Rotational transmission system using waveguides

Abstract

A coupler provides a high speed data link between rotating parts, the coupler comprising an annular channel encircling a hollow cylindrical volume and at least two antennas. The annular channel comprises an electrically conductive material and comprises an inner ring, an outer ring which can rotate relative to the inner ring, and two side walls on two sides of the ring. An inner antenna is mechanically coupled to the inner ring, and an outer antenna is mechanically coupled to the outer ring. The antennas are configured for microwave signal connection between the antennas based on multiple reflections at the ring.

Description

Technical Field

[0001] This invention relates to a rotary transmission system for providing a non-contact, high-speed data link between rotating devices, and is particularly suitable for computed tomography scanners. Background Technology

[0002] Non-contact data links can be used to couple rotating devices to stationary parts, such as the rotating part of a computed tomography (CT) scanner gantry. Data rates range from 1 Gbit / s to over 10 Gbit / s. Such data links can also be called rotary joints or slip rings.

[0003] Because CT scanners have a large internal aperture for accommodating the patient being scanned, the rotary joints used in CT scanners must have a large diameter, typically ranging from 1 m to 1.5 m. US 5,646,962 discloses such a non-contact rotary joint based on a stripline and a capacitive pickup. The stripline is used to guide signals around a ring-shaped body, and the capacitive pickup can be moved to the ring-shaped body to receive the signals.

[0004] Another method disclosed in EP 0 093 468 uses a waveguide to transmit signals. A stationary waveguide comprising a conductive hollow body in the shape of a ring has a fixed receiving antenna. Furthermore, a rotatable transmitting antenna can move within the body in radial slots to couple signals into the interior of the waveguide. These signals propagate along the waveguide until they reach the receiving antenna.

[0005] The problem is that the waveguide's relative bandwidth is relatively small, 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 be fitted into these slots and therefore can only have small pins. This limits the antenna's 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 the problem is described in the independent claims. The dependent claims relate to further improvements to the invention.

[0008] The rotary joint includes an annular channel that contains a high-speed data link between rotatable parts. The annular channel may contain an inner ring and an outer ring. The two rings can rotate relative to each other about an axis, which may be the rotation axis of the rotary joint. The outer ring has a larger diameter than the inner ring, thus providing a radial clearance or space between the rings. Additionally, the inner and outer rings can be axially aligned. Essentially, either ring can be stationary while the other is rotatable.

[0009] The annular channel may also include at least one or two sidewalls. A first sidewall is axially located on one side of the ring, while a second sidewall is axially located on the other or opposite side of the ring. The inner ring, outer ring, first sidewall, and second sidewall form the annular channel, which may have a rectangular or square cross-section. Essentially, any one of the sidewalls may be stationary or rotatable.

[0010] Sidewalls are not essential for the transmission function of the channel, but they can help decouple signals transmitted from the environment or adjacent channels by using reflective or absorptive sidewalls. Therefore, standard wireless buses, such as those of IEEE 802.11, can also be used without interfering with the installation of external wireless buses for other purposes.

[0011] For signal transmission, the inner antenna is mechanically coupled to the inner loop, and the outer antenna is mechanically coupled to the outer loop. The inner and outer antennas are directed into the space between the inner and outer loops. This allows microwave signals to be transmitted between the inner and outer antennas if one antenna radiates a signal into the channel and the other receives the signal from the channel. The channel, and specifically the inner and outer loops, can reflect the microwave signal, allowing it to propagate through the loops. To improve signal reflection, the channel, and specifically the loops and / or sidewalls, can contain a conductive material, which may be metallic. The loops and / or sidewalls can be made of such a conductive material, or the loops and / or sidewalls can have surfaces coated with such a conductive material.

[0012] The rings (210, 220) and / or sidewalls (230, 240) may be electromagnetic reflective materials, such as conductive materials, or have conductive surfaces, or be dielectric materials with high dielectric constants.

[0013] This rotary joint can be used in the gantry of a CT scanner, which includes a stationary section and a rotating disk that rotates about a rotation axis. The rotating disk may contain 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 section.

