Rotary joint with dielectric waveguide

A contactless datalink for transmission of data between a rotatable part and a stationary part, including a dielectric waveguide split into two sections. A first dielectric waveguide section is at the rotatable part and a second dielectric waveguide section is at the stationary part. The first dielectric waveguide section is coupled to a transmitter and the second dielectric waveguide section is coupled to a receiver.

BACKGROUND

1. Field of the Invention

The invention relates to high speed datalinks for non-contacting or contactless signal and data transmission, in particular to rotating transmission devices such as rotary joints. Such transmission devices may be used in computer tomography scanners, also called CT scanners. These datalinks may be used in a mm-wave range.

2. Description of Relevant Art

Contactless rotatable couplers, also called contactless rotary joints, are used to couple signals and data between parts rotatable against each other. For example, in CT scanners, a rotating x-ray tube and an x-ray detector generate high-speed imaging data. The data may be transmitted from the rotating part to the stationary part. Furthermore, control signals for controlling the device and, specifically, the power supply of the x-ray tube may be transmitted from the stationary to the rotating part and vice versa. Many further applications exist, where there is the need to transmit control signals or data between a rotor and a stator—for example in windmills, revolving transfer machines, bottling plants, packaging machines or placement heads of insertion machines.

A capacitive rotary joint for CT scanners is disclosed in U.S. Pat. No. 5,600,697. A large diameter rotating ring carries a differentially driven strip line guiding a signal along this circumference of the ring. The strip line has copper conductors on a PCB base. This strip line has a bandwidth limited to a few GHz and therefore a data rate limited to a few Gbit/s.

A dielectric cable is disclosed in US 2008/036558 A1. A hybrid plastic waveguide is disclosed in EP 3203287 A1. A dielectric waveguide using powdered material is disclosed in US 448004350. A tiltable waveguide member using a ball and socket configuration is disclosed in U.S. Pat. No. 9,871,283 B1. DE 102015105657 A1 discloses a connector for dielectric waveguides.

EP1729646 discloses a datalink based on a dielectric waveguide. The couplers for coupling signals into and out of the waveguide are comparatively complex. EP 3309898 A1 discloses an antenna module for millimeter-wave communication which combines transmit and receive signals to a transceiver and couples them into a dielectric waveguide by an antenna.

SUMMARY

The embodiments are providing a contactless datalink for transmission of data between rotating parts in a millimeter waveband. The device may be simple, easy to install, easy to maintain and cost-efficient.

In an embodiment, a contactless datalink configured to transmit data between a rotatable part and a stationary part includes a ring-shaped dielectric waveguide that is split into two components, preferably two identical and/or symmetrical components and forming a disc configuration. One component, for example a first component, may be mounted at the stationary part of a device, and a second component may be mounted at the rotatable part. The dielectric waveguide may have a round cross section, or an oval cross-section, or a rectangular cross section. In an embodiment, the rotatable and stationary parts may be exchanged (in that a rotatable part can be configured to be stationary, while a stationary part can be configured to be rotatable). Preferably, there is a gap between the two components in a plane that is transverse—and preferably orthogonal—to the rotation axis, which axis forms the center of rotation. In another embodiment, the ring may be split cylindrically and parallel to the rotation axis to form a drum configuration. Any configuration allows coupling of signals from either side to the other side. The ring-shaped dielectric waveguide preferably has a center axis substantially aligned with the axis of rotation between the rotatable and the stationary part. Here the term of identical and/or symmetrical components preferably relates to the structure of these components, for example cross section or ring diameter. They may include different sections as disclosed herein.

The width of the gap is preferably dimensioned in the range of 1/10th to ⅙th of a wavelength (of a signal transmitted through the dielectric waveguide) in air and may have any size between nearly zero and ¼th of a wavelength in air. There may be changes and variations in this dimensional range—for example, caused by mechanical tolerances. Later, reference will be made to these waveguide components as waveguides.

The dielectric waveguide may have a cladding including a dielectric with lower dielectric constant than that of the core. The core of the dielectric waveguide may have a round cross-section, or an oval cross-section, or a rectangular crossssection.

