Wireless communication system and receiving device

Abstract

To transmit a plurality of types of signals with a simple device configuration.SOLUTION: A radio communications system transmits a signal using electric field coupling caused by closely arranging a transmission coupler included in a first device and a reception coupler included in a second device. The second device includes a reception circuit connected to the reception coupler. The reception circuit has termination resistance larger than 10 / ωC, where C is coupling capacitance between the transmission coupler and the reception coupler and ω is a fundamental angular frequency of the signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for transmitting multiple types of signals. [Background technology]

[0002] Harnesses and cables are usually used as a means for connecting communication interfaces in multiple modules or multiple electronic devices. By making the parts where harnesses and cables are used wireless, there are advantages such as improving the assembly of products and facilitating the automation of manufacturing processes.

[0003] Patent Document 1 discloses a wireless communication system that transmits digital signals of "1" and "0" in a non-contact manner using electric field coupling. In Patent Document 1, wireless communication is realized using electric field coupling that occurs when couplers (hereinafter, couplers) provided in each of the transmitter and receiver are arranged facing each other and close to each other. Electric field coupling has characteristics similar to an HPF (high pass filter), which has a weak degree of coupling in low frequencies and a high degree of coupling in wide frequencies. Therefore, when the termination resistance of the circuit immediately after the coupler on the receiver side is set to 50Ω as in Patent Document 1, the waveform generated at the coupler on the receiver side becomes an imperfect differential waveform as described in Patent Document 1. In Patent Document 1, this imperfect differential waveform is shaped into digital signals of "1" and "0" by a hysteresis circuit (a comparator circuit with a threshold value) to perform wireless communication.

[0004] On the other hand, the USB (Universal Serial Bus) interface, which is one of the communication standards, is widely used mainly in personal computers (PCs), and various USB-compatible devices equipped with the USB interface are commercially available. In order to suppress power consumption accompanying an increase in communication speed, the USB 3.0 standard and subsequent standards stipulate that communication should be performed using normal data signals and LFPS (Low Frequency Periodic Signaling) signals. The normal data signal is a binary digital signal of 5 Gbps or more, and the LFPS signal is a ternary signal in an electrically idle state and a signal that periodically repeats "1" and "0" at 10 to 55 MHz. Since the method disclosed in Patent Document 1 assumes binary digital signal transmission, it is difficult to directly apply the method to a ternary LFPS signal for communication.

[0005] As a technique for dealing with such problems, Patent Document 2 describes a transmission device technique for wirelessly transmitting two types of signals: a normal data signal and an LFPS signal. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-29785 A [Patent Document 2] JP 2016-72790 A Summary of the Invention [Problem to be solved by the invention]

[0007] The transmission device disclosed in Patent Document 2 is configured to include two detection units for detecting normal data signals and LFPS signals, respectively, and an output control unit that controls the output of an output signal based on the detection results by the two detection units. Thus, in Patent Document 2, two detection units and an output control unit are required to transmit two types of signals, normal data signals and LFPS signals, resulting in a complex configuration. Therefore, there is a problem in that the circuit scale increases in order to transmit the two types of signals.

[0008] The present invention has been made in view of the above circumstances, and has as its object to transmit a plurality of types of signals using a simple device configuration. [Means for solving the problem]

[0009] As one means for achieving the above object, the wireless communication system of the present invention has the following configuration: Is electromagnetic 1. A wireless communication system for transmitting signals using field coupling, comprising: The first device transmits power of a power supply voltage conforming to the Universal Serial Bus (USB) standard to the second device; The second device comprises: A binary data signal with a fundamental frequency of 2.5 GHz and a ternary Low Frequency Periodic Signaling (LFPS) signal of 10-50 MHz are received via the receiving coupler. Receiving circuit an amplifier circuit connected to the receiving circuit; The receiving circuit has a coupling capacitance between the transmitting coupler and the receiving coupler, C, Binary data with a fundamental frequency of 2.5GHz If the fundamental angular frequency of the signal is ω, then a termination resistor larger than 10 / ωC is required. The amplifier circuit amplifies the binary data signal and the LFPS so that the amplification degree of a signal including a frequency of 10-50 MHz among the signals output from the receiver circuit is greater than the amplification degree of a signal including a frequency of 2.5 GHz. . Effect of the Invention