[0014] The channel can have a rectangular or square cross-section. Therefore, a channel can be described as a hollow rectangular or square ring. Typically, a channel can be a void filled with air, but it can also contain a dielectric material that at least partially fills the channel.

[0015] In one embodiment, the inner ring may be mounted and / or connected to the first sidewall, and therefore the outer ring may be mounted and / or connected to the second sidewall. This results in two parts that can rotate relative to each other. Two gaps may exist between these two parts, which may be very close together or bridged by a sliding contact, spring, washer, or any other means that can provide low resistance between the two parts, such as a capacitive overlap. This improves shielding and avoids unwanted radiation. It is essentially the same if the inner ring is mounted and / or connected to the second sidewall and the outer ring is mounted and / or connected to the first sidewall.

[0016] In one embodiment, the inner ring can be mounted to both a first sidewall and a second sidewall, allowing the inner ring to rotate together with both sidewalls. To allow rotation, gaps can be provided on both sides of the outer ring, allowing the outer ring to move freely relative to the inner ring and the sidewalls. An inverted embodiment may include an outer ring mounted to both the first and second sidewalls.

[0017] Basically, any combination of the connecting parts is possible, as long as the inner ring can rotate relative to the outer ring. Any gap between the rotatable parts can be bridged by a sliding contact, spring, washer, or any other device that can provide low resistance between the two parts, such as a capacitive overlap. The gap can have a width of 0.5 mm to 4 mm, which is just large enough to allow for rotation and mechanical tolerances of objects of that size.

[0018] In this embodiment, the inner and outer rings may have the same width and be axially aligned. Additionally, the first and second sidewalls may be flat disc-shaped rings that cover the space between the inner and outer rings. At least one sidewall may overlap with at least one ring to bridge the gap between the sidewall and the ring and to provide at least capacitive coupling. The overlap may be sized to one-quarter or more of the wavelength.

[0019] In this embodiment, the distance between the inner and outer rings is approximately five times the wavelength. The distance can be five times the wavelength, with a tolerance of ±50%. This allows for the lowest possible dispersion between the signal path with the lowest number of reflections and the signal path with the highest number of reflections.

[0020] In one embodiment, the inner and / or outer antennas have adjustable directivity, wherein the transmit power and receiver sensitivity, along with the conductivity of the reflective surfaces of the inner and outer rings, can be configured for a predetermined number of reflections between the rings, thereby generating a sufficiently low signal after one loop of propagation.

[0021] In this embodiment, the inner and / or outer antennas are directed into the loop channel. If a microwave signal is radiated into the channel, it will be reflected through the channel, allowing it to be received from the channel. Therefore, typically, the embodiment can operate with a simple non-specific antenna radiating into and receiving from the channel. Improved transmission can be achieved by directing the inner antenna toward the outer loop and the outer antenna toward the inner loop. This ensures proper reflection through the loop for signal delivery. In another embodiment, the antenna can have configurable directivity. This means the antenna has an adjustable radiation pattern. This can be easily achieved with a phased array antenna. The radiation pattern can be adjusted to achieve a specific reflection angle that creates a well-defined signal path between the inner and outer antennas. Different or multiple signal paths can also exist, which can be further used for multiple channels. This can increase transmission rate and / or transmission quality. In the example, there can be a first signal path with two reflections and another signal path with three reflections. Due to the different reflection angles of the signal paths, the signal paths can be well separated by selective antennas. Any number of signal paths can exist.

[0022] Another embodiment relates to a data link between movable portions, which typically include a hollow channel. The hollow channel can have a linear shape, but can also have any other shape, such as a combination of linear segments and / or curved segments. The hollow channel can include four sidewalls, which can define a rectangular or square cross-section. This embodiment is comparable to the annular channel embodiment disclosed herein. The linear hollow channel can include a first sidewall and a second sidewall, the first sidewall having a first antenna, and a second sidewall opposite the first sidewall having a second antenna. The first and second sidewalls can be parallel to each other to allow reflection between the first and second sidewalls. A third and fourth sidewall can be present at the sides of the first and second sidewalls to form the hollow channel.

