RU2744994C1 - Wireless board-to-board connection for high speed data transfer - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to high-speed wireless data transmission between different printed circuit boards or between sections of one printed circuit board. The technical result is to simplify manufacturing, reduce dimensions, reduce losses at high frequencies and improve performance. A device for transmitting signals is proposed, comprising: a waveguide comprising a first conducting base and a second conducting base, located parallel to each other, and side walls located between the first conducting base and the second conducting base, containing at least one structure like an electromagnetic crystal with a forbidden zone (EBG structure); and at least two directional antennas located opposite each other along the radiation axis, each antenna is made on the basis of a printed circuit board and contains: an EBG structure located on the upper and lower layers of the printed circuit board and made to prevent back radiation, and at least one matching element; a part of each of the antennas is located inside the waveguide, so that it completely covers the area between the antennas, forming a wireless channel in this area for transmitting electromagnetic signals, and the matching element is located near the wireless channel to match the antenna with the wireless channel.

EFFECT: improved performance.

16 cl, 38 dwg

Description

The technical field to which the invention relates

The present invention relates to radio engineering, and more specifically to high-speed wireless data transmission between different printed circuit boards or between portions of the same printed circuit board.

State of the art

The ever-increasing needs of users determine the rapid development of technologies in the field of communications and related fields. Currently, active development of systems using communication in the millimeter wave range is underway, such as data transmission systems 5G (28 GHz), WiGig (60 GHz), Beyond 5G (60 GHz), 6G (sub-THz). All of these and similar systems require highly efficient, functional yet simple and reliable components suitable for mass production.

One such component is a connection (or connector) for transferring data over a short distance between different printed circuit boards (PCBs) or between sections of the same printed circuit board. The main requirements for such connections are as follows: the connection should preferably be wireless, should have a low loss and compact signal delivery system, uncomplicated, cheap, compact, repeatable hardware design, applicable for mass production; it is preferable that the connection is not a separate component, but is part of a printed circuit board or built-in antenna; at the same time, stable reception should be supported at a high data transfer rate (> 2 Gbit / s); support for high performance multilayer PCB antennas is also preferred. However, prior art solutions, when trying to adapt them to the millimeter wavelength range, turn out to be unsuitable in order to maximize the above requirements, since they are either too expensive or too cumbersome, or require isolation, or require precise mechanical assembly, or do not provide the specified speed. data transmission.

In particular, the known electrical methods of board-to-board communication for data transmission over a short distance can be conditionally divided into two groups: wired connection (traditional galvanic connection using metal conductors) and wireless connection, which, in turn, can be divided into two subgroups: based on radio communication and connection based on optical communication.

As an example of a galvanic connection, SMD (surface mount) connectors are known, the components of which are mounted or positioned directly on the surface of a printed circuit board. As another example, RF (radio frequency) connectors are known, which are mounted on the surface of a printed circuit board and provide a connection between the printed circuit boards. Such methods of connecting printed circuit boards require a galvanic contact to provide a transition in the RF channel. These approaches have problems associated with, for example, low transmission frequencies: SMD connectors operate at frequencies up to 20 GHz, and RF connectors at up to 65 GHz. They are very sensitive to mechanical and thermal loads, as well as to assembly and soldering irregularities, which leads to low contact reliability, to a change in the parameters of the HF transition, to an increase in losses and, ultimately, to early contact failure. Therefore, a lot of assembly and installation time is required and a minimum distance between boards> 8 mm must be maintained.

As an example of wireless communication based on radio communication, data transmission using NFC (Near Field Communication) is known. Existing NFC technologies have magnetic field shielding issues requiring the use of a ferrite shield, which increases the footprint. Such solutions have a narrow bandwidth and low data transfer rate (up to 2.1 Mbit / s), since the carrier frequency of this technology is 13.56 MHz.

With regard to wireless communication based on optical communication, existing optical technologies have inherent problems with the need for a line of sight between the transmitter and the receiver, as well as with beam steering, which is required because the size of the receiver is small compared to the size of the device. This requires the use of sophisticated precision mechanics and tuning, which increases the footprint, dramatically alters the optical communication parameters and increases losses.

Speaking about specific technical solutions in the field of data transmission at high frequencies, to one degree or another close to the present invention, one can note, for example, document US 2019/0379426 A1 (12.12.2019), which discloses a transmitter and a receiver located on separate substrates or carriers, which are positioned relative to each other in such a way that the antennas of the transmitter / receiver pair during operation are spaced such a distance that near-field communication is achieved at the wavelengths of the transmitter carrier frequency. This document does not address the issue of joint integration between RFIC (Radio Frequency Integrated Circuit) and the antenna, as the antenna elements integrated in the RFIC are located on separate boards.

US 2017/0250726 A1 (08/31/2017) discloses a wireless connector that includes a first communication device and a second communication device. The first communication device is configured to transmit wirelessly by emitting a modulated signal comprising a carrier signal modulated with a digital signal. The second communication device is configured to receive this modulated signal. The first and second communication devices are connected through at least one wire connection that carries a signal used to demodulate the modulated signal. This solution requires at least one galvanic connection for demodulation.

US 8,041,227 B1 (18.10.2011) discloses a communication device capable of optical communication and near-field communication. The device includes an optical transceiver circuit fabricated on an integrated circuit chip and configured to transmit and receive far-field signals. The near-field transceiver circuitry is also fabricated on an integrated circuit chip and configured to transmit and receive near-field electromagnetic signals. Also provided is a control circuit for selectively enabling an optical transceiver circuit and a near field transceiver circuit responsive to an external control signal. The infrared data transmission proposed in this solution does not have a high speed, and in addition, an additional channel for interfacing is required.