The split waveguide preferably is held by a mechanical support or cladding that has a lower dielectric constant than that of the waveguide itself, and which mechanical support may include, for example, a plastic foam or a different material.

The waveguide preferably has a low dielectric constant and low losses in the frequency range at and above 60 GHz (Millimeter-Wave range, which is defined as having a wavelength between 1 mm and 10 mm, which corresponds to a frequency range of 30 GHz to 300 GHz. This frequency band is called EHF or Extremely High Frequency band). Preferred materials are plastics with a low relative dielectric constant (1.5 to 3.5) and low losses, for example Polytetrafluorethylene (PTFE) and (PP) Polypropylene, Polyethylene or Polystyrene, chlorinated Polyethylene (CPE), Polyether ether ketone (PEEK), Polyphenylene sulfide (PPS), Cyclo-olefin polymer (COP) or Polyimide or combinations thereof. In one embodiment, the waveguide is made from solid plastic. It may also be filled with ceramics or made as foam to adjust the dielectric constant.

In one embodiment, which may be based on a waveguide structure as described above, a stationary waveguide (or a waveguide component) forming a circle with two waveguide sections, preferably both located in a plane transverse to the axis of rotation, and around the axis of rotation, is split in two sections that preferably have the same length. A second waveguide component at the second part—which may be the rotatable part of the device—includes also a first section and a second section. Preferably, such second, rotatable waveguide component is substantially symmetrical with respect to the first waveguide component, and mounted close to the first waveguide component to form a narrow gap therebetween. The stationary waveguide component and the rotatable waveguide component are in close proximity with each other such that signals are coupled between the stationary and rotatable waveguides, preferably in both directions—from the stationary waveguide component to the rotatable waveguide component and from the rotatable waveguide component to the stationary waveguide component. Preferably all waveguide sections have approximately equal lengths, and therefore each waveguide section—whether a waveguide section of the first, stationary waveguide or a wavesection of the second, rotatable waveguide—covers about half the circumference of their part, corresponding to an angle of approximately 180 degrees. The first stationary waveguide section and the second stationary waveguide section are connected with their two ends (that are located close together) to a 3 dB coupler, which is further coupled to a receiver. The 3 dB coupler combines the signals from both stationary waveguide sections and forwards these to the receiver. At the opposing ends of the first stationary waveguide section and the second stationary waveguide section, there may be coupled the absorbers. Similarly, the rotatable waveguide sections are connected with their ends (that are located close together) to a corresponding 3 dB coupler, which is further connected to a transmitter. The signals from the transmitter are forwarded to the 3 dB coupler, which splits a given signal into two equal signals that are then fed into the corresponding rotatable waveguide sections. The opposing ends of the rotatable waveguide sections may also be terminated by respective absorbers.

In a related embodiment, the stationary waveguide sections are connected at positions close to each other with a transmitter and a receiver, such that the first stationary waveguide section is connected to receiver, and the second stationary waveguide section is connected to a transmitter. The first rotatable section is connected at a first end with a first 3 dB coupler, which is further connected to a receiver. The second end is connected to a second 3 dB coupler which is further connected to a transmitter. Further, as viewed in a clockwise direction around the waveguide structure, the first end of the second rotatable waveguide section is connected to the first 3 dB coupler, whereas the second end of the second rotatable waveguide is connected to the second 3 dB coupler. This configuration allows for signal transmission without change in phase. The angular gap prevents cross-coupling. The term of “close to” may refer to the ends of dielectric waveguide sections that are in proximity to each other.

In a further embodiment, several substantially identical or different of the above described embodiments might be installed in parallel or antiparallel to increase the data transmission capacity in a given application.

In yet another embodiment, the dielectric waveguide is configured as a closed loop. Such loop may have a circular shape and be configured as one, single unitary part, or have an alternative structure in which both ends are glued or welded together. This circular dielectric waveguide might be fixed to the stator (thus becoming a stationary waveguide) or to the rotor (and be a rotatable waveguide). The cross-section of the waveguide may be circular, elliptic, oval, or rectangular, or have any other shape appropriately suited to guide a chosen wave. In an embodiment, this waveguide may be substantially identical to one waveguide section as described above. Whether the waveguide includes a single section of is split into two sections extended along one another, each of the sections that are present is configured to guide a wave and/or the two sections “split” from one another are configured to guide a given wave together, jointly.