[0023] A ring-shaped channel can have both height and width. A linear hollow channel can also have both height and width. The channel can guide a microwave signal if the wavelength of the microwave signal is shorter than twice the greater of the width or height. The embodiment is most effective if at least one wavelength of the microwave signal is shorter than 1 / 2, 1 / 3, 1 / 4, 1 / 5, or 1 / 10, or 1 / 20, or 1 / 50, or 1 / 100 of the greater of the width or height; the microwave signal can have multiple different wavelengths. The smaller the wavelength of the signal compared to the width or height of the channel, the more transmission paths are possible at different angles. Since the primary transmission can be reflection between the inner and outer rings, or reflection 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, or 1 / 10, or 1 / 20, or 1 / 50, or 1 / 100 of this distance.

[0024] The distance between the inner and outer rings can be significantly greater than half the wavelength of the transmitted signal to allow for multi-mode propagation of the signal.

[0025] In this document, the term microwave is used for radio frequency signals with a range greater than 300 MHz. In embodiments, signals in the range above 2 GHz can be used. Signals in the 60 GHz range have achieved very good transmission characteristics. Embodiments may also use frequencies of several hundred GHz or higher.

[0026] In this embodiment, the data transmission may conform to wireless standards such as IEEE 802.11ad or IEEE 802.11ay.

[0027] The dimensions of the inner and outer rings can be optimized to achieve a typical number of reflections during a microwave signal propagation loop. The strategy for optimizing the angle is to find an angle where the antenna has defined directivity, resulting in a high-amplitude, narrow transmit beam, strong out-of-beam attenuation, and few sidelobes. The same directivity distribution can exist on the receive side. The angle can also be less steep, allowing reflections at opposite rings to return to the antenna. This can be achieved by using a two-dimensional patch antenna as a phased array antenna with sufficient angular resolution.

[0028] Reflection attenuation, defined by conductivity and reflection angle, can also be optimized; higher conductivity in the material results in lower attenuation, and lower conductivity results in higher attenuation. The strategy aims to reduce dispersion (delay spread) between signals with different numbers of reflections, as each reflection leads to higher attenuation.

[0029] A reflection angle is preferred for the directivity of the antenna’s main beam, and sidelobes may exist, but they will experience higher reflection attenuation, which will further attenuate these paths, so that most of the signal paths change only slightly in terms of the total path length and angle of the signal path.

[0030] Axial displacement of the transmitter and receiver can reduce the dynamic range of received signal strength between 0 degrees of minimum signal path and 360 degrees of signal path.

[0031] The attenuating material can be mounted axially to at least one of the antennas in the loop and near the antenna to attenuate the portion of the signal propagating beyond a full loop, thereby reducing interference between the directly received signal and the signal propagating beyond a full loop.

[0032] The implementation can utilize features of wireless standards such as IEEE 802.11 ad or IEEE 802.11 ay: a guard interval along with OFDM or a single carrier with frequency domain equalization. The transceiver can periodically train the channel characteristics and can employ multiple transmission paths, such as clockwise and counter-clockwise transmission. The guard interval of the applied standard can be selected such that the guard interval is shorter than the signal propagation time through the channel. For a given guard interval, the distance between the inner and outer loops can be adapted to obtain a predetermined maximum path length, thereby producing a predetermined maximum signal propagation time.

[0033] The guard intervals mentioned above in wireless standards can be used to allow multipath propagation. Training to optimize the guard intervals is possible.

[0034] Several parallel channels can exist, arranged radially or axially. An axial arrangement preferably has multiple coupled antennas, with sidewalls to separate the channels. Therefore, with sufficient attenuation between the channels, the total transmission capacity can be increased.

[0035] The transmit and receive frequencies at the transceiver can be different to achieve better signal separation between communication channels. Attached Figure Description

[0036] In the following description, without limiting the general concept of the invention, the invention will be described by way of example of embodiments with reference to the accompanying drawings.

[0037] Figure 1 An example is shown.

[0038] Figure 2 A cross-sectional side view of the annular channel is shown.

[0039] Figure 3 A front view of the annular channel is shown.

[0040] Figure 4 Another front view of the annular channel is shown.

