Waveguide polarizer, non-contact signal transmission system including waveguide polarizer, and antenna device

Abstract

There is provided a system for contactless signal transmission through a rotary joint, comprising a transmitter and a receiver wherein the transmitter is on a first part of the rotary joint and the receiver is on a second part of the rotary joint, the first part and the second part being opposite and separated by an air gap, the surface of the first part and the surface of the second part facing each other are perpendicular to the rotating shaft of the rotating joint; and a choke coil in the air gap contacting one of the first component and the second component, the choke coil including a printed circuit board having a through-hole coaxial with the rotation axis and an electromagnetic chip, each of the transmitter and the receiver including a hollow waveguide, at least the transmitter including a waveguide polarizer, the diameter of the waveguide polarizer is smaller than the diameter of the circular hollow waveguide, and two longitudinal radially opposed grooves are in the wall of the waveguide polarizer.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to a rotary joint comprising a waveguide polarizer, and to a contactless signal transmission system and an antenna device comprising the waveguide polarizer. BACKGROUND

[0002] The rapid development of robotics currently based on the growing demand for automation and robotic complexes in various areas of human activity, such as military, industrial, mining, etc., where there is a need to develop structures for transmitting signals to actuators of a robotic complex (robot) through the components (joints) of the robot. Such development is especially important for rotating components, such as rotating robot joints.

[0003] Currently, there are several ways to transmit signals through a rotary joint.

[0004] For example, a cable assembly can be used to transmit signals. In the assembly, a cable passes through a rotary joint. However, a cable assembly can have many drawbacks, including a limited rotation range of the joint, a relatively low reliability of the cable due to torque, a relatively high likelihood of cable damage during intense movements, etc.

[0005] Rotary contacts (slip rings) can be used, but they are not suitable for high data rates (HD video, etc.), have a relatively low reliability, can cause interference due to sparking between the contacts, and degrade over time due to mechanical wear. In addition, the mechanical components of rotary contacts can require high-precision manufacturing.

[0006] High-frequency rotary joints based on split coaxial or circular waveguides can also be used. However, high-frequency rotary joints can typically have a full-metal bulky design suitable only for stationary objects and require complex and high-precision assemblies. In addition, high-frequency rotary joints can provide only half-duplex channel connections for each line.

[0007] Data transmission using circularly polarized signals can enable full-duplex and multi-channel communication due to its symmetry, and thus can be used for rotary coupling. A polarizer can more easily provide a circularly polarized signal in a circular waveguide, which can allow efficient propagation of the circularly polarized signal due to its symmetry.

[0008] A microwave rotary coupler for rectangular waveguides connecting high frequency components can include an input component and an output component, where each component has a rectangular connector at one end and a circular waveguide at the other end. The two components are arranged so that the circular waveguides facing each other coaxially around their common axis (A) are rotatably mounted in a coupling transition. The microwave rotary coupler for rectangular waveguides can also include a polarizer disposed between the rectangular connector and the circular waveguide, through which at least one linearly polarized wave can be converted into a circularly polarized wave, or at least one circularly polarized wave can be converted into a linearly polarized wave. Furthermore, the rectangular connector is arranged axially with respect to the circular waveguide, and at least one rectangular waveguide can be connected parallel to the axis (A). However, the microwave rotary coupler for rectangular waveguides can have a bulky design.

[0009] A dual-band circular polarizer can be provided for simultaneously transforming two to four linearly polarized waves of two different frequency bands into two to four circularly polarized waves, and vice versa. The polarizer can include a waveguide of circular or square cross-sectional shape and two arrays of electrically conductive elements, where the waveguide is dimensioned to simultaneously propagate signals in two different frequency bands, and each array includes a pair of diametrically opposed rows of electrically conductive elements extending inward from the walls of the waveguide. However, the polarizer can be difficult to manufacture due to the electrically conductive elements that can be required to be used in the waveguide and the holding elements for the dielectric polarizers in the waveguide. The dielectric polarizers can introduce additional losses during signal transmission. Furthermore, the polarizer can only provide half-duplex communication.