There may be at least two couplers configures as sections of dielectric waveguides as described herein. These couplers may be used to couple a wave in and/or out of the closed-loop waveguide. These couplers generally are kept in close distance to one another, preferably dimensioned to have a physical length in the range of ⅙thto 1/10thof a wavelength in air, the distance may be in a range between near zero and up to ¼thof a wavelength (because of mechanical tolarances). The couplers preferably are mounted as circular segments having the same center point as that of the closed loop waveguide. The lengths of the two couplers preferably are substantially identical and are shorter than half of the total circumference of the closed loop.

The closed-loop waveguide may also be configured to rotate at a different speed than that of the rotatable coupler. Since depending on the specific of a given configuration the closed-loop waveguide can be made either rotatable or stationary, one of the couplers may be mounted in a fixed position and at a fixed distance to the closed-loop waveguide. The rotatable coupler may be mounted in such a way that it cannot collide with the stationary coupler during the rotation (in other words, mounting configuration for the rotatable coupler prevents the collision between the rotatable copler and the stationary coupler during the operation of the device). This means that one of the two couplers (e.g. the stationary coupler) may be mounted on the inner side of the waveguide, while the other coupler (e.g. the rotatable coupler)—on the outer side. Alternatively, the couplers may be mounted in front of or behind the closed-loop waveguide or at any angular position where a collision between them is avoided.

The stationary couplers may have the same lengths and/or the rotatable couplers may have the same lengths. Additionally or in the alternative, the stationary couplers may have the same lengths as those of the rotatable couplers.

One or both of the couplers may also be part of a waveguide section as described above. That means that the coupler is formed of a part of the other section of a waveguide that is split into two sections, where either of the section can guide a wave but also the combination of the two sections is configured to guide the wave. Preferably, this is the rotatable coupler when the closed loop waveguide is stationary.

The transceivers of the embodiments may include a transmitter and receiver that are connected to one port of the transceiver for wireless transmission and reception of the signals. This port can also be used for “wired” communication through a dielectric waveguide, if the port is coupled to a dielectric waveguide configured to guide the wave of choice. The stationary transceiver has one port to transmit and receive signals wirelessly and is connected to the stationary coupler either by a connecting dielectric waveguide or by directly coupling a wave into the coupler e.g. by an antenna. Just as the stationary transceiver, the rotatable transceiver may also have one port to transmit and receive signals wirelessly, and is connected to the stationary coupler. The waveguide and couplers (which are also formed of waveguide elements as described) are in close contact which each other such that signals are coupled between the stationary and rotatable coupler with the waveguide in between, and preferably in both coupling directions.

In one example, data transmitted up (from the stationary transceiver to the rotary or rotational transceiver) are propagating as waves in the waveguide in a clockwise direction, the data transmitted down (from the rotary transceiver to the stationary transceiver) are propagating in the contrary direction. Preferably, the closed-loop waveguide has an attenuation low enough to allow communication between the both transceivers during a first round of the waves travelling but high enough not to distort the receiver after the first round is completed.

Pairs of couplers may be connected to the transceivers either at ends that are close to each other or at ends that are distant and separated by the length of the couplers.

In another embodiment with transceivers offering more than one RF (Radio Frequency) port, multiple parallel communications can be increased by employing more than one closed-loop waveguide with rotatable and stationary couplers that are connected to the ports of one or more transceivers.

Preferably, the stationary transceiver generates and modulates RF (Radio Frequency) signals in the range of and above 60 GHz and couples a wave into the dielectric waveguide, where it propagates towards the stationary transceiver and vice versa. The technology can also be used with waves at substantially all carrier frequencies that can be coupled into dielectric waveguides, e.g. operating at 2.4 GHz or 5 GHz or any frequency above that (but below optical frequencies).