[0041] Figure 5 This illustrates two-path propagation.

[0042] Figure 6 This demonstrates multipath propagation.

[0043] Figure 7 A linear embodiment is shown.

[0044] Figure 8 An exemplary functional block diagram is shown.

[0045] exist Figure 1 The first embodiment is shown. The CT scanner gantry 100 includes a stationary portion 102 and a rotating disk 104 that rotates about a rotation axis 110. The rotating disk may include rotating components such as a power supply, X-ray tube, X-ray detector, and data acquisition system, which are not shown here. Additionally, a slip ring or rotating power transformer may be provided for transmitting power from the stationary portion to the rotating portion; this slip ring or rotating power transformer is also not shown.

[0046] The rotary joint 150 for high-speed data transmission includes an annular channel 200. Channel 200 can be described as a hollow rectangular or square ring. Channel 200 surrounds a hollow cylindrical volume. Channel 200 may include an inner ring 210 and an outer ring 220, both rings being coaxial. Embodiments also apply to offset axes. Both rings can rotate relative to each other. Either ring can be stationary while the other can be rotatable.

[0047] To form channel 200, a first sidewall 230 and / or a second sidewall 240 may be provided. At least one of the sidewalls may also be part of the CT scanner gantry 100. Each sidewall may be fixed to one of rings 210, 220. Low-impedance contact may also exist between the sidewall and the ring. For the other ring, a 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.

[0048] In one embodiment, ring 210 and the two sidewalls 230, 240 can be joined together to form a U-shaped cross-section, while ring 220 is rotatable. A gap may exist at the side of the outer ring 220 to allow rotation. Any other combination of connecting portions may exist, allowing rotation of rings 210 and 220 with antennas 211 and 221 mechanically coupled to them, and may form a ring with a rectangular cross-section together with the sidewalls.

[0049] The two rings 210 and 220 may have the same length and may be axially aligned. The sidewalls 230 and 240 may be flat disc-shaped rings, which may also overlap with at least one of the inner ring 210 and the outer ring 220.

[0050] Rings 210, 220 and sidewalls 239, 240 include conductive materials, such as metals and / or materials with conductive surfaces.

[0051] The inner antenna 211 is located at the inner ring 210, while the outer antenna 221 is located at the outer ring 220. The antenna can rotate or remain stationary together with the ring, and the antenna is mounted to the ring.

[0052] Figure 2 A cross-sectional side view of the annular channel 200 is shown. The channel may have a rectangular or square cross-section, wherein it has a width 251 between the sidewalls 230 and 240, and a height 252 between the rings 210 and 220.

[0053] The waveguide has an inner space that allows the propagation of electromagnetic waves with a maximum wavelength λk equal to twice the larger of width 251 or height 252.

[0054] Since sidewalls 230 and 240 are not necessary for the function, they can be omitted. Therefore, the width of the channel can be the minimum width of rings 210 and 220.

[0055] Figure 3 A front view of a ring channel 200 is shown, in which a signal path may exist between the inner antenna 211 and the outer antenna 221. The signal can be transmitted not only in a single model within the ring channel 200, but can also be reflected at the inner ring 210 and / or the outer ring 220. In this figure, the inner antenna 211 and the outer antenna 221 have a relative angle of approximately 180 degrees. As shown, multiple reflections may occur at the rings, depending on the specific radiation direction of the antennas. For each reflection, the angle of the electromagnetic wave 310 to be reflected relative to the surface of the ring and the angle of the reflected wave relative to the surface of the ring are the same. Thus, the first angle 311 at the outer ring is the same as the second angle 312 at the outer ring, and the first angle 313 at the inner ring is the same as the second angle 314 at the inner ring.

[0056] Figure 4 A further front view of the annular channel 200 is shown. In this figure, the inner antenna 211 and the outer antenna 221 have a relative angle of approximately 0 degrees, such that the inner antenna 211 and the outer antenna 221 are opposite each other. Here, electromagnetic waves 310 can propagate directly from the inner antenna 211 to the outer antenna 221.