[0010] A multi-channel microwave rotary coupler can include one single-channel rotary joint coaxially mounted on another, where each single-channel rotary joint is based on a coaxial line with a quarter- wavelength shorted ring in the form of a radial line and a matching transition at the end. The outer and center conductors of the coaxial line include a quarter- wavelength choke gap, the radial line has a variable height, and a cylindrical hollow metal rod passes through the center conductor of the single-channel coupler from the rotating part of the structure to the fixed part, which forms a choke gap with the fixed center conductor. The movable input of the single-channel rotary coupler is brought to the rotating part of the device structure through a coaxial feed line, which, in addition to the feed line of the upper single-channel coupler, passes through the inner cavity of the rod. This design is bulky and complex to assemble.

[0011] A dual-band dual-polarization splitter can be provided to form a novel coaxial waveguide orthogonal mode conversion and enable a structure of a coaxial circular waveguide fed simultaneously at higher and lower frequencies, reduce the length of high-frequency transmission lines, and reduce transmission losses.

[0012] Dual-polarization transmission in each frequency band can be implemented and can be flexibly switched between vertical and horizontal polarization when the dual-polarization has been converted to single-polarization. However, such a device can have a relatively bulky design and a complex assembly process.

[0013] Therefore, there is a need for a compact, reliable, simple and inexpensive system that provides high-speed and contactless signal transmission, including through the rotating joints of robots. SUMMARY

[0014] One or more embodiments provide a rotating joint comprising a waveguide polarizer and a contactless signal transmission system and antenna device comprising the waveguide polarizer.

[0015] According to an aspect of one or more embodiments, there is provided a system for contactless signal transmission through a rotating joint, the system comprising: a transmitter and a receiver, wherein the transmitter is on a first part of the rotating joint and the receiver is on a second part of the rotating joint, the first part of the rotating joint and the second part of the rotating joint are opposite to each other and separated by an air gap, a surface of the first part and a surface of the second part facing each other are perpendicular to an axis of rotation of the rotating joint; and a choke, in the air gap between the first part of the rotating joint and the second part of the rotating joint and in contact with one of the first part of the rotating joint and the second part of the rotating joint, the choke comprising a printed circuit board and an electromagnetic chip, wherein the printed circuit board has a circular through-hole coaxial with the axis of rotation of the rotating joint, the electromagnetic chip has an electromagnetic bandgap adjacent to the hole in the printed circuit board, the choke is configured to prevent signal leakage through the air gap, wherein each of the transmitter and the receiver comprises a circular hollow waveguide aligned with the axis of rotation, wherein at least the transmitter can comprise a waveguide polarizer, the waveguide polarizer is part of the circular hollow waveguide, a diameter of the waveguide polarizer is smaller than a diameter of the circular hollow waveguide, and wherein two longitudinally radially opposite grooves are formed in a wall of the waveguide polarizer.

[0016] The length of the waveguide polarizer can be a multiple of , wherein is a center wavelength of a signal operating range in the circular hollow waveguide.

[0017] The bottom surface of the groove can coincide with the inner wall of the circular hollow waveguide.

[0018] The groove can extend along the entire length of the waveguide polarizer.

[0019] The diameter of the hole in the printed circuit board can be equal to the diameter of the circular hollow waveguide in the transmitter and the receiver.

[0020] The distance from the hole in the printed circuit board of the choke to the EBG structure can be a multiple of , wherein is a center wavelength of a signal operating range in a planar parallel waveguide formed based on the surface of the first part and the surface of the second part and the choke.

[0021] The EBG structure can be adjacent to the aperture in the printed circuit board of the choke.

[0022] The EBG structure can include at least two rows of mushroom-shaped EBG (M-EBG) elements, each M-EBG including a conductive pad on an outer layer of the printed circuit board and a cylindrical pedestal formed by a metalized via and connecting the conductive pad to a conductive ground layer included in the printed circuit board.

[0023] The gap between the choke and each of the first component of the rotary joint and the second component of the rotary joint can be less than or equal to wherein, is a center wavelength of a signal operating range in the planar parallel waveguide formed based on the surface of the first component and the surface of the second component and the choke.

[0024] The printed circuit board of the choke can include four metalized conductive layers alternating with dielectric layers, and the EBG structure can be on both sides of the printed circuit board.

[0025] The M-EBG elements on opposite sides of the printed circuit board can be interconnected by vias.

[0026] The choke can be directly on one of the surface of the first component and the surface of the second component.

