Wireless communication system

Abstract

The present invention relates to a system for short-range radio frequency communication between a main module and a plurality of detachable slave modules. The communication system includes a main wire connected to the main module and having a plurality of coupling points, characterized in that the communication system includes a plurality of secondary wires, each secondary wire having a first coupling region for directional coupling between the secondary line and the main line at the coupling point and a second coupling region for directional coupling between the secondary line and the slave module, the second coupling region being different from the first coupling region.

Description

Technical Field

[0001] The present invention relates to a short-range radio communication system that allows a device to communicate with multiple removable modules via a wireless link. The present invention can be particularly applied to a modular human-machine dialogue system, which includes multiple dialogue units that communicate with a main module. These various dialogue units are, for example, buttons or switches, visual or auditory signal units (lights, buzzers, etc.), sensors or detectors, etc. Background Art

[0002] Documents EP2479646 and EP2781993 have described a modular system in which multiple slave human-machine dialogue units can communicate with a main module. These dialogue units are designed to be mounted on a support module that can communicate with the main module. The dialogue units are removably and interchangeably mounted, which makes the solution easy to upgrade.

[0003] The link between the slave module and the support module is wired, while the link between the support module and the main module can be wired or wireless (via radio waves). However, the solutions described in these documents require the use of an intermediate support module, and in the case of a wireless link, especially when the dialogue unit is mounted on a metal housing, radio waves are generated that are subject to interference. In addition, there may also be mutual interference between multiple modular systems or between multiple slave modules.

[0004] Other solutions, especially those based on NFC, RFID, or Wilkinson power divider technology, are considered too expensive and bulky for such applications, and / or when a large number of slave modules need to be managed, its data rate may be too low.

[0005] Therefore, one of the objectives of the present invention is to find a simple, space-saving, and economical solution for enabling multiple slave modules to communicate directly with the main module via a wireless link, that is, without electrical contact. The number of slave modules is advantageously variable, that is, one or more slave modules can be very easily removed, replaced, or added at any time.

[0006] Another objective of the present invention is to greatly limit the range of wireless communication to avoid interference of this communication system with the environment, especially interference with the environment through the transmission of radio waves, to avoid its interference by the environment (such as a transmitter that may be located nearby (such as a Wi-Fi transmitter)), and also to avoid interference between two systems when placed side by side. Summary of the Invention

[0007] To this end, the present invention describes a system for radio frequency communication between a main module and a plurality of detachable slave modules. The communication system includes a main wire connected to the main module and having a plurality of coupling points, characterized in that the communication system includes a plurality of secondary wires, each secondary wire having a first coupling region for directional coupling between the secondary line and the main line at the coupling point, and a second coupling region for directional coupling between the secondary line and the slave module, the second coupling region being different from the first coupling region.

[0008] According to one feature, the first coupling region and the second coupling region of each secondary line are in a straight line shape or have a sawtooth shape.

[0009] According to another feature, each secondary line has two terminators, and the line-end impedance of the terminator is equal to the characteristic impedance of the secondary line. The main line is connected to the main module at one end and to a line-end impedance suitable for matching the characteristic impedance of the main line at the other end.

[0010] According to another feature, the main line and the secondary lines are conductive tracks integrated in the same main printed circuit board. According to another feature, the main line and the secondary lines are located in the same plane of the main printed circuit board.

[0011] According to another feature, the communication system further includes a plurality of slave modules, and one slave module includes an auxiliary printed circuit board provided with conductive tracks, and when the slave module communicates with the main module, the auxiliary printed circuit board is located above the main printed circuit board, opposite to the second coupling region.

[0012] According to another feature, the lengths of the first coupling region and the second coupling region depend on the operating frequency of the radio line.

[0013] According to another feature, the directional coupling at the first coupling region and the second coupling region is capacitive coupling and inductive coupling. Description of the Drawings

[0014] Other features will become apparent from the following detailed description given with reference to the accompanying drawings, in which:

[0015] - Figure 1 Shows a simplified diagram of the communication system according to the present invention.

[0016] - Figure 2 Shows in detail a cross-sectional view along the axis X of the coupling between the main line and the secondary lines.

[0017] - Figure 3 Shows in detail a cross-sectional view along the axis Y of the coupling between the secondary line and the slave module.

[0018] -Figure 4 Shows an alternative shape of the secondary line.

