are shown here. With a small 3dB beamwidth, the antennas help minimize dispersion caused by multiple paths with different propagation times by attenuating paths with longer or shorter propagation lengths.

[0075] Figure 8 An embodiment with dual-path propagation is shown. In this figure, the first antenna 211 and the second antenna 221 have a relative angle of approximately 270 degrees. Here, electromagnetic wave 310 can propagate clockwise from the first antenna 211 to the second antenna 221. A second counterclockwise signal path 315 may also exist, which can contribute to signal reception if the antenna gain at a given beam angle is sufficiently high and the attenuation due to reflection is sufficiently low. To enable the receiver's equalizer to compensate for the effects of the sum of the two signals, a guard interval can cover at least one propagation time around the 360 ​​degrees of the rotary joint. Signals along the two paths are alternately reflected by the first and second loops. Furthermore, both signal paths can be used for bidirectional signal transmission. This example shows a relative angle of approximately 270 degrees, but both signal paths are substantially available across all relative angles between the first antenna 211 and the second antenna 221.

[0076] Figure 9A linear embodiment is shown. The central gap 400 includes four sidewalls 410, 420, 430, 440, thereby defining a hollow space with a rectangular or square cross-section. The first sidewall 410 is parallel to the second sidewall 420. Furthermore, a first antenna 411 is mechanically coupled to the first sidewall 410, and the second antenna 421 is movable within the linear gap. The second antenna is mechanically coupled to the second sidewall. The sidewalls 410, 420, 430, 440 comprise a conductive material, such as metal. They may be made of such a material, or they may have conductive surfaces that may include such a material. The first antenna 411 and the second antenna 421 are configured for a microwave signal connection 169 between them. This embodiment is substantially the same as the circular embodiment disclosed herein, but is linear. The first sidewall 410 corresponds to a first ring 210, and the second sidewall 420 corresponds to a second ring 220. Furthermore, an embodiment may have any shape, such as a combination of curved segments and / or linear segments.

[0077] Figure 10 An exemplary functional block diagram is shown. A transmitter 161, fed by a data acquisition system providing imaging data, sends signals to a first antenna 211, which radiates microwave signals 169 into a circular gap 250. These RF signals 169 are received by antenna 221 and forwarded to receiver 162. Essentially, the direction can be reversed. Bidirectional communication is also possible.

[0078] Figure 11 An exemplary relationship between beamwidth and beam angle is shown. A larger beam angle allows for a larger beamwidth that can be set. This relationship limits dispersion caused by multipath delay spread. This relationship is valid for the first antenna shown here, but also applies to the second antenna. Here, the first antenna 211 has a first beamwidth 171 (3dB width) and a first beam angle 181. In one case, the first antenna has a second beamwidth 172 greater than the first beamwidth, and therefore the corresponding second beam angle 182 will be greater than the first beam angle 172. Both beamwidths are defined as 3dB (half-power) beamwidths.