Preferably, the transceivers are employing the MIMO (multiple in-multiple out) technology as e.g. defined in recent substandards of IEEE-802.11-(WiFi/WLAN-Standard) e.g. IEEE-802.11n—and newer substandards-(WiFi/WLAN-Standard). Another implementation is configured according to a widely used commercial standard such as LTE, at e.g. 2.6 GHz. These standards for wireless communication optimize the operation of embodiments of the device by allowing any port of one transceiver to communicate with any port of the corresponding transceiver, thereby facilitating the increase of the data rate by multiple parallel communications. Both transceivers may have a another wired port, which is electrically coupled to transmit and receive data via a bus. The closed-loop waveguide and the couplers form a contactless rotary joint for bidirectional data transmission. In case of the CT gantry, data obtained by an X-Ray detector is transmitted via the rotatable transceiver through the contactless rotary joint to the stationary transceiver which is connected by bus to a stationary evaluation unit.

In at least one embodiment, the at least one rotatable transceiver has at least one RF port that separately optimizes transmission quality and/or data rate by controlling carrier frequency, phase, amplitude and modulation parameters of each port separately to establish a communication to any one or more RF ports of the stationary transceiver to separately match changing attenuation and phase during the rotation and to avoid crosstalk between the RF ports of the same transceiver.

Alternatively or in addition, and In a related embodiment, the at least one rotatable transceiver has two or more RF port that separately optimize transmission quality and/or data rate by controlling carrier frequency, phase, amplitude and modulation parameters of each port separately to any two or more RF ports of the stationary transceiver to separately match changing attenuation and phase during the rotation and to avoid crosstalk between the RF ports of the same transceiver and to establish multiple parallel communication channels during all times.

In yet another non-exclusive embodiment, a contactless datalink is configured to operate at an operating frequency within the EHF band. It may also be configured to operate at an operating frequency between 2.4 GHz and 30 GHz.

There are further embodiments having different combinations of waveguides, waveguide sections, transmitters and receivers. Examples of these embodiments are described in reference to the drawings in more detail.

Generally, the drawings are not to scale. Like elements and components are referred to by like labels and numerals. For the simplicity of illustrations, not all elements and components depicted and labeled in one drawing are necessarily labels in another drawing even if these elements and components appear in such other drawing.

While various modifications and alternative forms, of implementation of the idea of the invention are within the scope of the invention, specific embodiments thereof are shown by way of example in the drawings and are described below in detail. It should be understood, however, that the drawings and related detailed description are not intended to limit the implementation of the idea of the invention to the particular form disclosed in this application, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG.1aillustrates a first embodiment of the waveguide structure, showing a portion of the dielectric waveguide100. The dielectric waveguide100includes two waveguide components, preferably two identical and/or symmetrically-disposed components101and102, forming a disc configuration. One component, for example, a first component101is mounted at the stationary part of the device, and a second component102is mounted at the rotatable part. The dielectric waveguide components may together (when considered combined) form a substantially round cross-section (as shown inFIG.1a), or an oval or rectangular cross-section in the alternative. Notably, in an embodiment the rotatable and stationary parts to which the components1-2.102are mounted may be exchanged. There is generally left a gap107between the two components along a plane109that may be orthogonal to the rotation axis108.

As shown inFIG.1b, in a related embodiment of the waveguide structure, the ring waveguide including a first dielectric waveguide component103and a second dielectric waveguide component104may be formed such that the gap between these waveguide components103,104is formed in a plane that, while being transverse to the rotation axis108, is not exactly perpendicular to the axis108(as shown, the plane of the gap intersects the axis108at an angle, such as a slanted angle or a 45 degrees angle). In another embodiment, the ring including a first dielectric waveguide component105and a second dielectric waveguide component106may be split into two waveguide components106,107(that is, formed by these two component) as shown in FIG.1calong a cylindrical surface substantially parallel to the rotation axis to thereby form a drum configuration.

Any of the above-presented configurations allows for coupling of signals from either side to the other side.