[0010] According to the present invention, it is possible to transmit a plurality of types of signals with a simple device configuration. [Brief description of the drawings]

[0011] [Figure 1] 1 shows an example of the configuration of a wireless communication system. [Diagram 2] 2 shows an example of the configuration of a first receiving circuit (High-Z differential amplifier circuit). [Diagram 3]Simulation results (when transmitting a 10MHz LFPS signal) are shown. [Figure 4] Simulation results (when transmitting a data signal at 5 Gbps) are shown. [Diagram 5] 11A and 11B are diagrams illustrating a correction function for a voltage amplitude on the low frequency side. [Figure 6] 2 shows another example of the configuration of a wireless communication system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0013] [First embodiment] (Configuration of wireless communication system) 1(a) to 1(c) show an example of the configuration of a wireless communication system 100 according to this embodiment. The wireless communication system 100 includes a first communication module 110 and a second communication module 120.

[0014] 1(a) in the wireless communication system 100 includes transmitting couplers 111a and 111b and a transmitting circuit 112, and the second communication module 120 includes receiving couplers 121a and 121b, a first receiving circuit (High-Z differential receiving circuit) 125, an amplifier circuit (AMP) 126, and a second receiving circuit 124. In the following description, the transmitting couplers 111a and 111b may be collectively referred to as transmitting couplers 111, and the receiving couplers 121a and 121b may be collectively referred to as receiving couplers 121.

[0015] In this embodiment, from the viewpoint of transmitting differential signals, each communication module has two couplers composed of two separated conductors. The coupler pattern is formed, for example, by a pattern of a rigid board or a flexible board, sheet metal, MID (Molded Interconnect Device) method, or the like. The transmitting coupler 111 of the first communication module 110 and the receiving coupler 121 of the second communication module 120 are disposed close to each other and facing each other, and are coupled by electromagnetic coupling. The wireless communication system 100 realizes wireless communication (signal transmission) between the first communication module 110 and the second communication module 120 using this electromagnetic coupling.

[0016] The transmitting circuit 112 is provided in a transceiver IC (Integrated Circuit) 114, and has a function of shaping the waveform of a signal input from a device such as a PC (Personal Computer) via a transmission medium such as a USB cable so as to satisfy the USB 3.0 standard and outputting the signal. The transceiver IC 114 may also be called a re-driver, and may be any circuit capable of transmitting and receiving signals having a waveform within a range defined by the USB 3.0 or later standard, and is not limited to a specific configuration. The second receiving circuit 124 is provided in a transceiver IC 127, and has a function of receiving an analog signal transmitted wirelessly, shaping the waveform of the signal to a device such as a camera via a transmission medium such as a board or a USB cable so as to satisfy the USB 3.0 standard, and outputting the signal as a digital signal. The transceiver IC 127 may also be called a re-driver, and may be any circuit capable of transmitting and receiving signals having a waveform defined by the USB 3.0 or later standard, and is not limited to a specific configuration, like the transceiver IC 114.

[0017] Fig. 1(b) and Fig. 1(c) show modified examples of the wireless communication system 100 shown in Fig. 1(a). Fig. 1(b) shows a configuration in which an amplifier circuit is provided as an amplifier circuit 113 on the first communication module 110 side, not on the second communication module 120 side. Fig. 1(c) shows a configuration in which an amplifier circuit is provided as an amplifier circuit 113 and an amplifier circuit 126 on both the first communication module 110 and the second communication module 120. The reason for providing an amplifier circuit is to make the voltage amplitude of the low-frequency LFPS signal equal to or greater than a predetermined value (so as to fall within a voltage range defined by the standard), as will be described later.