US 2009/0289869 A1 (11/26/2009) discloses an antenna structure for transmitting electromagnetic energy between a crystal and an element outside the crystal, including a first resonant structure located on or inside the crystal and having a first resonant frequency. The antenna structure also includes a second resonant structure located in or on an element outside the crystal and having a second resonant frequency substantially the same as the first resonant frequency. The first resonant structure and the second resonant structure are mutually spaced at a near-field distance from each other to form an associated antenna structure that is configured to transfer electromagnetic energy between the crystal and the element outside the crystal. Electromagnetic energy has a selected wavelength in the wavelength range from microwaves to submillimeter waves. This solution is narrowband and does not support millimeter waves and sub-THz (sub-terahertz) range.

Another known technical solution in this area is the publication of N. Bayat-Makou, A. Kishk. Contactless Air-Filled Substrate Integrated Waveguide, IEEE Transactions on Microwave Theory and Techniques (Volume: 66, Issue: 6, June 2018). This document introduces for the first time a non-contact alternative to the substrate integrated waveguide (SIW) with air filled SIW (AF-SIW) implemented in a printed circuit board. The typical AF-SIW configuration requires precise and flawless bonding of the cover layers to the intermediate substrate. This requires a complex and expensive manufacturing process to operate efficiently at high frequencies. In this configuration (FIGS. 1A-1B), the waveguide is the upper and lower conductive layers, between which the air-filled medium is contained, and the printed circuit boards are located on the sides. The top and bottom layers of these embedded PCBs are modified to accommodate artificial magnetic conductor (AMC) conditions. The AMC surfaces on both sides of the waveguide substrate are made in the form of a periodic structure with a special type of unit cells. The AMC plates thus formed, which lie parallel to the conductive layers in the substrate region, prevent leakage outside the waveguide. However, this structure shows relatively high losses at the required frequencies and needs to be improved.

Thus, in the prior art, a need has arisen for creating a data connection, which would eliminate the following disadvantages of existing solutions:

- high losses;

- low data transfer rate;

- big sizes;

- high complexity of manufacturing;

- strong dependence on the quality of the contact between conductive elements.

The essence of the invention

In order to overcome at least some of the aforementioned disadvantages of the prior art, the present invention is directed to a printed circuit board-based data transmission device for millimeter-wave operation.

According to a first aspect of the present invention, there is provided an apparatus for transmitting signals, comprising:

- a waveguide containing:

a first conductive base and a second conductive base parallel to each other, and

located between the first conductive base and the second conductive base side walls containing at least one EBG-structure (electromagnetic band gap, structure like an electromagnetic crystal with a band gap); and

- at least two directional antennas located opposite each other along the radiation axis, each antenna being made on the basis of a printed circuit board and containing:

An EBG structure located on the top and bottom layers of the printed circuit board and configured to prevent back radiation, and

at least one matching element;

wherein at least part of each of the antennas is located inside the waveguide, so that it completely covers the area between the antennas, forming in this area a wireless channel for transmitting electromagnetic signals,

wherein said at least one matching element is located near the wireless channel and is configured to match the antenna with the wireless channel.

In one embodiment, the EBG structure contains a plurality of cells adjacent to each other in a two-dimensional periodic lattice, each cell containing:

parallel conductive portions within the first and second conductive layers of the printed circuit board, and

a conductive element passing through the thickness of the dielectric layer of the printed circuit board and connecting said conductive portions to each other;

wherein at least within one of the first and second conductive layers of the printed circuit board, said conductive portions of adjacent cells are not electrically connected to each other.

In one embodiment, the EBG structure is separated from at least one of the bases by a dielectric gap,

the device additionally contains:

spacers located between the EBG structure and the base in the region of the said gap, which fix the EBG structure and provide the said gap, while the spacers are located so as not to close adjacent cells of the EBG structure with each other.

In one embodiment, the spacers are conductive, with the spacer distance from the boundary between the EBG structure and said wireless channel being more than three cells of the EBG structure.

In one embodiment, the conductive element of the EBG-structure cell is made in the form of a through metallized hole (VIA, Vertical Interconnect Access), and the conductive section of the EBG-structure cell is made in the form of a contact pad.

In one embodiment, at least one of the antennas comprises, within the multilayer printed circuit board, at least two EBG structures and an SIW waveguide (implemented in a printed circuit board, a pin wall waveguide), enclosed between said at least two EBG structures,

moreover, the conductive sections of adjacent cells of EBG structures within those conductive layers of the printed circuit board that form the upper and lower base of the SIW waveguide are electrically connected to each other,

the conductive sections of adjacent cells of EBG structures within the outermost conductive layers of the printed circuit board are not electrically connected to each other.

In one embodiment, at least a portion of the EBG structures of the sidewalls of the waveguide and said at least one of the antennas constitute a single EBG structure within a single printed circuit board.

In one embodiment, at least a portion of the waveguide and at least one of the antennas are integrated into a single printed circuit board.

In one embodiment, the antennas are configured to transmit and receive over a wireless channel two wave types perpendicular to each other.

In one embodiment, at least one of the antennas comprises a coiled patch antenna integrated into the printed circuit board and fed by a microstrip waveguide.

In one embodiment, at least one of the antennas comprises a dipole antenna integrated into the printed circuit board.

In one embodiment, the antennas are positioned in the waveguide such that the radiation axis is parallel to the bases.

In one embodiment, the antennas are positioned in the waveguide such that the radiation axis is perpendicular to the bases.

In one embodiment, the first waveguide base, side walls and at least one of the antennas are integrated into the first printed circuit board, and the second base and at least one other of the antennas are integrated into the second printed circuit board.