[0019] - Figure 5 Shows an alternative shape of the main line. Detailed implementation

[0020] Reference Figure 1 , in the case of an automated application, the purpose of the short - range radio frequency communication system is to enable the main module 10 to communicate with a plurality of slave modules 11, 11'. The main module 10 can be, for example, an automated device of the programmable logic controller or microcontroller type, which has electronic components (or chips) for radio transmission / reception. The communication between the main module and the slave modules can be carried out according to various communication protocols, as long as these protocols have a sufficient data rate for the intended application and a transmission frequency that does not require too long a wire length. For example, protocols such as Bluetooth or Zigbee can be used, and the components of these protocols are inexpensive, such as BLE (Bluetooth Low Energy) components. The slave modules 11, 11' are, for example, human - machine dialogue units of the button or switch type, visual or auditory signal units (lights, buzzers, etc.) and / or sensors or detectors, which also have components for radio transmission / reception.

[0021] Generally, it is necessary to upgrade the automated application by changing or adding human - machine dialogue units, for example, according to the needs of the user client. Moreover, for various reasons, especially for maintenance reasons, it is advantageous to be able to replace one unit with another.

[0022] In order to obtain such a modular, upgradable and easily modifiable system, the slave modules are detachably mounted and connected, that is, the slave modules can be easily removed, replaced or added without disturbing the wireless communication between the main module 10 and other slave modules. Similarly, by the solution adopted in the present invention, the presence or absence of the slave module 11 in a position has no effect on the communication between other slave modules and the main module 10.

[0023] To this end, the communication system includes a main electrical transmission line 1, which is connected on one side to the radio components of the main module 10 soldered on the printed circuit board 5 (for example, by means of metallized holes, called vias), and on the other side to a terminator impedance 9, especially for avoiding reflected radio waves. The main electrical transmission line 1 has a plurality of coupling points 2, 3, which are located at different positions along the main electrical transmission line 1. At Figure 1In order to simplify the illustration, only the first coupling point 2 and the second coupling point 3 are shown. The main electrical transmission line 1 is preferably made of a conductive track, which is placed inside a multilayer printed circuit board (or PCB: Printed Circuit Board), as described in detail below. The terminator impedance 9 is, for example, 50 ohms, and the main line must also have an exact characteristic impedance, typically 50 ohms. This characteristic impedance is basically determined by the width and thickness of the copper of the track and the width of the dielectric of the PCB and its dielectric constant.

[0024] Figure 5 Another embodiment of the main electrical transmission line 1 is shown, the main line having a U-shaped conductive track, the U-shaped conductive track having two sections connected together, the first end of the U being connected to the main module 10 and the other end of the U being connected to the terminator impedance 9. This allows more coupling points 2, 3, 2', 3' to be placed on the main electrical transmission line 1, and thus a larger number of slave modules can be connected in a smaller space. Obviously, other shapes of the main electrical transmission line 1 are easily conceivable.

[0025] The communication system also includes a plurality of secondary electrical transmission lines. Figure 1 The first secondary transmission line 20 and the second secondary transmission line 30 are shown. Each secondary transmission line has a first coupling region 21 (or 31), which allows for directional coupling with the main electrical transmission line 1 at the coupling point 2 (or 3).

[0026] Advantageously, the presence of secondary transmission lines that are not electrically connected to the main line (allowing radio communication to be transmitted between slave modules and the main module) provides a simple solution that can avoid mismatches in the main line (and thus potential performance instability or variations), depending on the number of slave modules connected to the communication system and their presence or absence.

[0027] Generally speaking, directional coupling is a passive device that transfers a portion of the signal propagating through the main transmission line to the secondary transmission line. In this document, the expression "directional coupling" is used to mean that the coupling for performing communication between two wires in close proximity to each other is carried out capacitively and inductively. These directional couplings are created by wires of, for example, the "microstrip" or preferably the "stripline" type.

[0028] In the illustrated embodiment, the main line and the secondary lines are preferably straight, substantially parallel to each other, and at a very small distance from each other at the coupling points 2, 3 and in the coupling regions 21, 31 in order to obtain good coupling. However, other shapes are possible in addition to the straight shape, such as zigzag or sawtooth, which would allow the geometric length of these regions to be limited while maintaining a satisfactory electrical length compatible with the wavelength used.

[0029] Figure 2 shows a cross-sectional view of a printed circuit board 5, referred to as the main printed circuit board, taken along the Figure 1 axis X at the coupling point 2. It can be seen that the coupling region 21 between the main electrical transmission line 1 and the first secondary transmission line 20 lies in the same horizontal plane of the printed circuit board 5. Advantageously, the main electrical transmission line 1, the first secondary transmission line 20, and the second secondary transmission line 30 are conductive tracks integrated in the same printed circuit board 5, which simplifies the manufacture of the communication system.

