Rotary Transmission System Using a Waveguide

Abstract

A coupler provides a high speed datalink between rotatable parts, which includes comprising a circular gap shaped as a hollow-cylindric volume and at least two antennae. The gap is formed between a first ring and a second ring rotatable against the first ring. A first antenna is mechanically coupled to the first ring and a second antenna is mechanically coupled to the second ring. The antennae are configured to effectuate a microwave signal connection between them the antennae based on multiple reflections of the signal at the rings.

Claims

1. A high speed datalink rotary joint comprising: a first ring with a first diameter and a second ring with a second diameter that is larger than the first diameter, the first ring being coaxially arranged to the second ring and around a center axis to form a gap between the rings, the first ring and the second ring comprising at least partially conductive material, the rotary joint further comprising a first antenna and a second antenna rotatable relative to the first antenna, the first antenna being directed into the gap in a first direction and at a first angle, the second antenna being directed into the gap in a second direction opposing the first direction and at a second angle (332), and wherein each of the first angle (331) and the second angle is defined relative to a radial direction of the center axis and has an absolute value in a range from 0 to 90, wherein each of values of the first angle and the second angle is a fixed value and remains over rotation.

2. A rotary joint according to claim 1, wherein no sidewalls are provided between the first ring and the second ring.

3. A rotary joint according to claim 1, wherein the gap has a rectangular cross section.

4. A rotary joint according to claim 1, wherein the gap has a width and a height that corresponds to a radial distance between the first ring and the second ring, wherein each of the height and the width is larger than two times a wavelength of a signal having the lowest frequency of signals to be transmitted by the first antenna and/or the second antenna.

5. A rotary joint according to claim 1, wherein an absolute value of the first angle is equal to an absolute value of the second angle.

6. A rotary joint according to claim 1, wherein the first antenna and the second antenna are axially displaced from one another.

7. A rotary joint according to claim 1, wherein the first antenna is mechanically coupled to the first ring and/or the second antenna is mechanically coupled to the second ring.

8. A rotary joint according to claim 1, wherein each of the first antenna and the second antenna has a corresponding radiation pattern that is constant over rotation.

9. A rotary joint according to claim 1, wherein each of the first antenna and the second antenna is configured for a microwave or millimeter wave signal connection.

10. A rotary joint according to claim 1, wherein an absolute value of the first angle is larger than a width of the beam of the first antenna measured at a half-power level and/or an absolute value of the second angle is larger than a width of a beam of the second antenna measured at a half-power level.

11. A rotary joint according to claim 1, wherein the first antenna is electrically coupled to a transmitter and the second antenna is electrically coupled to a receiver, or the first antenna is electrically coupled to the receiver and the second antenna is electrically coupled to the transmitter, or the first antenna is electrically coupled to a first transceiver and the second antenna is electrically coupled to a second transceiver.

12. A rotary joint according to claim 13, wherein each of the transmitter, the receiver, and first and second transceivers is configured for OFDM or single carrier with frequency domain equalization.

13. A rotary joint according to claim 1, wherein at least one of the first antenna and the second antenna includes a phased array and/or a horn antenna.

14. A rotary joint according to claim 1, wherein at least one of the first antenna and the second antenna is mounted flush to a surface of at least one of the first ring and the second ring.

15. A rotary joint according to claim 1, wherein at least one of the first and second rings includes an electromagnetically reflective material or includes a dielectric material with high permittivity.

16. A rotary joint according to claim 3, wherein the gap has a hollow cylindrical volume.

17. A rotary joint according to claim 9, wherein the first ring and the second ring are configured to alternatively reflect the microwave or millimeter wave signal.

18. A rotary joint according to claim 13, wherein, wherein the at least of the first antenna and the second antenna has a directivity of at least 5 dBi.

19. A rotary joint according to claim 14, configured to divert a main beam of the at least one of the first antenna and the second antenna electronically or with a reflector.

20. A rotary joint according to claim 15, wherein the electromagnetically reflective material includes an electrically conducting material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In the following the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment with reference to the drawings.

[0049] FIG. 1 shows an embodiment.

[0050] FIG. 2 shows a sectional side view of the circular gap.

[0051] FIG. 3 shows a sectional side view without sidewalls.

[0052] FIG. 4 shows a front view into the circular gap.

[0053] FIG. 5 shows an embodiment with antennas within the gap.

[0054] FIG. 6 shows a further front view into the circular gap.

[0055] FIG. 7 shows a multipath propagation.

[0056] FIG. 8 shows a dual path propagation.

[0057] FIG. 9 shows a linear embodiment.

[0058] FIG. 10 shows an exemplary functional block diagram.

[0059] FIG. 11 shows an exemplary relation of beam with and beam angle.