In one embodiment, the side walls comprise at least two EBG structures and further comprise a conductive plate comprising a cutout in the wireless channel region, the first waveguide base, at least one of the EBG structures of the side walls, and at least one of the antennas integrated into the first printed circuit board, and the second base, at least one other of the EBG side wall structures and at least one other of the antennas are integrated into the second printed circuit board.

In one embodiment, the side walls comprise a plurality of EBG structures arranged one above the other, separated from each other by conductive plates not in contact with the EBG structures.

Technical result

The present invention provides a device that is capable of operating in the mm-band and sub-THz band, is simplified to manufacture, more compact and inexpensive, while exhibiting improved performance over prior art solutions.

Brief Description of Drawings

FIG. 1A-1B show a prior art AF-SIW non-contact waveguide.

FIG. 2 is a schematic cross-sectional perspective view of a signal transmission device according to the present invention.

FIG. 3 is a schematic cross-sectional side view of a signal transmission device according to the present invention.

FIG. 4 is a schematic cross-sectional top view of a signal transmission device according to the present invention.

FIG. 5 shows the directions of permissible deviations in the relative positioning of the device elements during assembly.

FIG. 6 is another schematic cross-sectional side view of a signal transmission device according to the present invention.

FIG. 7 shows the equivalent circuit of the proposed device for the case of a plane-parallel waveguide without side walls.

FIG. 8 shows the distribution of the power flow in the antenna.

FIG. 9A-9B show exemplary electromagnetic field distribution diagrams in a plane-parallel waveguide.

FIG. 10 shows the simulation results of the proposed device for the case of a plane-parallel waveguide without side walls.

FIG. 11 shows the structure of the unit cell of the EBG structure.

FIG. 12 shows an equivalent diagram of an EBG structure.

FIG. 13 shows the frequency response of a waveguide with an EBG structure.

FIG. 14 shows the principle of obtaining a new layout of the EBG structure.

FIG. 15 shows the structure of a truncated EBG unit cell.

FIG. 16 shows an equivalent diagram of a truncated EBG structure.

FIG. 17 shows the frequency response of a truncated EBG waveguide.

FIG. 18 shows a further embodiment of the EBG structure.

FIG. 19 is a schematic representation of an electric field in a wireless channel.

FIG. 20 shows a graph of the distribution of the electric field in the waveguide.

FIG. 21 shows an exemplary design for simulating air gap variations.

FIG. 22A-22C show simulation results for air gap variations.

FIG. 23A-23E show the principle of forming a SIW antenna between truncated EBG structures.

FIG. 24 is a schematic diagram of a test setup for simulating an antenna based on a SIW waveguide enclosed in truncated EBG structures.

FIG. 25 shows the simulation results for the case of FIG. 24.

FIG. 26 shows an example of a folded patch antenna.

FIG. 27 shows the radiation diagram for the case with a folded patch antenna.

FIG. 28 shows the simulation results for the case with a folded patch antenna.

FIG. 29 shows an example of a dipole antenna.

FIG. 30 shows the radiation pattern for the case with a dipole antenna.

FIG. 31 shows the simulation results for the case with a dipole antenna.

FIG. 32 shows an example of integrating antenna and sidewalls into a single printed circuit board.

FIG. 33, 34, 35, 36A and 36B show embodiments with signaling perpendicular to the plane of the bases.

FIG. 37 shows signaling in full duplex mode.

FIG. 38 shows a multilayer EBG structure.

It should be understood that the figures may be presented schematically and not to scale and are intended primarily to enhance the understanding of the present invention.

Detailed description

General description of the device

FIG. 2-4 show a schematic diagram of a signaling apparatus 100 according to the present invention. The device 100 includes a waveguide 110 (not shown separately in the drawings) and directional antennas (or adapters) 120 and 121 located therein.

The upper and lower bases of the waveguide 110 are formed by conductive (eg, metal) plates 111 and 112 arranged parallel to each other, that is, they form a plane-parallel waveguide. The side walls of the waveguide 110 are formed by EBG structures (electromagnetic band gap) 113 located between the bases, whereby the walls together with the bases form a rectangular waveguide in which electromagnetic waves can propagate. Each EBG structure is separated from one of the bases or from both bases by a dielectric (eg, air) gap and at the same time creates artificial magnetic conductor (AMC) conditions and blocks the leakage of waves from the waveguide into the external space.

Antennas 120 and 121 are located opposite each other along the radiation axis. In addition, the antennas 120 and 121 are based on a pin wall waveguide (SIW) implemented on a printed circuit board. As an example, in FIG. 2-4 show that the first antenna is part of the first printed circuit board 130, and the second antenna is part of the second printed circuit board 131. Further, other arrangements of printed circuit boards, antennas and EBG structures will be shown in this document, so it should be understood that the present invention is not limited to these options.

Thus, between the antennas inside the waveguide, an area filled with air or other dielectric remains, in which a wireless channel 140 is formed for transmitting electromagnetic signals 150 between the antennas. To ensure the conditions for free propagation of the signal 150 in the wireless channel 140, the distance between the bases is not less than λ / 2 (half the wavelength) for the transmitted signal. On the other hand, to prevent spurious radiation and leaks outside the wireless channel 140, the distance between the inner boundaries of the side walls should be no more than λ, the distance between the edges of the antennas should be no less than λ / 4 (quarter wavelength) and no more than λ, and the distance there should be no more than λ between the bases, that is, the maximum size of the wireless channel 140 is a λхλхλ cube. In addition, the size of the gap between the EBG structure and the base should not exceed λ / 4.