[0018] (Principle of LFPS signal transmission) Next, the principle by which the wireless communication module shown in Fig. 1 can transmit a ternary LFPS (Low Frequency Periodic Signaling) signal will be described with reference to the wireless communication system 100 shown in Fig. 1(a). First, a brief description of the LFPS signal will be given. The signal generated by the transmission circuit 112 has three values: "1", "0" and "idle" (indicating an electrically idle state). The USB3.0 standard specifies that Polling.LFPS and Ping.LPS periodically repeat a period during which a burst-like clock signal is output and a period (state) of "idle" during which nothing is output.

[0019] Fig. 2(a) shows the configuration of the first receiving circuit 125 in the wireless communication system 100 shown in Fig. 1(a). The flow of signal transmission of the LFPS signal is as follows. Either a signal "1" or "0" is generated in the transmitting circuit 112 and transmitted to the transmitting coupler 111. The signal is transmitted to the receiving coupler 121 by coupling between the couplers and then input to the first receiving circuit 125.

[0020] In this case, if the impedance of the first receiving circuit 125 is 50Ω, the impedance of the capacitive component caused by the coupling between the transmitting coupler 111 and the receiving coupler 121 is smaller in the low frequency range and larger in the high frequency range, compared to the input impedance of the first receiving circuit 125, 100Ω (50Ω×2). Therefore, the output waveform of the receiving coupler 121 becomes a differentiated waveform in which only high frequencies have passed. In other words, "0" or "1" becomes "0+idle" or "1+idle", making accurate transmission difficult.

[0021] In order to accurately transmit a ternary signal, the configuration described in Patent Document 2 is also conceivable, but as described above, the circuit scale of this configuration is large. Therefore, in this embodiment, in order to receive an LFPS signal and a 5 Gbps data signal in the same circuit, the termination resistor Rrx connected between the input terminals of the first receiving circuit 125 is controlled. Specifically, when the coupling capacitance between the transmitting coupler 111 and the receiving coupler 121 is C, Rrx is set to be 10 / ωC or more. Here, ω is the fundamental angular frequency of the signal (baseband signal to be transmitted) and is calculated at 2.5 GHz. By selecting the input impedance of the receiving circuit in this way, it is possible to realize a reduction in the circuit scale and simplification.

[0022] (Differential receiver circuit configuration) FIG. 2 shows an example of the first receiving circuit 125 in this embodiment. The first receiving circuit 125 shown in FIG. 2 is a differential amplifier circuit. The two input terminals of the first receiving circuit 125 are connected to the receiving couplers 121a and 121b, respectively, and a resistor Rrx is connected between the terminals. A DC potential is supplied to the two input terminals of the first receiving circuit 125 from a bias circuit (not shown). Furthermore, a resistive element or the like may be inserted between the input terminals of the first receiving circuit 125 and the receiving couplers 121a and 121b. In the differential amplifier circuit, a current flows through a load resistor connected to the collector side according to the potential difference between the differential input terminals, and an output voltage is generated. Therefore, since the first receiving circuit 125 becomes an inverting amplifier circuit, it is necessary to switch the outputs of the inverting terminal and the non-inverting terminal, but since there is no potential difference between the differential pair during idle, three-value transmission is possible.

[0023] FIG. 3 shows the simulation results in this embodiment. Specifically, FIG. 3 shows waveforms at each measurement point during transmission of a 10 MHz LFPS signal when the coupling capacitance between the couplers is 0.22 pF, the coupling capacitance between the transmission couplers 111a and 111b is 0.35 pF, and the coupling capacitance between the reception couplers 121a and 121b is also 0.35 pF. FIG. 3(a) shows the voltage signal Vi input to the transmission coupler 111, and FIG. 3(b) shows the output voltage signal Vo when the input impedance of the first reception circuit 125 is 100 kΩ. FIG. 3(c) shows the waveform of the output voltage signal Vo when the input impedance of the first reception circuit 125 is 1 MΩ. By comparing the waveforms of the voltage signals in FIG. 3(b) and FIG. 3(c), it can be seen that, for a 10 MHz LFPS signal, if the input impedance of the first reception circuit 125 is sufficiently high, three-value transmission is possible.