[0030] The main printed circuit board 5 is a multi-layer printed circuit board and consists of two outer conductive tracks 6, 7 made of copper, which are electrically connected to the zero potential (0V) of the printed circuit board to form a shield and thus limit the propagation of radio waves. The printed circuit board 5 also includes inner conductive tracks made of copper that form the main electrical transmission line 1, the first secondary transmission line 20, and the second secondary transmission line 30. The printed circuit board 5 can be made, for example, of a standard PCB with four conductive layers, by trimming one of the two inner copper layers from the four conductive layers, and wherein the thickness of the insulating layer, typically made of prepreg and epoxy resin, is adapted such that the remaining inner copper conductive tracks are located in the middle of the printed circuit board 5, that is, substantially in the middle between the outer conductive tracks 6 and 7. For example, the thickness of the outer conductive tracks can be 17 μm, while the thickness of the inner conductive tracks can be 35 μm, with the overall thickness of the printed circuit board being approximately 1.6 mm. Typically, at the coupling point 2, the first coupling region 21 has a length of, for example, 10 mm, and the distance d1 between the main electrical transmission line 1 and the first coupling region 21 of the first secondary transmission line 20 is, for example, 0.7 mm.

[0031] Each secondary transmission line also includes a second coupling region 22 (or 32), which allows for a directional coupling to be generated between the secondary line and the slave module 11 (or 11') when the slave module is present in the vicinity of the second coupling region.

[0032] Figure 3 shows a cross-sectional view of a printed circuit board 5, referred to as the main printed circuit board, taken along the Figure 1Cross-sectional view of the main printed circuit board 5 generated by the axis Y at the second coupling region 22 of the first secondary transmission line 20. Each slave module 11 includes a printed circuit board, referred to as an auxiliary printed circuit board, which has internal conductive tracks 12 that are preferably linear and are located between two insulating layers of substantially the same thickness and are made of prepreg and epoxy resin. A conductive layer 16 made of copper is placed on the upper part of the auxiliary printed circuit board 15 of the slave module 11. However, in order to ensure effective coupling between the internal conductive tracks 12 and the second coupling region 22, the lower part of the auxiliary printed circuit board 15 does not include a conductive layer. Similarly, the main printed circuit board 5 does not include an upper metal layer at the respective second coupling regions 22, 32 on a surface area of approximately 10 mm by 10 mm, and this surface area obviously depends on the size of the slave module.

[0033] Therefore, when it is desired to connect the slave module 11 to the main module 10, it is sufficient to simply place the slave module 11 on the main printed circuit board 5 such that the auxiliary printed circuit board 15 of the slave module 11 is directly above the second coupling region 22 of the first secondary transmission line 20, which allows the internal conductive tracks 12 of the auxiliary printed circuit board 15 to be coupled to the second coupling region 22 of the first secondary transmission line 20. Thus, the radio communication between the main module 10 and the slave module 11 will occur on the one hand through the directional coupling between the internal conductive tracks 12 and the second coupling region 22, and on the other hand through the directional coupling between the first coupling region 21 and the main electrical transmission line 1.

[0034] Figure 1 The internal conductive tracks 12 of the auxiliary printed circuit board 15 and the second coupling region 22 of the first secondary transmission line 20 are in two different planes, different from the Figure 1 disclosed in the simplified diagram showing the overview of the communication system, as Figure 2 and 3 clearly and detailedly shown, the main electrical transmission line 1 and the first coupling region 21 of the first secondary transmission line 20 are in the same plane.

[0035] Typically, the second coupling region 22 has a length of, for example, 10 mm, and the distance d2 between the second coupling region 22 and the internal conductive tracks 12 is, for example, approximately 1 mm. In addition, the conductive tracks of the first secondary transmission line 20 are preferably wider at the second coupling region 22. Generally speaking, obviously, the smaller the distance d2 and the greater the length and width of the second coupling region 22, the better the coupling will be. Therefore, these various parameters can be utilized to optimize the coupling relative to the existing dimensions and constraints.