A high frequency signal 150 from RFIC (Radio Frequency Integrated Circuit) located on the side of the first printed circuit board 130 enters the input 160 of the device 100 (which is the input of the first antenna 120), is emitted by it into the wireless channel 140, is received from the wireless channel by the antenna 121 and from the output 170 (which is the output of the second antenna 121) is transmitted to the RFIC located on the side of the second printed circuit board 131. It should be understood that the indications of "in" and "out" are arbitrary and the signal can be transmitted in the opposite direction if necessary.

Each antenna (for example, in the SIW waveguide) may have one or more matching elements 180 and 181 (Fig. 6) located near the wireless channel 140. The matching element allows an electromagnetic wave to be radiated from the SIW waveguide to the wireless channel 140 with minimal backward losses.

Considering the operation of the device 100, the following can be noted. If we imagine that the first antenna is an isotropic radiator, then it radiates electromagnetic energy of the same intensity in all directions without loss. The radiation pattern of such an antenna is circular in all sections. If we assume that the aperture of the second receiving antenna has a size a x b and is located at a distance R from the first antenna, then in the most general case, in the absence of obstacles around an isotropic emitter, radiation occurs entirely in three-dimensional space, and the received power at the second antenna will be

.

...

If a plane-parallel waveguide of two parallel bases is placed around the first antenna at a distance a from each other, then the radiation will occur only in the plane, but in all directions, and then the received power on the second antenna will increase (2R) / b times.

By placing side walls in the form of EBG structures around the first antenna, it is possible to provide radiation only in a straight line, but in two directions, that is, the received power at the second antenna will increase by a factor of πR / a.

Finally, since the first antenna in the present invention is in fact directional, only a straight line radiation in one direction is provided, and therefore the received power at the second antenna will be

,

,

that is, all the power of the source in the absence of losses in the arrangement according to the present invention must go to the receiver.

Accordingly, with the proposed device 100, the signal is transmitted with high efficiency and low loss, while it is suitable for transmitting data signals at high rates up to 2 Gbit / s or more.

It should be noted that parallel conductive plates are present by default in many electronic devices, and the technology for manufacturing printed circuit boards is widely used, developed and cheap. That is, it is possible to create the proposed waveguide structure simply by placing conductive bases nearby or in contact with printed circuit boards containing antennas and EBG structures. The proposed device 100 does not require a galvanic contact, not only between two printed circuit boards, between which it is necessary to transmit signals, but generally between different elements of the device. Moreover, as shown in FIG. 5, all elements of the device do not have strict assembly tolerances (~ 1 mm in the plane between the bases, ~ 500 μm perpendicular to the bases). In order not to clutter the drawing with unnecessary arrows, for convenience of understanding, in FIG. 5 shows only arrows indicating directions of tolerances, while reference designations of the corresponding elements can be found in FIG. 4, which shows the same top view as FIG. 5. Thus, the present invention provides for simplification of assembly and manufacture, since such a structure greatly simplifies the manufacturing process and reduces the requirements for accuracy and manufacturing tolerances.

Hereinafter, the elements of the signaling apparatus 100 will be described in more detail.

Plane-parallel waveguide

In the present invention, a plane-parallel waveguide is used to concentrate an electromagnetic field in a wireless channel between printed circuit boards. FIG. 6, the dotted line with an arrow shows that the electromagnetic wave can be excited by both the first antenna for transmission to the second, and the second antenna for transmission to the first.

For the electromagnetic wave to be transmitted without loss, the condition of resonance with the required center frequency must be met in the wireless channel. FIG. 7 shows an equivalent diagram of the proposed device 100 to aid in calculations. It shows that at the interface between the two media between the antenna and the wireless channel, inductive coupling occurs in the form of a transformer. Since the plane-parallel waveguide does not have side walls, there is an open space around the wireless channel, into which part of the antenna radiation can go. Therefore, each medium (first antenna, wireless channel, second antenna) has some intrinsic impedance R _{antenna # 1} , R _leakage , R _{antenna # 2} . To obtain the resonance condition, it is necessary to use a matching element with capacitive properties in each antenna. The matching elements in the first antenna and in the second antenna have capacitances C1 and C2, respectively, as illustrated in FIG. 7. Next, you need to make the appropriate calculations. The principles of such calculations are known to the person skilled in the art and will not be detailed herein.

FIG. 8 shows the distribution of the power flow in the antenna. Item reference numbers are again not shown for ease of understanding and may be found in other drawings, such as FIG. 3 and 6. Possible directions of wave propagation include transmission, reflection, and leakage into the waveguide. Exemplary diagrams of the distribution of the electromagnetic field in a plane-parallel waveguide are shown in FIG. 9A-9B, side and top views, respectively. A fairly large part of the radiation excited by the first antenna enters the second antenna through the region of the wireless channel, and a part spreads to the sides of it, that is, some leakage occurs.

The present inventors simulated the case of a plane-parallel waveguide without sidewalls at 60 GHz and obtained the corresponding loss plots shown in FIG. 10. In particular, the following S-parameters were obtained: the transmission loss factor in the operating frequency band was about -7 dB, the return loss factor was about -22 dB. As you can see, most of the signal (about 75%) is transmitted from one antenna to another antenna without high return loss and leakage, while the antenna matching is not degraded. The losses are about 25% of the radiated power. Accordingly, a plane-parallel waveguide really allows you to focus the electromagnetic field in the wireless channel between the antennas. Thus, the radiation is isolated in one plane and a relatively high energy efficiency is already achieved. It will now be shown how the loss reduction is achieved in the present invention.

Sidewalls of a waveguide with EBG structures

To prevent leakage into open space, side walls formed by EBG structures are used. Together with the bases, they form a rectangular waveguide.