[0057] Figure 5This illustrates dual-path propagation. In this figure, the inner antenna 211 and the outer antenna 221 have a relative angle of approximately 270 degrees. Here, electromagnetic wave 310 can propagate clockwise from the inner antenna 211 to the outer antenna 221. If the antennas are configured to radiate accordingly, a second counter-clockwise signal path 315 may also exist. The antenna and / or transmitter and / or receiver can switch between these signal paths to select the optimal path. The two signal paths can also be used to increase the data rate. Additionally, both signal paths can be used for bidirectional signal transmission. This example shows a relative angle of approximately 270 degrees, but essentially two signal paths are available across all relative angles between the inner antenna 211 and the outer antenna 221.

[0058] Figure 6 Multipath propagation is illustrated. In this figure, the inner antenna 211 and the outer antenna 221 have a relative angle of approximately 180 degrees. Three different multipath propagations 316, 317, and 318 are shown here. This can be used to further increase the bandwidth.

[0059] Figure 7 A linear embodiment is illustrated. The hollow channel 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. Additionally, a first antenna 411 is mechanically coupled to the first sidewall 410, and the second antenna 421 is movable within the linear channel. A second antenna may be coupled to the second sidewall. The sidewalls 410, 420, 430, 440 comprise a conductive material, such as metal. The sidewalls 410, 420, 430, 440 may be made of this material or may have conductive surfaces that can contain this material. The first antenna 411 and the second antenna 421 are configured for microwave signal connection 169 between the sidewalls 410, 420, 430, 440. This embodiment is substantially the same as the annular embodiment disclosed herein, but is linear. The first sidewall 410 corresponds to the inner ring 210, and the second sidewall 420 corresponds to the outer ring 220. Additionally, the embodiment can have any shape, such as a combination of curved segments and / or linear segments.

[0060] Figure 8 An exemplary functional block diagram is shown. Transmitter 161 sends signals to inner antenna 211, which can be supplied by a data acquisition system providing imaging data. Inner antenna 211 radiates microwave signals 169 into the loop channel 200. These RF signals 169 are received via antenna 221 and forwarded to receiver 162. Essentially, the direction can be reversed. Bidirectional communication is also possible.

[0061] List of reference numerals

[0062] 100CT scanner stand

[0063] 102 stationary parts

[0064] 104 rotatable discs

[0065] 110 Rotation Axis

[0066] 150 rotary joint

[0067] 161 transmitter

[0068] 162 receiver

[0069] 169RF signal

[0070] 200 Circular Channel

[0071] 210 Inner Ring

[0072] 211 internal antenna

[0073] 220 Outer Ring

[0074] 221 external antenna

[0075] 230 First sidewall

[0076] 240 Second sidewall

[0077] 251 width

[0078] 252 meters high

[0079] 310 Electromagnetic wave propagation

[0080] 311 at the first angle on the outer ring

[0081] 312 at the second angle on the outer ring

[0082] 313 at the first angle of the inner ring

[0083] 314 at the second angle of the inner ring

[0084] 315 Alternating Electromagnetic Wave Propagation

[0085] 316 First Multipath Propagation

[0086] 317 Second Multipath Propagation

[0087] 318 Third Multipath Propagation

[0088] 400 Hollow Channel

[0089] 410 First sidewall

[0090] 420 Second sidewall

[0091] 411 First Antenna

[0092] 420 Second sidewall

[0093] 421 Second Line

[0094] 430 Third sidewall

[0095] 440 Fourth sidewall

[0096] 451 width

[0097] 452 meters high

Claims

1. A rotary joint that provides a high-speed data link between rotatable portions, the rotary joint including an annular channel (200). The annular channel (200) includes: -Inner ring (210) and outer ring (220). The inner ring (210) and the outer ring (220) are both centered about a common axis of rotation (110) and are capable of rotating relative to each other. The outer ring (220) has a larger diameter than the inner ring (210). - Inner antenna (211), said inner antenna (211) being mechanically coupled to said inner ring (210), and - External antenna (221), which is mechanically coupled to the outer ring (220). in, The inner antenna (211) and the outer antenna (221) are guided into the space between the inner ring (210) and the outer ring (220) and configured for microwave signal (169) connection between the inner antenna (211) and the outer antenna (221), wherein the distance between the inner ring and the outer ring is approximately five times the wavelength of the microwave signal, wherein the tolerance is ±50%.