[0027] The printed circuit board of the choke can include two metalized conductive layers with a dielectric layer between the two metalized conductive layers, and based on providing electrical contact between a ground layer of the choke and a surface of said one of the rotary joint components, the EBG structure can be located on a side of the printed circuit board that is separated from a surface of the other one of the first component and the second component by an air gap.

[0028] The receiver can include a waveguide polarizer in a circular waveguide.

[0029] The signal can be a data signal for data transmission through the rotary joint. BRIEF DESCRIPTION OF DRAWINGS

[0030] The embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 is a cross-sectional view of a rotary joint according to one or more embodiments; Figure 2 shows the principle of operation of a polarizer according to one or more embodiments; Figure 3 is a view of a portion of a choke according to one or more embodiments; and Figure 4 shows an example design of electromagnetic bandgap (EBG) structure elements according to one or more embodiments. DETAILED DESCRIPTION

[0031] The embodiments are not limited to those described herein but can vary, without departing from the spirit and scope of the application, based on the information set forth in the description and the knowledge of the skilled person in the art.

[0032] Unless specifically stated otherwise, a reference to an element in the singular does not preclude the presence of plural elements.

[0033] In the above description of examples, directional terms (such as "above", "upper", "below", "lower", "up", "down", etc.) are used for convenience to refer to the accompanying drawings.

[0034] According to an aspect of one or more embodiments, there is provided a system for non-contact signal transmission through a rotary joint Figure 1 The upper part of the joint shown in FIG. 1 is movable and the lower part of the joint is fixed. However, embodiments are not limited thereto and the joint parts can be reversed. For example, the upper part of the joint can be fixed and the lower part of the joint can be movable. With respect to signal transmission, depending on the direction of transmission, the part of the signal transmission system on the fixed part of the joint can be either a transmitter that can send signals to the other part of the transmission system or a receiver that can receive signals from the other part of the transmission system. Similarly, the part of the signal transmission system on the movable part of the joint can be either a transmitter or a receiver. Furthermore, when the part of the signal transmission system on the fixed part of the joint is a transmitter, the part of the signal transmission system on the movable part of the joint is a receiver and vice versa. During operation, the direction of signal transmission can be repeatedly reversed, for example, the individual structures of the signal transmission system can change operation.

[0035] In one or more embodiments, Figure 1 The upper part of the joint shown in FIG. 1 is movable and the lower part of the joint is fixed. However, embodiments are not limited thereto and the joint parts can be reversed. For example, the upper part of the joint can be fixed and the lower part of the joint can be movable. With respect to signal transmission, depending on the direction of transmission, the part of the signal transmission system on the fixed part of the joint can be either a transmitter that can send signals to the other part of the transmission system or a receiver that can receive signals from the other part of the transmission system. Similarly, the part of the signal transmission system on the movable part of the joint can be either a transmitter or a receiver. Furthermore, when the part of the signal transmission system on the fixed part of the joint is a transmitter, the part of the signal transmission system on the movable part of the joint is a receiver and vice versa. During operation, the direction of signal transmission can be repeatedly reversed, for example, the individual structures of the signal transmission system can change operation.

[0036] The system for non-contact signal transmission through a rotary joint according to one or more embodiments can include a transmitter disposed on one part of the rotary joint (e.g., the fixed part of the joint) and a receiver disposed in the other part of the rotary joint (e.g., the movable part of the joint), the rotary joint parts being opposite to each other and separated by an air gap. Figure 1One or more embodiments of a rotary joint are illustrated. Surfaces of a fixed component and a movable component, parallel to each other and perpendicular to the rotation axis of the rotary joint, face each other, and a conductive layer is disposed on the surfaces. Each of the transmitter and receiver may include a circular hollow waveguide aligned with the rotation axis of the rotary joint. The waveguide in each of the fixed and movable components extends to a surface facing the other rotary joint component. Thus, the waveguides in the transmitter and receiver are coaxially opposed to each other and separated by an air gap. The diameter of the circular waveguide may be relative to H. 11 The operation and propagation of the pattern are determined, and can be less than or equal to those for higher patterns (such as E). 01 The diameter of the operation (etc.).

[0037] The transmitter may include a slotted circular waveguide polarizer disposed within a circular waveguide, and may have the form of a portion of a circular waveguide. The transmitter may have an inner diameter smaller than the diameter of the waveguide and two longitudinal grooves in the walls of the polarizer. The grooves are arranged radially opposite each other along the entire length of the polarizer parallel to the longitudinal axis of the waveguide (see...). Figure 2 The polarizer is configured to convert at least one linearly polarized wave into a circularly polarized wave, or at least one circularly polarized wave into a linearly polarized wave.