The EBG structure is made on the basis of a double-sided printed circuit board and contains many cells located next to each other in the form of a two-dimensional periodic lattice. The unit cell structure of the EBG structure is shown in FIG. 11. The unit cell contains parallel conductive portions (eg, contact pads) of the upper and lower conductive layers of the printed circuit board, interconnected by a conductive element passing through the thickness of the dielectric layer of the printed circuit board - for example, a plated through hole (VIA). The size and shape of the conductive sections are selected to meet the requirements of the specific application. In the general case, the conductive sections of neighboring cells are not electrically connected to each other, and the EBG structure itself is separated from the bases by a dielectric (for example, air) gap.

An equivalent diagram of such an EBG structure is shown in FIG. 12. In particular, the air-filled regions between the bases and the conductive portions have capacitive properties, the regions between the conductive portions of adjacent cells are also capacitive, and the VIA regions have inductive properties. Thus, a high-Q resonator is formed.

Accordingly, the EBG structure blocks the propagation of waves (leakage) at the required frequencies from the wireless channel to the external space due to the formation, in the operating frequency range, of a bandgap in the region of the wireless channel between the bases and side walls. The present inventors simulated a PCB based EBG structure that required a Rogers RO4003® microwave backing and obtained the corresponding plots shown in FIG. 13. As shown in FIG. 13 is a graph of the dependence of the frequency of the signal transmitted through the EBG structure on the phase shift realized in each cell of this structure, in a certain frequency range (in the blocking zone, which is located between two parallel lines on the vertical axis), wave propagation is impossible in this structure. Thus, the first mode propagates at frequencies up to 54 GHz, the remaining modes - at frequencies from 71 GHz. Thus, due to the EBG structure, the power in the operating frequency range (for example, about 60 GHz) should not flow out of the waveguide, but should completely enter the receiving antenna through the wireless channel.

That is, with a compact size, the proposed device has very low losses, and at the same time, its assembly does not require strong and reliable contact between the layers.

Although this arrangement of the EBG structure is quite effective, each change in geometry leads to the need to recalculate the entire EBG structure to maintain the required bandwidth. This makes it possible to design only a single-mode waveguide due to the limitation on the height of the waveguide. When trying to transmit waves in a wide frequency range, some of the waves can leak into the gaps between the VIAs and into the gaps between the bases and the conductive sections of the EBG structure. In addition, this arrangement requires the use of high quality RF materials such as the one discussed above. Therefore, despite its high efficiency, this arrangement of the EBG structure has a relatively narrow field of application.

To increase the versatility, it is proposed to use the new EBG structure layout. Specifically, as shown in FIG. 14, it is proposed to split each cell into two in the VIA area and short the VIA to the ground plate. As a result, the structure of the unit cell of the truncated EBG structure takes the form shown in FIG. 15. In this case, the unit cell contains parallel to each other conductive sections (for example, contact pads) of the upper and lower conductive layers of the printed circuit board, connected to each other by a conductive element passing through the thickness of the dielectric layer of the printed circuit board - for example, through a plated hole (VIA) ... The conductive sections of neighboring cells in one layer are not electrically connected to each other, but in the other layer they are electrically connected to each other (in fact, they are all combined into the ground layer). On the side where the conductive portions of adjacent cells are not electrically connected to each other, the truncated EBG structure can be separated from the nearby base by a dielectric (eg, air) gap.

An equivalent diagram of such a truncated EBG structure is shown in FIG. 16. In particular, the air-filled regions between the base and the conductive portions have capacitive properties, the region between the conductive portions of adjacent cells is also capacitive, and the VIA regions have inductive properties. Thus, there is only one air gap, which requires less inductance, and therefore results in a lower Q factor than in the previous arrangement.

The present inventors have simulated a truncated EBG structure, and in this case, the PCB required a conventional FR4 substrate. The corresponding graphs are shown in FIG. 17. As shown in FIG. 17 is the graph of the dependence of the frequency of the signal transmitted through the truncated EBG structure on the phase shift, the first mode propagates at frequencies up to 47 GHz, the remaining modes - at frequencies from 75 GHz. Thus, the use of a truncated EBG structure allows the top and bottom pads to be decoupled from each other, reduces inductance and expands the operating bandwidth. As in the previous version, with a compact size, the proposed device has very low losses, and at the same time its assembly does not require strong and reliable contact between the layers. Moreover, this arrangement allows the use of commonly used PCB materials, further simplifying the fabrication of the device.

FIG. 18 shows a further embodiment of an EBG structure according to the present invention. The two truncated EBG structures are mirrored with respect to their ground plates, and the VIAs of the first truncated EBG structure are aligned and connected to the corresponding VIAs of the second truncated EBG structure. Thus, EBG structures can be located on both the outer and inner layers of the PCB. Between the ground plates (layers) of these two truncated EBG structures, an intermediate layer can be located, for example, in the form of a printed circuit board substrate, through the thickness of which the first VIAs and the second VIAs are interconnected. The connection can also be implemented as VIA. The distance between the ground plates of the two truncated EBG structures, as well as the distance between adjacent VIAs, must be less than half the wavelength in the substrate material to prevent RF power from leaking into this intermediate layer. The minimum number of rows of EBG cells sufficient to prevent leakage is 2. If required, multiple intermediate dielectric layers separated by ground layers can be used, provided the above dimensions are maintained between VIAs and between ground layers. All this makes it possible to vary the dimensions of the structure without serious restrictions (for example, to increase the thickness). This EBG structure allows both horizontal waveguide structure and vertical waveguide structure to be designed.