2. The rotary joint according to claim 1, Its features are, A first sidewall (230) is axially provided on one side of the inner ring (210) and the outer ring (220), and a second sidewall (240) is axially provided on the other side of the inner ring (210) and the outer ring (220), the second sidewall (240) being opposite to the first sidewall (230).

3. The rotary joint according to claim 2, Its features are, The inner ring (210) is mounted to the first sidewall (230), and the outer ring (220) is mounted to the second sidewall (240). A first gap is formed between the inner ring (210) and the second sidewall (240), and A second gap is formed between the outer ring (220) and the first sidewall (230).

4. The rotary joint according to claim 2, Its features are, One of the inner ring (210) or the outer ring (220) is mounted to the first sidewall (230) and the second sidewall (240), thereby forming a gap at each side of the other of the outer ring (220) or the inner ring (210) relative to the first sidewall (230) and the second sidewall (240), or The outer ring (220) is mounted to the first sidewall (230) and the second sidewall (240), thereby forming a gap between each side of the inner ring (210) and the first sidewall (230) and the second sidewall (240).

5. The rotary joint according to claim 3 or 4, Its features are, At least one of the gaps is bridged by at least a sliding contact, a gasket, a seal, or an overlap that provides capacitive coupling.

6. The rotary joint according to claim 2, Its features are, The first sidewall (230) and / or the second sidewall (240) are disc-shaped and have a central hole.

7. The rotary joint according to claim 1, Its features are, The annular channel (200) surrounds the hollow cylindrical volume.

8. The rotary joint according to claim 2, Its features are, At least one of the inner ring (210), the outer ring (220), and / or the first sidewall (230) and the second sidewall (240). It is an electromagnetic reflective material, or Having a conductive surface, or It is a dielectric material with a high dielectric constant.

9. The rotary joint according to claim 8, wherein the electromagnetic reflection material is a conductive material.

10. The rotary joint according to claim 2, Its features are, At least one of the first sidewall (230) and the second sidewall (240) contains an absorbing material and / or a reflective material for microwave signals, or A combination comprising absorbent materials, said absorbent materials being mounted on a conductive surface.

11. The rotary joint according to claim 1, Its features are, The inner antenna (211) and / or the outer antenna (221) have adjustable directivity, wherein at least the angle of radiation can be configured to a predetermined value or a position-dependent value.

12. The rotary joint according to claim 1, Its features are, The antenna directivity is optimized to a beam, which has a first reflection at the outer ring (220) opposite the inner antenna (211) and a second reflection at the inner ring (210); or The antenna directivity is optimized to a beam that has a first reflection at the inner ring (210) opposite the outer antenna (221) and a second reflection at the outer ring (220).

13. The rotary joint according to claim 1, Its features are, The inner antenna (211) and / or the outer antenna (221) have adjustable directivity, wherein the transmit power and receiver sensitivity, together with the conductivity of the reflective surfaces of the inner and outer rings, can be configured for a predetermined number of reflections between the inner ring (210) and the outer ring (220).

14. The rotary joint according to claim 1, Its features are, The inner antenna (211) and the outer antenna (221) are axially displaced from each other, and / or The inner ring (210) and / or the outer ring (220) have attenuating material, which is axially fixed to the transmitting antenna and the receiving antenna, and / or The inner antenna (211) and / or the outer antenna (221) are guided into the channel (200), and / or The inner antenna (211) is guided toward the outer ring (220), and / or The outer antenna (221) is directed toward the inner ring (210).

15. The rotary joint according to claim 2, Its features are, The annular channel (200) defines a width (251) between the first sidewall (230) and the second sidewall (240), wherein, At least one wavelength of the microwave signal (169) is shorter than twice the width (251), and The at least one wavelength of the microwave signal (169) can be shorter than 1 / 3, 1 / 4, 1 / 5, or 1 / 10, or 1 / 20, or 1 / 50 or 1 / 100 of the width (251).

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