DETAILED DESCRIPTION

[0060] In FIG. 1, the first embodiment is shown. A gantry 100 of a CT scanner comprises a stationary part 102 and a rotatable part 150 including rotatable disk 104, rotatable about a rotation axis 110. The rotatable disk may hold rotatable components which are not shown here, like a power supply, an X-ray tube, an X-ray detector and a data acquisition system. Further, a slip ring or a rotatable power transformer which is also not shown, may be provided for transfer of power from the stationary to the rotatable part.

[0061] The rotatable part 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 may be on the same axis. The embodiment would also work with offset axes. Both rings may be rotatable against each other. Any one of the rings may be stationary, whereas the other may be rotatable.

[0062] Further, a first sidewall 230 and/or a second sidewall 240 may be provided. Also, at least one of the sidewalls may be part of a gantry 100 of a CT scanner. Each sidewall may be fixed to one of the rings 210, 220. There may also be a low impedance contact between a sidewall and a ring. To the other ring there may be a sidewall-gap, which may be bridged by sliding brushes, a conductive gasket or any other suitable material which may provide a good electrical contact.

[0063] In an embodiment, the ring 210 and both sidewalls 230, 240 may be connected together forming a U-shaped cross section, while ring 220 is rotatable. There may be sidewall-gaps at the sides of the second ring 220 to allow for rotation. There may be any other combination of connected parts which may allow rotation of the rings 210 and 220 with their mechanically coupled antennas 211 and 221 and may form a toroid with rectangular section together with sidewalls.

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

[0065] The rings 210, 220 and the sidewalls 230, 240 comprise an electrically conductive material like a metal and or a material with electrically conductive surfaces.

[0066] A first antenna 211 is rotatable against a second antenna 221. Both antennas are directed into the volume between the rings. The antennas may rotate or be stationary with their rings, the antennas may be mounted to the rings.

[0067] FIG. 2 shows a sectional side view of an embodiment of the rotary joint 200 having sidewalls. The rotary joint may have a rectangular or squared cross section with a width 251 between the sidewalls 230, 240 and a height 252 between the rings 210, 220.

[0068] The rotary joint 200 has an inner space which allows the propagation of electromagnetic waves with a maximum wavelength Amax equals to two times the width 251 or the height 252, whichever is larger.

[0069] Since the sidewalls 230, 240 are not necessary for the function they can be omitted, then the width of the gap may be the smallest width of the rings 210, 220. Such an embodiment is shown in FIG. 3.

[0070] FIG. 3 shows a similar sectional side view as the previous figure, but without sidewalls 230, 240. Here, some radiation energy may be lost through the open sides, but still a significant part of radiation remains guided between the rings.

[0071] FIG. 4 shows a front view into the circular gap 250 with a possible signal path between first antenna 211 and outer antenna 221. The signal may not only be transmitted in a single mode within the circular gap 250, but it may also be reflected at the first ring 210 and or the second ring 220. In this figure, first antenna 211 and outer antenna 221 may have a relative angle (angle of rotation) of about 180 degrees. The first antenna 211 may emit a signal with a first beam 341 under an angle 331 to a radial direction 112. Here, a radial direction is on a line 112 going under a right angle through rotation axis 110. There may be multiple reflections at the rings as shown and dependent of the specific direction of radiation of the antennas. With each reflection the angles of the electromagnetic wave 310 to be reflected and the reflected wave versus a surface of a ring are the same. Such, the first reflection angle at second ring 311 is the same as the second reflection angle at second ring 312 and the first reflection angle at first ring 313 is the same as second reflection angle at first ring 314. The second antenna 221 may receive the signal with a second beam 342 under an angle 332 to a radial direction 112. Here, the sum of reflection angles 311 (or 312) and 332 may be 90, as well as the sum of reflection angles 313 (or 314) and 331. Here, the beam is only indicated by its centerline. In addition to the beam angle which is the angle of maximum radiation level, the antenna beam may be also characterized by the 3 dB or half power beam width. The half power beam width is the angular width (in degrees), of the major beam or lobe of an antenna radiation pattern at which the signal power is half that of its peak value. As antennas are reciprocal, transmit and receive function may be exchanged. Here, the first antenna 211 and second antenna 221 may be at the first ring 210 and the second ring 220. They may be attached at the ring and radiate through a hole in the ring.

[0072] FIG. 5 shows a similar embodiment as in the previous figure. Here first antenna 211 and second antenna 221 are within the gap 250. They may be mounted on different radii and/or displaced in the direction of rotation axis 110. They may be mounted on a support structure outside the gap 250.