The present inventors have simulated this EBG structure, resulting in a graph of the electric field distribution in the waveguide around the EBG structure. A schematic representation of an electric field in a wireless channel is shown in FIG. 19 and a simulated graph is shown in FIG. 20. Thin short arrows show the minima of the electric field values, and bold long arrows indicate the maxima of the electric field values. As you can see, there is practically no leakage, and the entire field is concentrated in the area of the wireless channel.

Spacers can be located between the EBG structure and the base in the air gap area, which fix the EBG structure and ensure this gap. The dividers can be separate elements, or part of an EBG board, or part of the bases. For example, in one embodiment, the spacers can be formed as protrusions on the waveguide base and on the layers of the printed circuit boards, and in another embodiment, the spacers can be separate elements that are inserted between the layers during manufacture. This provides additional design versatility and ease of manufacture. Spacers can be either conductive or non-conductive, but must not short-circuit adjacent EBG elements. If conductive spacers are to be used, the distance from them to the boundary between the EBG structure and the wireless channel must be more than three cells of the EBG structure to prevent unwanted phenomena in the waveguide.

In additional embodiments, all or some of the spacers may not only function as an air gap between the EBG structure and the base, but also function as a fastener. For example, glue drops can be used as spacers or part of them, or fasteners such as screws to tie the structure can pass through the spacers. In other embodiments, the fastening of the structural elements of the waveguide and antenna can be performed by other means, including not within the spacers. Each of these possibilities also allows for increased design versatility.

Although it is suggested in this document to separate the EBG structures from the bases with spacers to form an air gap in order to provide the best performance above, in fact, variations in the size of the air gap between them are quite acceptable. As an example, the present inventors have simulated gap variations for the 60 GHz case (FIG. 21). In this case, the wavelength λ is 5 mm. The distance between the bases was chosen equal to 2.27 mm, the thickness of the EBG structure was chosen equal to 1.5 mm, the distance between the EBG structures was chosen equal to 4 mm. The vertical position of the EBG structure in the waveguide varied in the range 0 mm ... 0.77 mm, i.e. from galvanic contact with the lower base of the waveguide to galvanic contact with the upper base of the waveguide (it should be recalled that the maximum allowable gap is a quarter of the wavelength of the transmitted signal, that is, in this case, 1.25 mm, therefore 0.77 mm is acceptable). As shown in the graphs in FIG. 22A-22C, the parameters of the air gap hz do not have a significant effect on the parameters of the device as a whole: the spread of parameters (reflection coefficient, transmission coefficient and group delay) is small in the entire investigated range of air gap sizes. Thus, it can be noted once again that the proposed design of the device as a whole is extremely versatile and does not require high manufacturing accuracy.

Accordingly, a broadband EBG structure with an independent change in thickness is obtained, which can be multilayer if necessary to increase the thickness and to overcome technological limitations. That is, it provides isolation of radiation in an unnecessary direction, variable thickness of the assembly, widening the bandwidth, reducing the sensitivity to assembly accuracy, expanding the possible field of application, and the possibility of using conventional materials for manufacturing printed circuit boards.

Antenna

The following describes in more detail exemplary embodiments of antennas in the proposed device.

The antenna is implemented on the basis of a printed circuit board and contains at least one matching element and a resonant structure. Resonant structure located on the top and bottom layers to prevent back radiation. Matching elements are designed to reduce losses, for example, by matching the antenna to the wireless channel, as shown above. The antenna is at least partially housed within the resonant waveguide structure. Antenna power supply can be different: using a microstrip line, a strip line, SIW-waveguide and others. In the case of a SIW waveguide, power is supplied between the resonant structure in the middle layers of the PCB.

Turning in particular to the case of using a SIW waveguide, it can be enclosed between two truncated EBG structures. For this, not all VIAs of truncated EBG structures should be connected to each other, but only the extreme ones, in order to form a SIW waveguide in the cavity between them, as shown generally in FIG. 3 and as shown in more detail in FIG. 23A-23E. This antenna is part of the printed circuit board, and the EBG structure serves here as a back-light insulator. Provides highly efficient radiation in a given direction in the wireless channel, and no external parts, except for the actual printed circuit board, which contains all the elements at once, are not required.

The authors of the present invention have simulated this arrangement of the proposed device, in which EBG structures are placed between the bases, and an antenna is placed between the bases and EBG structures, which, in turn, contains a SIW waveguide enclosed between truncated EBG structures. A schematic representation of the test setup is shown in FIG. 24 with arrow explanations of how the transmitted wave propagates, the reflected wave propagates, and how leakage can occur. A simulated graph is shown in FIG. 25. In particular, the following S-parameters were obtained: the transmission loss ratio in the operating frequency band was about -1 dB, the return loss ratio was about -21 dB, the isolation was about -37 dB. As you can see, the signal is transmitted from the antenna to the wireless channel with minimal loss, that is, without high reflection and leakage losses, while the antenna matching is not degraded, that is, the EBG structures built into the antenna made it possible to further reduce the leakage. The losses have been reduced to about 20% of the radiated power. Accordingly, the proposed device makes it possible to concentrate the electromagnetic field in the wireless channel between the antennas, the radiation is isolated strictly in a given direction, and an increase in energy efficiency is achieved.

As indicated above, other antenna implementations are possible. For example, the antenna may comprise a coiled patch antenna integrated into a printed circuit board and powered by a microstrip waveguide (FIG. 26). The radiation pattern of such an antenna is shown in FIG. 27, and the S-parameter graph is in FIG. 28.

In another embodiment, the antenna may comprise a dipole antenna integrated into the printed circuit board, namely located at the edge of the printed circuit board (FIG. 29). The radiation pattern of such an antenna is shown in FIG. 30, and the S-parameter plot is in FIG. 31.