[0038] The polarizer according to one or more embodiments can be operated as follows. First, the main H is excited in a circular waveguide. 11 Electromagnetic waves of the mode (see Figure 2 (Upper cross-section). Waves can be excited by the output of a generator with an appropriately shaped output waveguide, or by a waveguide transition to the cross-section of a coaxial cable. Alternatively, wave excitation can be provided via a transition with an RF chip. The polarizer groove is arranged in the cross-section to be aligned with the main H... 11 The incident electromagnetic wave of the mode is at a 45-degree angle (see Figure 2 (Intermediate cross-section). H 11 The pattern is incident on the slotted polarizer at a 45-degree angle to the groove. Figure 2 The dashed arrow on the middle cross section is H. 11 The electric vector of the mode. In the polarizer, H 11 The pattern is divided into two pattern components: Ex and Ey. Figure 2 (Solid arrow on the middle cross section). The Ex component propagates across the groove on the polarizer, while the other component, Ey, propagates along the groove on the polarizer. The propagation constant of the Ex component is lower than that of the Ey component. Therefore, the phase difference between the Ex component and the Ey component that have passed through the groove is 90 degrees. The addition of the Ex and Ey components at the polarizer output forms the circularly polarized H. 11 model( Figure 2 (The semi-circular line on the lower middle cross section).

[0039] Therefore, when passing through the polarizer, the main H 11 Linearly polarized electromagnetic waves of the mode (see Figure 2 The upper cross section) is transformed into the main H 11 Circularly polarized electromagnetic waves of the mode (see Figure 2 (Lower cross-section).

[0040] The length of the polarizer was initially chosen as Multiples of, where, This is the center wavelength of the signal operating range in the circular waveguide. The length of the polarizer is then empirically adjusted after numerical simulation of the device. The inner diameter of the polarizer depends on the size of the groove and its characteristics (transverse and longitudinal wave propagation constants). In one or more embodiments, the bottom of the groove coincides with the inner wall of the underlying hollow waveguide. Therefore, the difference between the height (depth) of the groove and the inner diameter of the polarizer is matched to the inner diameter of the hollow waveguide. The depth and width of the groove are set to minimize reflection and loss in each signal channel. H is incident at a 45-degree angle relative to the groove. 11 The mode is equally divided into two components, and the phase of one component may lag the phase of the other component by 90 degrees. The shape of the groove may differ from... Figure 2 The diagram shows a shape that provides a 90-degree phase difference and equal division of the incident wave components.

[0041] although Figure 2 A single master H is shown 11 Mode formation is possible, but orthogonal principal H modes can also be formed simultaneously in the waveguide. 11 Mode. When passing through the polarizer, the orthogonal principal H 11 The mode is similarly converted into a relatively circularly polarized electromagnetic wave. Therefore, a waveguide with a polarizer can transmit signals simultaneously on two independent transmission channels.

[0042] Similarly, the polarizer described above can reverse at least one circularly polarized wave into a linearly polarized wave.

[0043] To obtain a signal from a linearly polarized wave for further transmission through electronic circuits, a waveguide transition section can be used to minimize the loss in converting the waveguide wave to the waveform of the subsequent waveguide structure. Microstrip waveguides can be used, which can be directly connected to receiving or transmitting devices (chips).

[0044] One or more embodiments of the polarizer can be easier to manufacture, have a more compact design, and may not contain any dielectric components, which reduces signal transmission loss over a relatively wide frequency range.

[0045] In one or more embodiments, the rotary joint may include a polarizer in both the transmitter and the receiver, thereby allowing bidirectional signal transmission.

[0046] According to one or more other embodiments, a polarizer may be included in the transmitter of a non-contact signal transmission system to provide unidirectional circularly polarized signal transmission.