[0036] In addition, in Figure 3In an embodiment, to further improve electrical continuity and compensate for the removal of the upper metal layer at the second coupling region 22, the slave module 11 may be mounted in a metal housing that is located on top of the auxiliary printed circuit board 15 and has two metal legs 18 in contact with the upper metal layer on both sides to form a shield when the slave module 11 is in place. The distance between the internal conductive track 12 and the slave module 11 may be approximately 5 mm, and the internal conductive track 12 is electrically connected to the radio components of the slave module 11, for example, by means of vias in the auxiliary printed circuit board. Embodiments in which a simple cut metal plate is used instead of the copper layer connected to 0V may also be considered.

[0037] Therefore, the coupling region serves as an antenna for radio transmission, and as a result, the communication between the master device and the slave device is kept maximally restricted at each coupling point and coupling region, especially through shielding; the communication system does not interfere with the environment and is not interfered with by the environment.

[0038] The slave modules 11, 11' can be powered by various devices (such as a battery / battery pack or a magnetic induction power supply) not described in detail in this document. Additionally, note that magnetic induction power supplies are mostly implemented at low frequencies, so they are far from the frequency band covered by the radio module (e.g., 2.4 GHz), and thus do not interfere with the communication system.

[0039] Each first secondary transmission line 20 must include terminators 28, 29 that are loaded with line end impedances equal to the characteristic impedance of the secondary line, such as 50 ohms, to avoid wave reflections within the transmission line. Figure 1 It is shown that each secondary line is made up of a plurality of straight segments connected end to end. In the described embodiment, it has been seen that the lengths of the first coupling region 21 and the second coupling region 22 are approximately 10 mm, and their widths are approximately 1 mm. Additionally, the wavelength for radio communication, i.e., the operating frequency of 2.4 GHz in the described embodiment, the thickness of the main printed circuit board 5, the dielectric parameters of the substrate, and the width of the coupling region must be taken into account to optimize the length of the second coupling region 22 of the first secondary transmission line 20. Generally, a total length of approximately 3 cm for the first secondary transmission line 20 gives satisfactory results.

[0040] The configuration of the segments of each secondary line can take various different shapes and especially depends on the space available for the printed circuit board 5 and the optimization of various couplings. Figure 4 An alternative first secondary transmission line 20 is shown, in which one of the terminal segments 27 forms an acute angle with the first coupling region 21 instead of being at a right angle as in Figure 1 the embodiment, which has the advantage of increasing the potential space for other electrical tracks (not covered by this communication system) on the same PCB printed circuit board.

Claims

1. A system for radio frequency communication between a main module (10) and a plurality of detachable slave modules (11, 11'), the communication system comprising a main line (1) connected to the main module and having a plurality of coupling points (2, 3). Characterized in that the communication system comprises a plurality of secondary lines (20, 30), each secondary line having a first coupling region (21, 31) for directional coupling between the secondary line and the main line (1) at the coupling points (2, 3) and a second coupling region (22, 32) for directional coupling between the secondary line and the slave module (11, 11'), the second coupling region (22, 32) being different from the first coupling region (21, 31). the main line (1) and the secondary lines (20, 30) are conductive tracks integrated in the same main printed circuit board (5). It further comprises a plurality of slave modules, one slave module (11) comprising an auxiliary printed circuit board (15) provided with conductive tracks (12), and when the one slave module (11) communicates with the main module (10), the auxiliary printed circuit board is located above the main printed circuit board (5) and opposite to the second coupling region (22).

2. The communication system according to claim 1, Characterized in that the shapes of the first coupling region (21, 31) and the second coupling region (22, 32) of each secondary line (20, 30) are linear.

3. The communication system according to claim 1, Characterized in that the first coupling region (21, 31) or the second coupling region (22, 32) of each secondary line (20, 30) has a sawtooth shape.

4. The communication system according to claim 1, Characterized in that each secondary line (20) has two terminators, and the line-end impedance (28, 29) of the terminators is equal to the characteristic impedance of the secondary line (20).

5. The communication system according to claim 1, Characterized in that one end of the main line (1) is connected to the main module (10), and the other end is connected to a line-end impedance (9) designed to match the characteristic impedance of the main line (1).

6. The communication system according to claim 1, Characterized in that the main line (1) and the secondary lines (20, 30) are located in the same plane as the main printed circuit board (5).

7. The communication system according to claim 1, Characterized in that the lengths of the first coupling region (21, 31) and the second coupling region (22, 32) depend on the operating frequency of the radio line.

8. The communication system according to claim 1, Characterized in that the main module and the slave module communicate with each other through the Zigbee protocol or the Bluetooth protocol.

9. The communication system according to any one of the preceding claims, Characterized in that the directional coupling at the first coupling region and the second coupling region is capacitive coupling and inductive coupling.

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