InFIG.2, a basic embodiment of the waveguide-containing portion of the device is shown, which may be based on a waveguide structure of the first embodiment ofFIG.1a. Here, a stationary waveguide (131,132) including a first section131and a second section132is at a first part of the device. The rotatable waveguide of the device—the waveguide (133,134)—also has a corresponding first section133and a corresponding second section134. The stationary waveguide and the rotatable waveguide of the embodiment ofFIG.2are in close contact with each other such that signals are easily coupled between the stationary and rotatable waveguides (131,132) and (133,134), preferably in both directions—from the stationary waveguide to the rotatable waveguide and from the rotatable waveguides to the stationary waveguides. Preferably, all waveguide sections131,132,133,134have approximately the same lengths, and therefore cover about half the circumference of the corresponding rotational or stationary part, corresponding to an angular extent of approximately 180 degrees. The waveguide sections preferably have two ends. The first stationary waveguide section131and the second stationary waveguide section132are connected with their two ends that are close together (neighboring each other) to a 3 dB coupler142, which is further coupled to a receiver141. The coupler142is configured to combine, in operation, the signals from both stationary waveguide sections121,132and forward these to the receiver141. The opposing ends of the waveguide sections131,132are coupled to absorbers143and144. The rotatable waveguide sections133and134are connected with their ends that are close together to a 3 dB coupler152, which is further connected to a transmitter151. In operation, the signal from the transmitter151are forwarded to the 3 dB coupler152, which splits such signal into two substantially equal signals that are then fed into each of the rotatable waveguide sections133and134. The opposing ends of the rotatable waveguide sections are also terminated by absorbers153and154.

Preferably, the transmitter151is configured to generate and modulate RF signals in the range of and above 60 GHz, and to couple a wave at such frequency(ies) into the dielectric waveguide, where the wave propagates towards the receiver141.

InFIG.3, a related embodiment is schematically shown. Here, the curved stationary waveguide sections131and132are connected (at positions close to each other) with a transmitter164and a receiver161, such that the first stationary waveguide section131is connected to the receiver161, and the second stationary waveguide section132is connected to the transmitter164. The first rotatable waveguide section133, on the other hand, is connected at uts first end with a first 3 dB coupler172, which is further connected to a receiver171. The second end of the waveguide section133is connected to a second 3 dB coupler174, which is further connected to a transmitter173. Further, viewed in a clockwise direction, the first end of the second rotatable waveguide section134is connected to the first 3 dB coupler172, whereas the second end of the second rotatable waveguide134is connected to the second 3 dB coupler174. This criss-cross connection allows for a signal transmission without change in phase. The angular gap between the ends of line prevents cross-coupling between the ends of the rotatable waveguide sections133and134.

InFIG.4, yet another related embodiment is shown with only one first waveguide131and one second waveguide133. The first waveguide131is connected at one end to a receiver182and at the opposing end to a transmitter181. The second waveguide133is connected at a first to a receiver192and at the opposing end to a transmitter191. The link is structured such that transmitter and receiver are arranged opposite to one another as far as the directions of propagations of the signals is concerned. A spatial gap between receiver and transmitter causes a high signal attenuation between receiver and transmitter.

Alternatively, and in a related embodiment, to arrive at a configuration somewhat similar to that ofFIG.4, the ends of the two stationary waveguide sections (each covering approximately half of the circumference of the stationary part of the device) can be joined to a single waveguide131, the free ends of which are then connected to the transceiver combining receiver182and transmitter181, respectively. At the same time, the ends of the two rotatable waveguide sections (each covering approximately half of the circumference of the rotatable part o the device) can be joined to a single waveguide133, the free ends of which are then connected to the transceiver combining receiver192and transmitter191.