[0047] Metamaterial chokes can be placed in the air gap between the fixed and movable parts of a rotary joint to prevent signal (energy) leakage through the air gap (see...). Figure 1 and Figure 3 The choke may include a printed circuit board (PCB) having a circular through-hole coaxial with the rotation axis of the rotary joint. The diameter of the hole in the PCB may match the diameter of the circular waveguides in the transmitter and receiver of the rotary joint. Figure 1 In one or more embodiments depicted, the diameter of the hole in the PCB is equal to the diameter of the circular waveguide in the transmitter and receiver of the rotary joint. The PCB according to one or more embodiments may include four metallized conductive layers alternating with dielectric layers. An electromagnetic bandgap (EBG) structure in the form of an electromagnetic chip with an electromagnetic bandgap (e.g., a structure forming a region where electromagnetic waves cannot propagate within a specific frequency range) is disposed around and spaced apart from the hole in the PCB. The EBG structure of one or more embodiments is placed on both sides of a multilayer PCB and may include at least two rows of mushroom-shaped EBG (M-EBG) elements on each side. For example, in... Figure 1 and Figure 3 In this embodiment, the EBG structure may include three rows of M-EBG elements; however, the embodiments are not limited thereto. Each M-EBG element may include a conductive pad placed on an outer layer of the PCB and a cylindrical base formed by metallized vias that connects the conductive pads to an inner conductive ground layer of the PCB. Figure 1 In this embodiment, M-EBG elements on opposite sides of the PCB are interconnected via through-holes. The EBG structure blocks surface wave propagation in the air gap between the PCB and the fixed and movable parts of the rotary joint, thereby preventing signal (energy) leakage from the rotary joint to the outside.

[0048] In one or more other embodiments, where the M-EBG elements on opposite sides of the PCB are not interconnected, additional M-EBG elements may be provided in the resulting gap within the choke PCB.

[0049] In some embodiments, M-EBG elements on opposite sides of the PCB may be offset relative to each other.

[0050] The distance between adjacent M-EBG elements in a row can be set to limit the propagation of stray waves (bandgap). The dispersion map shows the frequencies at which the limitation can be achieved. Therefore, the distance between M-EBG elements is determined based on the dispersion map of individual element cells and the PCB manufacturer's process capabilities (limitation of the gap between conductors). The distance between M-EBG element rows and the number of rows are selected based on the obtained dispersion map and the absence of patterns in the device's operating range.

[0051] In one or more other embodiments, the choke may have more than four conductive layers, and the EBG structure may have more than two rows of M-EBG elements.

[0052] The distance from the edge of the via in the choke PCB to the EBG structure can be set to ensure more efficient wave reflection and reduce signal transmission loss through the air gap, and can be... Multiples of, where, The EBG structure is the center wavelength of the signal operating range of a signal transmission system in a planar parallel waveguide formed by the surfaces of the rotating joint components facing each other and the choke coil. In one or more embodiments, the EBG structure is positioned at the edge of a hole in the PCB. The distance can be set based on the leakage signal, which propagates from the circular waveguide into the air gap, reaches the EBG structure, is reflected from the EBG structure with a 180-degree phase change, and returns into the circular waveguide, where it is added in phase with the wave of the signal propagating in the circular waveguide. In this way, signal (energy) leakage to the outside is prevented and thus interference with adjacent equipment is avoided, and signal transmission loss through the rotary joint is reduced.

[0053] In one or more other embodiments, the EBG structure may be placed close to a hole in the PCB.

[0054] Figure 4 The structure of an EBG element according to one or more embodiments is shown. The aforementioned M-EBG element is mushroom-shaped and consists of a pad (“mushroom cap”) located on an outer layer of the PCB and a cylindrical base (“mushroom leg”) extending from the pad to an inner ground layer of the PCB. In the PCB, the base of the EBG element is formed by through-holes. For example, the pad can be circular, square, triangular, hexagonal, etc. The size and shape of the pad affect the bandgap boundary and can be set based on the requirements of a specific application. In one or more other embodiments, the EBG element may have more than one base.

[0055] In one or more embodiments, the choke ring is fastened to a retaining component of the rotary joint. Fastening options may include, but are not limited to, screws passing through the washer, specific retaining plates, U-bolts, adhesive, etc.

[0056] like Figure 1As depicted, the choke ring is positioned at a certain distance in the air gap between the fixed and movable parts of the rotary joint assembly. The gap between the choke ring and each of the fixed and movable parts of the rotary joint can be 0 to... Within this range, it can be defined by the spacer.