[0079] List of reference numerals

[0080] 100CT scanner rack

[0081] 102 stationary parts

[0082] 104 rotatable discs

[0083] 110 Rotation Axis

[0084] 112 radial direction

[0085] 150 rotatable part

[0086] 161 transmitter

[0087] 162 receiver

[0088] 169RF signal

[0089] 171 First beamwidth

[0090] 172 Second beamwidth

[0091] 181 First beam angle

[0092] 182 Second beam angle

[0093] 200 rotary joint

[0094] 210 First Ring

[0095] 211 First Antenna

[0096] 220 Second Ring

[0097] 221 Second Antenna

[0098] 230 First sidewall

[0099] 240 Second sidewall

[0100] 250 gap

[0101] 251 width

[0102] 252 Height

[0103] 310 Electromagnetic wave propagation

[0104] 311 First reflection angle at the second ring

[0105] 312 Second reflection angle at the second ring

[0106] 313 First reflection angle at the first ring

[0107] 314 Second reflection angle at the first ring

[0108] 315 Alternating electromagnetic wave propagation

[0109] 316 First Multipath Propagation

[0110] 317 Second Multipath Propagation

[0111] 318 Third multipath propagation

[0112] 331 First beam angle

[0113] 332 Second beam angle

[0114] 341 First Beam

[0115] 342 Second Beam

[0116] 400 medium space gap

[0117] 410 First sidewall

[0118] 420 Second sidewall

[0119] 411 First Antenna

[0120] 420 Second sidewall

[0121] 421 Second Antenna

[0122] 430 Third sidewall

[0123] 440 Fourth sidewall

[0124] 451 width

[0125] 452 Height

Claims

1. A high-speed data link rotary joint (200) include: A first ring (210) having a first diameter (212) and a second ring (220) having a second diameter (222) larger than the first diameter (212). The first ring (210) and the second ring (220) are arranged coaxially around the central axis (110), thereby forming a circular gap (250) between the first ring (210) and the second ring (220). The first ring (210) and the second ring (220) comprise at least partially conductive material. The rotary joint (200) also includes a first antenna (211) and a second antenna (221) that can rotate relative to the first antenna (211). The first antenna (211) is directed in the circular gap (250) in a first direction (341) and at a first beam angle, which is referred to as the first angle (331). The second antenna (221) is directed in a second direction (342) opposite to the first direction (341) and at a second beam angle into the circular gap (250), the second beam angle being referred to as the second angle (332). The first angle (331) and the second angle (332) relative to the radial direction (112) of the central axis (110) have absolute values ​​in the range of 1° to 89°. The first angle (331) and the second angle (332) are at fixed values ​​that remain constant with rotation. The first antenna (211) and the second antenna (221) are configured for microwave or millimeter-wave signal connection, wherein the distance between the first ring and the second ring is five times the wavelength of the microwave or millimeter-wave signal and has a tolerance of ±50%.

2. The rotary joint according to claim 1, Its features are, No sidewall is provided between the first ring (210) and the second ring (220).

3. The rotary joint according to claim 1 or 2, Its features are, The circular gap (250) has a rectangular cross-section and is capable of having a hollow cylindrical volume.

4. The rotary joint according to claim 1 or 2, Its features are, The circular gap (250) has a height and a width, the height corresponding to the radial distance between the first ring (210) and the second ring (220), wherein the height and the width are greater than twice the wavelength of the lowest frequency to be transmitted.

5. The rotary joint according to claim 1 or 2, Its features are, The absolute value of the first angle (331) is equal to the absolute value of the second angle (332).

6. The rotary joint according to claim 1 or 2, Its features are, The first antenna (211) and the second antenna (221) are axially displaced.

7. The rotary joint according to claim 1 or 2, Its features are, The first antenna (211) is mechanically coupled to the first ring (210) and / or the second antenna (221) is mechanically coupled to the second ring (220).

8. The rotary joint according to claim 1 or 2, Its features are, The first antenna (211) and the second antenna (221) have radiation patterns that are constant with rotation.

9. The rotary joint according to claim 1 or 2, Its features are, The microwave or millimeter-wave signal can be alternately reflected by the first ring (210) and the second ring (220).

10. The rotary joint according to claim 1 or 2, Its features are, The absolute value of the first angle (331) is greater than the 3dB beamwidth of the first antenna (211), and / or The absolute value of the second angle (332) is greater than the 3dB beamwidth of the second antenna (221).

11. The rotary joint according to claim 1 or 2, Its features are, The first antenna (211) is electrically coupled to the transmitter, and the second antenna (221) is electrically coupled to the receiver, or The first antenna (211) is electrically coupled to the receiver, and the second antenna (221) is electrically coupled to the transmitter, or The first antenna (211) is electrically coupled to the first transceiver, and the second antenna (221) is electrically coupled to the second transceiver.

12. The rotary joint according to claim 11, Its features are, The transmitter and the receiver are configured for, or the first transceiver and the second transceiver are configured for, OFDM or a single carrier with frequency domain equalization.

13. The rotary joint according to claim 1 or 2, Its features are, At least one of the first antenna (211) and the second antenna (221) includes a phased array and / or a horn antenna, wherein the at least one antenna is capable of having directivity of at least 5 dBi.

14. The rotary joint according to claim 1 or 2, Its features are, At least one of the first antenna (211) and the second antenna (221) is mounted flush with the surface of at least one of the first ring (210) and the second ring (220), wherein the main beam of the at least one antenna can be electronically or by means of a reflector.

15. The rotary joint according to claim 1 or 2, Its features are, At least one of the first ring (210) and the second ring (220) Including electromagnetic reflective materials, or Having a conductive surface, or This includes dielectric materials with high dielectric constants.

16. The rotary joint according to claim 15, Its features are, The electromagnetic reflection material is a conductive material.

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