InFIG.5, a further embodiment is shown, where the stationary waveguide includes a first stationary waveguide section131and a second stationary waveguide section132(which have substantially the same lengths and therefore have an angular extend of about 180 degrees each). The rotatable waveguide includes a first rotatable waveguide section133, a second rotatable waveguide section134, and a third rotatable waveguide section135(which all have about the same size, and therefore cover corresponding angles of about 120 degrees). The first stationary waveguide section131is connected at a first end to a receiver201and to a transmitter202at the opposing end. As viewed clockwise next to this end, the first end of the second stationary waveguide section132is connected to a receiver203, and the opposing end to a transmitter204. Therefore, transmitters and receivers present in this embodiment are alternatingly connected at the ends of the sections of the first stationary waveguide, such that a receiver is followed by a transmitter in a clockwise view. At the rotatable waveguide sections133,134,15, there is basically the same arrangement, such that a transmitter is followed by a receiver in a clockwise view on each of the three sections. Therefore, the first rotatable waveguide section133has a receiver211at a first end thereof and opposing thereto a transmitter212. Next to it, the second rotatable waveguide section134has a receiver213at its first end and a transmitter214at its second end. This is followed by the third rotatable waveguide section having a receiver215at its first end and a transmitter216at its second end. The second end of the third rotatable waveguide section135with the transmitter216is disposed close to the first end of the first rotatable waveguide section133with the receiver211. In a related embodiment, the sequence of transmitters and receivers may be reversed.

Also, one end of the first stationary waveguide section131and132can be joined together to form a single (loop) waveguide connected, on one hand, to a transceiver device that combines the receiver203and the transmitter202, on the other hand, to another transceiver device combining the receiver201and the transmitter204. Also, receiver213and transmitter212, receiver215and transmitter214and receiver211and transmitter216can be paired to transceivers.

InFIG.6, a further embodiment is shown. A first part, for example the stationary part, may bear stationary waveguide sections131,132. A second part, for example a rotatable part, may bear rotating waveguide sections133,134,135,136which all have about the same size, and therefore cover angles of about 90 degrees each. The stationary waveguides131,132have receivers112,114at their first ends and transmitters111,113at their second ends. Accordingly, in the clockwise direction, first waveguide131has a receiver114at its first end and a transmitter111at its second end, whereas the first waveguide132has a receiver112at its first end and a transmitter113at its second end.

Each of the rotatable waveguides have either a transmitter or a receiver at one end, and an absorber at the opposing end. Here, the first rotatable waveguide133is show to have, as viewed in a clockwise direction, at its first end a receiver121and an absorber122opposing thereto. The second rotatable waveguide section134has an absorber123at an end close to the absorber122and a transmitter124opposing thereto. The third rotatable waveguide section135has a receiver125close to the transmitter124and opposing thereto an absorber126. The fourth rotatable waveguide section136has an absorber127close to the absorber1226and opposing thereto a transmitter128.

The function and, therefore, positioning of the rotatable and the stationary parts may be exchanged. Furthermore, the orientation of the transmitters or receivers may be exchanged with respect to the waveguides. In any case, in each of the embodiments, each of the transmitters may be exchanged by a receiver, and each of the receivers may be exchanged by a transmitter.

All transmitters and receivers shown inFIGS.4,5, and6as well as receiver161and transmitter164inFIG.3may be combined to a transceiver when both half waveguides are combined to a full waveguide in direct vicinity of the transceivers.

InFIG.7, a basic concept of a further dielectric waveguide embodiment300is shown in a sectional view. The waveguide has a dielectric core301and a metallic shield302, which has a gap303. For coupling a signal, there may be a pickup310that preferably has only a short length of few millimeters or few centimeters (as compared to the total length of the dielectric waveguide, which may be in the range of several meters). The embodiment is configured to ensure that energy may only be radiated out of the gap at a position where the pickup is located, as there the impedance should be matched.

FIG.8shows schematically a CT (Computed Tomography) scanner gantry. The stationary part is suspended within and is part of a massive frame810. The rotatable part809of the gantry is rotatably mounted with respect to the stationary part and rotates along the rotation direction808. It supports an X-ray tube801for generating an X-ray beam802that radiates through a patient804lying on a table807and which is intercepted by a detector803and converted to electrical signals and imaging data thereof. Electrical power from power supply unit811may be transmitted by a slipring (not shown) to the rotatable part. The data obtained by the detector803are transmitted via contactless rotary joint800to an evaluation unit806by means of a data bus or network805.

In the following description ofFIGS.9,10,11, the closed-loop dielectric waveguide400is considered, but referred to as “waveguide400” of “waveguide structure400”, for simplicity of presentation.