[0057] In one or more embodiments, the choke can be placed directly on a fixed or movable part of the rotary joint. In this example, the outer conductive layer of the choke and the conductive layer of the fixed (movable) part may or may not be in electrical contact. Furthermore, even when the outer layer of the choke is in contact or partially in contact with the surface of the fixed (movable) part, the EBG structure can be formed on the surface of the outer layer because electrical contact cannot be guaranteed. In one or more embodiments, as described above, the choke can have at least four conductive layers to form the EBG structure.

[0058] In one or more other embodiments, an electrical contact may be provided between the grounding layer of the choke and a surface of one of the fixed and movable components (e.g., by welding these surfaces over the periphery or the entire area), the choke may have at least two conductive layers, and the EBG structure in the choke may be formed only on the side separated from the surface of the other of the fixed and movable components by an air gap.

[0059] The choke ring according to one or more embodiments is robust to inaccuracies in the assembly of the rotary joint. For example, the choke ring can perform its function and provide the aforementioned advantages even when it is slightly off-center from the rotation axis of the rotary joint or when it is tilted relative to the surface of a fixed or movable part.

[0060] The aforementioned signal can be a data signal (information signal) used to transmit data through a rotary joint or a power signal used for non-contact power transmission through a rotary joint.

[0061] In one or more embodiments, data is transmitted via a connector using millimeter-wave radio waves. The millimeter wavelength range used provides data rates up to several Gbps while maintaining a relatively compact waveguide size. In one or more other embodiments, depending on the desired data rate, other suitable wavelength ranges may be used for signal transmission.

[0062] Based on a non-contact structure for transmitting signals between waveguides mounted on fixed and movable components, the connector can rotate 360 ​​degrees without affecting signal transmission characteristics. Furthermore, this structure eliminates the need for additional shielding, reducing its weight and material content.

[0063] In one or more embodiments, the waveguide of the movable part of the connector can be connected to the antenna element, thereby forming a rotating antenna system. This configuration can provide a relatively compact, lightweight, and reliable data and / or power transmission system for the rotating antenna system.

[0064] The mobility of the joint components relative to each other can be ensured by placing ball bearings between them. Furthermore, the ball bearings can be replaced by any other suitable bearing or by elements that ensure the relative arrangement of the joint components within a given range and their ability to rotate relative to each other.

[0065] The operation of a rotary joint configured to transmit a signal from a transmitter in a fixed part of the rotary joint to a receiver in a movable part will be further described according to one or more embodiments.

[0066] First, in order to convert the signal into a linearly polarized electromagnetic wave, the primary (basic) H wave is excited in the circular waveguide of the fixed part of the rotary joint. 11 Electromagnetic waves of a certain pattern. H 11 The pattern is incident on the slotted polarizer at a 45-degree angle to the groove. The polarizer polarizes the main linearly polarized H... 11 The electromagnetic wave is converted into a circularly polarized electromagnetic wave. The circularly polarized electromagnetic wave propagates in a circular waveguide, passes through an air gap, and enters the circular waveguide of the movable part of the rotary joint. A choke in the air gap prevents the signal from leaking out of the rotary joint. Passing through a polarizer in the movable part of the rotary joint, the circularly polarized electromagnetic wave is converted into a linearly polarized electromagnetic wave.

[0067] Although the above example describes the operation of a rotary joint transmitting signals from a fixed part of the rotary joint to a movable part, signal transmission in the opposite direction can be performed in a similar manner.

[0068] Furthermore, since the signal is transmitted in the form of circularly polarized electromagnetic waves, the rotary joint can transmit signals with the same efficiency at any rotation angle of the movable part relative to the fixed part. Additionally, the rotary joint according to one or more embodiments can achieve full-duplex communication.

[0069] Mathematical simulations have shown that the rotary joint according to one or more embodiments provides a signal transmission reflection factor greater than or equal to 20 dB and a transmission loss less than or equal to 0.5 dB in the operating frequency band. Furthermore, it ensures channel isolation greater than 15 dB.

[0070] Therefore, one or more embodiments provide a relatively high-speed, non-contact system for transmitting signals via a rotary joint, which has a relatively compact, reliable, simple and inexpensive design.

[0071] A polarizer according to one or more embodiments may be used in a rotary joint for signal transmission.

[0072] According to another aspect of one or more embodiments, a polarizer can be used to form a circularly polarized antenna device. The antenna device may include a waveguide and a transmitting device having a polarizer according to one or more embodiments, such as a horn antenna. However, the embodiments are not limited thereto. In addition to horn antennas, other conventional types of antennas designed to transmit circularly polarized waves may also be used in the antenna device. Circularly polarized antenna devices can be used in both data transmission systems and wireless power transmission systems (such as wireless charging systems).