[0073] FIG. 6 shows a further front view of the rotary joint 200 into the circular gap 250 between first ring 210 and second ring 220. In this figure, first antenna 211 and second antenna 221 have a relative angle of about 0 degrees, such that they are opposing each other. Here, the electromagnetic wave 310 may directly propagate from first antenna 211 to second antenna 221. During rotation the relative angles between the antennas is constantly changing, the 0 degree position shown here and also other relative angles shown in the other figures are present only for a short time.

[0074] FIG. 7 shows a multipath propagation. In this figure, first antenna 211 and second antenna 221 have a relative angle of about 180 degrees. Here three different multipath propagations 316, 317, 318 are shown. With a small 3 dB beam width the antennas help to minimize dispersion caused by the multiple paths having different propagation times by attenuating paths with even longer or shorter propagation lengths.

[0075] FIG. 8 shows an embodiment having a dual path propagation. In this figure, first antenna 211 and second antenna 221 have a relative angle of about 270 degrees. Here, the electromagnetic wave 310 may propagate clockwise from first antenna 211 to second antenna 221. There may also be a second counterclockwise signal path 315, if the antenna gain at the given beam angles is high enough and the attenuation by the reflections is low enough, the anticlockwise path may contribute to the receive signal. To enable the equalizer of the receiver to compensate the effects caused by the addition of the two signals the guard interval may cover at least one propagation time around the 360 degrees of the rotary joint. The signal along both paths are alternatingly reflected by the first and second ring. Further, both signal paths may be used for bidirectional signal transmission. This example shows a relative angle of about 270 degrees, but two signal paths are basically available through all relative angles between first antenna 211 and second antenna 221.

[0076] FIG. 9 shows a linear embodiment. A hollow gap 400 includes four sidewalls 410, 420, 430, 440, defining a rectangular cross sectioned or square cross sectioned hollow space. A first sidewall 410 is parallel to a second sidewall 420. Further, a first antenna 411 is mechanically coupled to the first sidewall 410 and a second antenna 421 is movable within the linear gap. The second antenna may be mechanically coupled to the second sidewall. The sidewalls 410, 420, 430, 440 include an electrically conductive material like a metal. They may be made from such a material or they may have a conductive surface which 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 basically the same as the circular embodiments disclosed herein, but is linear. The first sidewall 410 corresponds to the first ring 210 and the second sidewall 420 corresponds to the second ring 220. Further, an embodiment may have any shape like a combination of curved sections and/or linear sections.

[0077] FIG. 10 shows an exemplary functional block diagram. A transmitter 161, which may be fed by a data acquisition system providing imaging data sends signals to first antenna 211 which radiates microwave signals 169 into the circular gap 250. These RF signals 169 are received by antenna 221 and forwarded to a receiver 162. Basically, the direction may be reversed. Also a bidirectional communication may be made.

[0078] FIG. 11 shows an exemplary relation of beam with and beam angle. The larger the beam angle is, the larger the beam width that can be set. This relation limits the dispersion caused by multi-path delay spread. The relation is valid for a first antenna shown here, but also applies to a second antenna. Here a first antenna 211 has a first beam width 171 (3 dB width) and a first beam angle 181. In a case, the first antenna has a second beam width 172 which is larger than the first beam width, then the corresponding second beam angle 182 would be larger than the first beam angle 172. Both beam width are defined as 3 dB (half power) beam widths.

LIST OF REFERENCE NUMERALS

[0079] 100 gantry of CT scanner [0080] 102 stationary part [0081] 104 rotatable disk [0082] 110 rotation axis [0083] 112 radial direction [0084] 150 rotatable part [0085] 161 transmitter [0086] 162 receiver [0087] 169 RF signals [0088] 171 first beam width [0089] 172 second beam width [0090] 181 first beam angle [0091] 182 second beam angle [0092] 200 rotary joint [0093] 210 first ring [0094] 211 first antenna [0095] 220 second ring [0096] 221 second antenna [0097] 230 first sidewall [0098] 240 second sidewall [0099] 250 gap [0100] 251 width [0101] 252 height [0102] 310 electromagnetic wave propagation [0103] 311 first reflection angle at second ring [0104] 312 second reflection angle at second ring [0105] 313 first reflection angle at first ring [0106] 314 second reflection angle at first ring [0107] 315 alternate electromagnetic wave propagation [0108] 316 first multipath propagation [0109] 317 second multipath propagation [0110] 318 third multipath propagation [0111] 331 first beam angle [0112] 332 second beam angle [0113] 341 first beam [0114] 342 second beam [0115] 400 hollow gap [0116] 410 first sidewall [0117] 420 second sidewall [0118] 411 first antenna [0119] 420 second sidewall [0120] 421 second antenna [0121] 430 third sidewall [0122] 440 fourth sidewall [0123] 451 width [0124] 452 height