An embodiment is also possible in which the first antenna 120 and at least part (eg, half) of the EBG structures 113 of the sidewalls of the waveguide constitute a single EBG structure within a single printed circuit board. Likewise, a second antenna 121 and at least a portion (eg, the other half) of the EBG structures 113 of the waveguide sidewalls can be incorporated into a single printed circuit board. In yet another embodiment, the antenna, together with both side walls, is entirely integrated into one printed circuit board, and the other antenna is mated to this structure to form a wireless channel. In such cases, the manufacture of the proposed device is further simplified.

Above in this document, only examples have been described in which the antennas are located in the waveguide in such a way that the radiation axis is parallel to the bases. However, embodiments are also possible in which the antennas are located in the waveguide in such a way that the radiation axis is perpendicular to the bases.

In particular, antennas 120 and 121 can be stacked on top of each other — for example, in different modules, as shown in FIG. 33-36.

In this case, the resonant structures (EBG structures 113), limiting the radiation, can be separate elements and are located at the edges of the antennas between two modules with an air gap between the EBG structures and the bases (Fig. 33).

In another embodiment, EBG structures 113 are integrated into the same boards 130 and 131 in which antennas 120 and 121 are implemented, and span these antennas, and the distance between the EBG structures is such as to ensure transmission and prevent leakage (Fig. 34) ...

In another embodiment, EBG structures 113 are integrated into the same boards 130 and 131 in which antennas 120 and 121 are implemented and encompass these antennas. The second module is covered with a ground plane 190, which serves as one of the bases for the EBG structure of the first module, and the distance between the EBG structure of the first module and the outer ground plane of the second module is such as to ensure transmission and prevent leakage (Fig. 35).

In another embodiment, EBG structures 113 are integrated into the same boards 130 and 131 in which antennas 120 and 121 are implemented and encompass these antennas. Between the EBG structures, there is additionally an intermediate conductive plate 191 containing a cutout in the area of the wireless channel (FIGS. 36A, 36B).

Above in this document, the default examples were described in which one type of wave is transmitted over the wireless channel. However, the proposed device is so versatile that it allows two types of waves to be transmitted and received via a wireless channel, perpendicular to each other (Fig. 37). The distance between the bases of the waveguide must be sufficient for the propagation of additional modes. At the same time, high isolation between modes is provided, which allows you to transmit and receive data simultaneously, that is, in full duplex mode.

As indicated above, the size, shape and location of the conductive sections of the EBG cells are selected according to the requirements of a particular application. The conductive sections of the cells of the EBG structure can be made in the form of an octagon, square, circle, triangle, etc. The conductive sections do not need to be centered with respect to the VIA and can be offset. The principles of sizing the structure of an electromagnetic crystal with a band gap are known to those skilled in the art and are not the subject of this invention. The main requirement is only that the structure must be periodic. In this case, the lattice can be square, rectangular, triangular, etc. Thus, the flexibility of the placement of the cells and the simple adaptation of the waveguide to the internal structures of the device in which it is to be used, as well as the convenient adjustment of the required electrical characteristics are provided.

If desired, any of the EBG structures disclosed in the present invention can be layered on top of each other. In this case, they can be separated by an intermediate earth layer (Fig. 38).

Useful effect

Thus, the signal transmission apparatus according to the present invention provides many advantages over the prior art. In particular, it provides a wireless channel with improved energy efficiency, reduced RF power leakage, and simplified assembly and fabrication. The data transfer rate has been increased to 2 Gbps or more (experimental tests show that it is possible to transfer data at 2.3 Gbps without significant jitter). The geometry of the device is more resistant to mechanical distortion. No external shielding required. The minimum distance between the boards is reduced to less than 1 mm. Provides increased contact reliability and reduced requirements for technological tolerances due to the use of non-contact mechanics. This does not require beam steering. In addition, the present invention provides a simplified integration with PCB technologies, an increase in the operating frequency band, an increase in compactness and the ability to vary the size of the device, the absence of the need for a galvanic connection between the elements of the device. The proposed device is scalable, compact and broadband and has low losses and can be successfully used for applications in the millimeter and sub-THz ranges.

It should be understood that this document shows the principle of construction and basic examples of an apparatus for transmitting RF signals. A person skilled in the art using these principles will be able to obtain other embodiments of the invention without any creative effort.

Application

The signal transmission device according to the present invention can be used in electronic devices that require transmission of RF signals over a short distance, for example, in the millimeter-wave range for mobile networks 5G (28 GHz), WiGig (60 GHz), Beyond 5G (60 GHz) ), 6G (sub-THz), for automotive radar systems (24 GHz, 79 GHz), for short-range communication (60 GHz), for smart home systems and other mm-range adaptive intelligent systems, for automotive navigation , for the Internet of Things (IoT), wireless charging, etc.

It should be understood that while terms such as "first", "second", "third" and the like may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components , areas, layers and / or sections should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer, or section may be called a second element, component, region, layer, or section without departing from the scope of the present invention. As used herein, the term "and / or" includes any and all combinations of one or more of the respective listed positions. Elements mentioned in the singular do not exclude the plurality of elements, unless otherwise specified.

The functionality of an item referred to in the specification or claims as a single item may be practiced by several device components, and vice versa, the functionality of items specified in the specification or claims as several separate items can be implemented in practice by a single component.