InFIG.9, an embodiment is shown which may be based on a standard dielectric waveguide structure400that is dimensioned to form a closed loop and that includes one part that is conformed to a circle (where either both ends of the waveguide are glued or welded together or where such waveguide is initially configured as a circular loop, as one part). This circular dielectric waveguide might be fixed to the stator (stationary part) or fixed to the rotor (rotatable part). The cross-section of the waveguide400might be shaped circularly, ellipticly, as an oval, or rectangularly, or\have any other shape suited to guide a target wave.

Also, this waveguide400might be substantially identical to one waveguide section101as described inFIG.1, that means it is only one section of a dielectric waveguide split into two sections where either section can guide a wave but also the combined sections.

Two couplers (420,440) formed of a standard dielectric waveguide as described may be used to couple a wave in and/or out of the waveguide400. These couplers are kept in close distance preferably in the range of ⅙thto 1/10thof a wavelength in air, the distance may vary because of mechanical tolerances between near zero and up to ¼thof a wavelength. The couplers preferably are mounted as circular segments having the same center point as the waveguide400. The lengths of each of the two couplers preferably are substantially identical and are shorter than half of the total circumference.

The waveguide400might also be configured to rotate at a different speed than that of the rotatable coupler. Since in an embodiment, the waveguide400is configured as either rotatable or stationary waveguide, one of the couplers might be mounted in a fixed position and distance to the waveguide400. The rotatable coupler440is mounted in such a way that it cannot collide with the stationary coupler during rotation. This means that one coupler (e.g. the stationary coupler420as in this figure) can be mounted on the inner side of the waveguide400, the other coupler (e.g. the rotatable coupler440as in this Figure) on the outer diameter. Alternatively, the couplers can be mounted before or behind the waveguide400or at any angular disposition where a collision is avoided.

One or both of the couplers420,440can also be part of a waveguide section102as described inFIG.1, that means that the coupler is formed of a part of the other section of a waveguide split into two sections where either section can guide a wave but also the combined sections. Preferably this is the rotatable coupler440when the waveguide400is stationary.

The transceivers410,430include a transmitter and receiver that are connected to one port of the transceiver for wireless transmission and reception of. This port can also be used for “wired” communication through a dielectric waveguide if the port is coupled to a dielectric waveguide capable to guide the wave. The stationary transceiver410having one port to transmit and receive signals wireless and is connected to the stationary coupler420either by a connecting dielectric waveguide or by directly coupling a wave into the coupler e.g. by an antennaor by a coaxial cable connecting the transceiver to an antenna which then couples the signal into the coupler. The stationary transceiver410has one port to transmit and receive signals wirelessly and is connected to the stationary coupler420. (Similarly, the rotatable transceiver430has one port to transmit and receive signals wirelessly and is connect to the rotatable coupler440.) The waveguide400and couplers420,440that are also formed of waveguides as described, are in close contact with each other such that signals are operably coupled between the stationary and rotatable couplers with the waveguide400in between, preferably in both directions.

In the configuration described in thisFIG.9data transmitted up (from stationary transceiver410to rotary transceiver430) are propagating as waves in the waveguide400in clockwise direction, the data transmitted down (from rotary transceiver430to stationary transceiver410) are propagating in the counter-clockwise direction. Preferably the waveguide400has an attenuation low enough to allow communication between the both transceivers during a first round of the waves travelling but high enough not to distort the receiver after the first round is completed

Preferably, the stationary transceiver410generates and modulates RF signals in the range of and above 60 GHz and couples a wave into the dielectric waveguide where it propagates towards the rotary transceiver430and vice versa. The technology can also be used with all carrier frequencies that can be coupled into dielectric waveguides, e.g. operating at 2.4 GHz or 5 GHz or any frequency above that but below optical frequencies.

Both transceivers have a another wired port that is not shown which is electrically coupled to transmit and receive data via a bus. The waveguide400and the couplers410,430form a contactless rotary joint for bidirectional data transmission. In case of the CT gantry shown and described inFIG.8. The data obtained by the detector803ofFIG.8is transmitted via the rotatable transceiver430through the contactless rotary joint described inFIG.9to the stationary transceiver which is connected by bus (not shown) to the stationary evaluation unit806ofFIG.8where the data are received, control data are transmitted in the opposite direction.