[0073] Antenna devices can have a relatively compact, easy-to-manufacture, low-loss, and low-cost design.

[0074] Although embodiments have been described with reference to the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope defined by the following claims and their equivalents.

Claims

1. A system for non-contact signal transmission via a rotary joint, comprising: A transmitter and a receiver, wherein the transmitter is on a first component of the rotary joint, and the receiver is on a second component of the rotary joint, the first component and the second component of the rotary joint facing each other and separated by an air gap, the surfaces of the first component and the second component facing each other being perpendicular to the rotation axis of the rotary joint; and A choke is disposed in the air gap between the first component and the second component of the rotary joint and contacts one of the first and second components of the rotary joint. The choke includes a printed circuit board and an electromagnetic chip. The printed circuit board has a circular through-hole coaxial with the rotation axis of the rotary joint, and the electromagnetic chip has an electromagnetic bandgap adjacent to the through-hole in the printed circuit board. The choke is configured to prevent signal leakage through the air gap. Each of the transmitter and the receiver includes a circular hollow waveguide aligned with the rotation axis. Wherein, at least the transmitter includes a waveguide polarizer, which is part of the circular hollow waveguide, and the diameter of the waveguide polarizer is smaller than the diameter of the circular hollow waveguide. Two longitudinally opposed radial grooves are formed in the wall of the waveguide polarizer.

2. The system for contactless signal transmission as described in claim 1, wherein, The length of the waveguide polarizer is Multiples of, where, It is the center wavelength of the signal operating range in the circular hollow waveguide.

3. The system for contactless signal transmission as described in claim 1, wherein, The bottom surface of the groove coincides with the inner wall of the circular hollow waveguide.

4. The system for contactless signal transmission as described in claim 1, wherein, The groove extends along the entire length of the waveguide polarizer.

5. The system for contactless signal transmission as described in claim 1, wherein, The diameter of the hole in the printed circuit board is equal to the diameter of the circular hollow waveguide in the transmitter and the receiver.

6. The system for contactless signal transmission as described in claim 1, wherein, The distance from the hole in the printed circuit board of the choke to the EBG structure is Multiples of, where, It is the center wavelength of the signal operating range in the planar parallel waveguide formed by the surfaces of the first component and the second component and the choke.

7. The system for contactless signal transmission as described in claim 1, wherein, The EBG structure is adjacent to the hole in the printed circuit board of the choke.

8. The system for contactless signal transmission as described in claim 1, wherein, The EBG structure includes at least two rows of mushroom-shaped EBG (M-EBG) elements, each M-EBG including a conductive pad on the outer layer of the printed circuit board and a cylindrical base formed by metallized vias and connecting the conductive pad to a conductive ground layer included in the printed circuit board.

9. The system for contactless signal transmission as described in claim 8, wherein, The gap between the choke ring and each of the first component and the second component of the rotary joint is less than or equal to 1. ,in, It is the center wavelength of the signal operating range in the planar parallel waveguide formed by the surfaces of the first component and the second component, and the choke coil.

10. The system for contactless signal transmission as described in claim 9, wherein, The printed circuit board of the choke includes four metallized conductive layers alternately disposed with dielectric layers, and The EBG structure is located on both sides of the printed circuit board.

11. The system for contactless signal transmission as claimed in claim 10, wherein, The M-EBG elements on opposite sides of the printed circuit board are interconnected via through-holes.

12. The system for contactless signal transmission as described in claim 8, wherein, The choke is located directly on one of the surfaces of the first component and the second component.

13. The system for contactless signal transmission as described in claim 12, wherein, The printed circuit board of the choke includes two metallized conductive layers, with a dielectric layer between the two metallized conductive layers. Wherein, based on providing electrical contact between the grounding layer of the choke and the surface of one of the rotary joint components, the EBG structure is located on the side of the printed circuit board separated from the surface of the first component and the surface of the second component by the air gap.

14. The system for contactless signal transmission as claimed in claim 1, wherein, The receiver includes a waveguide polarizer in the circular waveguide.

15. The system for contactless signal transmission as claimed in claim 1, wherein, The signal is a data signal used for data transmission through the rotary joint.

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