In one embodiment, the elements / blocks of the proposed device are located in a common housing, can be placed on the same frame / structure / printed circuit board and are connected to each other structurally by means of assembly (assembly) operations and functionally by means of communication lines. The mentioned lines or channels of communication, unless otherwise indicated, are standard communication lines known to those skilled in the art, the material implementation of which does not require creative efforts. The communication line can be a wire, a set of wires, a bus, a track, a wireless communication line (inductive, radio frequency, infrared, ultrasonic, etc.). Communication protocols over communication lines are known to those skilled in the art and are not specifically disclosed.

The functional connection of elements should be understood as a connection that ensures the correct interaction of these elements with each other and the implementation of one or another functionality of the elements. Specific examples of functional communication can be communication with the ability to exchange information, communication with the ability to transmit electric current, communication with the ability to transmit mechanical movement, communication with the ability to transmit light, sound, electromagnetic or mechanical vibrations, etc. The specific type of functional relationship is determined by the nature of the interaction of these elements, and, unless otherwise indicated, is provided by widely known means using principles widely known in the art.

The design of the elements of the proposed device is known to specialists in this field of technology and is not described separately in this document, unless otherwise indicated. The elements of the device can be made of any suitable material. These component parts can be manufactured using known methods, including, by way of example only, machining, investment casting, crystal growth. Assembly, joining, and other operations in accordance with the above description also correspond to the knowledge of a person skilled in the art and, therefore, will not be explained in more detail here.

While exemplary embodiments have been described in detail and shown in the accompanying drawings, it should be understood that such embodiments are illustrative only and are not intended to limit the present invention, and that the present invention should not be limited to the specific arrangements and structures shown and described, since to a person skilled in the art, based on the information set forth in the description and knowledge of the prior art, various other modifications and embodiments of the invention may be apparent without departing from the spirit and scope of the invention.

Claims (31)

1. A device for transmitting signals, containing: - a waveguide containing: a first conductive base and a second conductive base parallel to each other, and located between the first conductive base and the second conductive base side walls containing at least one structure of the type of electromagnetic crystal with a band gap (EBG structure); and - at least two directional antennas located opposite each other along the radiation axis, each antenna is made on the basis of a printed circuit board and contains: An EBG structure located on the top and bottom layers of the printed circuit board and configured to prevent back radiation, and at least one matching element; wherein at least part of each of the antennas is located inside the waveguide, so that it completely covers the area between the antennas, forming in this area a wireless channel for transmitting electromagnetic signals, wherein said at least one matching element is located near the wireless channel and is configured to match the antenna with the wireless channel. 2. The device according to claim. 1, in which the EBG-structure contains a plurality of cells located next to each other in the form of a two-dimensional periodic lattice, and each cell contains: parallel conductive portions within the first and second conductive layers of the printed circuit board, and a conductive element passing through the thickness of the dielectric layer of the printed circuit board and connecting said conductive portions to each other; wherein at least within one of the first and second conductive layers of the printed circuit board, said conductive portions of adjacent cells are not electrically connected to each other. 3. The device according to claim 2, in which the EBG structure is separated from at least one of the bases by a dielectric gap, the device additionally contains: spacers located between the EBG structure and the base in the region of the said gap, which fix the EBG structure and provide the said gap, while the spacers are located so as not to close adjacent cells of the EBG structure with each other. 4. The apparatus of claim. 3, wherein the spacers are conductive, wherein the distance from the spacers to the boundary between the EBG structure and said wireless channel is more than three cells of the EBG structure. 5. The device according to claim. 2, in which the conductive element of the EBG-structure cell is made in the form of a through metallized hole (VIA), and the conductive section of the EBG-structure cell is made in the form of a contact pad. 6. The device according to claim. 2, in which at least one of the antennas contains within the multilayer printed circuit board at least two EBG structures and a SIW waveguide (implemented in the printed circuit board a waveguide with pin walls), enclosed between the at least two EBG structures, moreover, the conductive sections of adjacent cells of EBG structures within those conductive layers of the printed circuit board that form the upper and lower bases of the SIW waveguide are electrically connected to each other, the conductive sections of adjacent cells of EBG structures within the outermost conductive layers of the printed circuit board are not electrically connected to each other. 7. The apparatus of claim. 6, wherein at least part of the EBG structures of the sidewalls of the waveguide and said at least one of the antennas constitute a single EBG structure within a single printed circuit board. 8. The apparatus of claim. 1, wherein at least part of the waveguide and at least one of the antennas are integrated into a single printed circuit board. 9. The apparatus of claim. 1, in which the antennas are configured to transmit and receive through the wireless channel two types of waves, perpendicular to each other. 10. The device according to claim. 1, in which at least one of the antennas comprises a coiled patch antenna integrated into the printed circuit board, which is powered by a microstrip waveguide. 11. The device according to claim 1, wherein at least one of the antennas comprises a dipole antenna integrated into the printed circuit board. 12. The device of claim. 1, in which the antennas are located in the waveguide in such a way that the axis of radiation is parallel to the bases. 13. The device according to claim. 1, in which the antennas are located in the waveguide in such a way that the axis of radiation is perpendicular to the bases. 14. The apparatus of claim 13, wherein the first waveguide base, side walls and at least one of the antennas are integrated into the first printed circuit board, and the second base and at least one other of the antennas are integrated into the second printed circuit board. 15. The device of claim 13, wherein the side walls comprise at least two EBG structures and further comprise a conductive plate comprising a cutout in the region of the wireless channel, the first waveguide base, at least one of the EBG structures of the side walls and at least one of the antennas are integrated into the first printed circuit board, and the second base, at least one other of the EBG side wall structures and at least one other of the antennas are integrated into the second printed circuit board. 16. The apparatus of claim 13, wherein the side walls comprise a plurality of EBG structures located one above the other and separated from one another by conductive plates not in contact with the EBG structures.

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