FIG.10illustrates the same principle setup of rotatable couplers and waveguide400as inFIG.9. The difference between the embodiments ofFIG.10andFIG.9is that inFIG.10a multiport transceiver411with at least a first stationary port412and at least a second stationary port413is configured to optimize transmission quality and/or data rate by controlling carrier frequency, phase, amplitude and modulation parameters of each of these RF porst to separately match changing attenuation and phase during the rotation and to avoid crosstalk between the channels of the transceiver411; and a multiport transceiver431with at least a first rotatable port432and at least a second rotatable port433is configured to optimize transmission quality and/or data rate by controlling carrier frequency, phase, amplitude and modulation parameters of each of these RF ports to separately match changing attenuation and phase during the rotation and to avoid crosstalk between the channels of the transceiver431.

In the configuration described data transmitted up (from stationary multiport transceiver411to rotary/rotatable multiport transceiver431) are propagating as modulated waves in the waveguide in clockwise direction, the data transmitted down (from rotary multiport transceiver431to stationary transceiver411) are propagating in the contrary direction. Preferably the waveguide400has an attenuation low enough to allow communication between the both transceivers during a first half round of the waves travelling but high enough not to distort the receiver after the first round is completed

In this configuration, the first stationary port412and the second stationary port413of the stationary multiport transceiver411communicate via first stationary coupler421, second stationary coupler422, waveguide400and first rotatable coupler441, second rotatable coupler442with the first rotatable port432and the second rotatable port433of the rotatable multiport transceiver431. The transceivers select as inputs the RF port with the best communication quality, which changes during rotation, typically determined by bit error rate. To optimize the transmission by lowering the crosstalk between the channels the first and second rotatable couplers441,442may be positioned approximately 180 degrees apart of each other. The same applies for the first and second rotatable couplers441,442which preferably are positioned approximately 180 degrees apart of each other. With n (n=1, 2, 3, 4, 5, . . . ) ports the displacement of the couplers should be approximately 360 degrees divided by n.FIG.10shows a displacement of approximately 90 degrees. Here, the stationary waveguide couplers421,422are shown connected to the stationary transceiver411and the ends of these two couplers that are separated from one another at least by a length of one of these two couplers. Similarly the rotatable waveguide couplers441,442are shown connected to the rotatable transceiver431at the ends of these two couplers that are separated from one another at least by a length of one of these two couplers.

Preferably the transceivers are employing the MIMO (multiple in-multiple out) technology as e.g. defined in recent substandards of IEEE-802.11-(WiFi/WLAN-Standard) e.g. IEEE-802.11n and newer substandards-(WiFi/WLAN-Standard). Another implementation into a widely used commercial standard is LTE at e.g. 2.6 GHz. These standards for wireless communication optimize by allowing any port of one transceiver to communicate with any port of the corresponding transceiver.FIG.11is similar toFIG.10.

In the configuration port the first stationary port412of the stationary multiport transceiver411communicates via stationary coupler421, waveguide400and rotatable coupler441with port the first rotatable port432of the rotatable multiport transceiver431, the second stationary port413of the stationary multiport transceiver411communicates via stationary coupler421, waveguide400and rotatable coupler441with the second rotatable port433of the rotatable multiport transceiver431.

Here preferably the closed loop waveguide400has an attenuation low enough to allow communication between the both transceivers during a first half round of the waves travelling but high enough not to distort the receiver after the first round is completed. To optimize the transmission the first and second rotatable couplers441,442may be positioned approximately 180 degrees apart of each other. The same applies for the first and second rotatable couplers441,442which may be positioned approximately 180 degrees apart of each other. With n (n=1, 2, 3, 4, 5, . . . ) ports the displacement of the couplers should be approximately 360 degrees divided by n.FIG.11shows a displacement of approximately 90 degrees. Here, the stationary waveguide couplers421,422are shown connected to the stationary transceiver411and the ends of these two couplers that are located close to one another. Similarly the rotatable waveguide couplers441,442are shown connected to the rotatable transceiver431at the ends of these two couplers that are located close to one another.

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