[0024] Although a differential amplifier circuit as shown in FIG. 2 is shown as an example of the first receiving circuit 125, the first receiving circuit 125 is not limited to a differential amplifier circuit, and for example, a common collector circuit called an emitter follower circuit can also be used.

[0025] Also, the transmission flow of a 5 Gbps data signal is the same as that of an LFPS signal. Figure 4 shows the simulation results of eye patterns when a 5 Gbps data signal is transmitted. Figure 4(a) shows the eye pattern when the input impedance of the first receiving circuit 125 is 10 kΩ, and Figure 4(b) shows the eye pattern when the input impedance of the first receiving circuit 125 is 1 MΩ. It can be seen from Figure 4 that when the input impedance of the first receiving circuit 125 is 10 kΩ, there is some degradation in the waveform compared to when it is 1 MΩ, but even at about 10 kΩ, a sufficient eye opening can be obtained.

[0026] As described above, from the simulation results of FIG. 3 and FIG. 4, it can be seen that by using the configuration of this embodiment, it is possible to wirelessly transmit two types of signals, a 5 Gbps digital signal and a ternary LFPS signal of 10 to 50 MHz.

[0027] In the example of Fig. 3, the coupling capacitance between the couplers is set to 0.22 pF, but if the mounting area of ​​the couplers or the distance between the couplers needs to be increased, the signal amplitude will be small. In the USB 3.0 standard, the voltage amplitude of the LFPS signal needs to be 300 mVpp or more, so the output signal needs to be amplified. Therefore, as shown in the wireless communication system 100 of Figs. 1(a) to (c), by providing an amplifier circuit for reception (Fig. 1(a)), transmission (Fig. 1(b)), or both transmission and reception (Fig. 1(c)), the voltage amplitude can be amplified to a level that satisfies the standard.

[0028] If the input impedance of the first receiving circuit 125 cannot be made sufficiently high for the impedance due to the coupling capacitance between the couplers at a frequency of 10 to 50 MHz, the voltage amplitude of the output LFPS signal will have a waveform as shown in FIG. 3(b). In order to maintain 300 mVpp or more for 10 to 50 MHz, it is also preferable to amplify the signal amplitude with the amplifier circuit 126 as described above, taking the wireless communication system 100 shown in FIG. 1(a) as an example. However, if the voltage tolerance of the input terminal of the amplifier circuit 126 or the transceiver IC 127 connected after the first receiving circuit 125 is low, a protection diode (protection circuit) may be provided at the output of the first receiving circuit 125. FIG. 2(b) shows an example in which a protection diode is provided at the output of the first receiving circuit 125. In this way, the spike amount (spike voltage) can be mitigated by providing a protection diode or setting the set current of the current source in FIG. 2(a) so that the output cannot be 20% or more of 300 mVpp.

[0029] [First Modification] As mentioned above, it was found that the output voltage waveform differs when the input impedance of the first receiving circuit 125 is 100 kΩ and 1 MΩ. Also, from Fig. 4, it was found that, although there was some degradation in the waveform when the input impedance of the first receiving circuit 125 was 10 kΩ (Fig. 4(a)) and 1 MΩ (Fig. 4(b)), a sufficient eye opening could be obtained even at about 10 kΩ.

[0030] Thus, there is a discrepancy between the input impedance required for the first receiving circuit 125 during LFPS signal transmission and 5 Gbps data signal transmission. In other words, the first receiving circuit 125 needs to receive an LFPS signal of 10 to 50 MHz with an impedance of about 1 MΩ, and receive an impedance of about 10 kΩ in the 200 to 5 GHz band required for transmitting a 5 Gbps data signal. The reason is that the capacitive coupling between the couplers behaves like a high-pass filter, so low-frequency components are difficult to pass, so reception must be performed with a higher impedance, but high-frequency components pass easily, so a relatively low impedance is sufficient.

[0031] Considering this, the input impedance of the first receiving circuit 125 may be configured to have frequency characteristics. In general, it is difficult to ensure a uniform impedance of about 1 MΩ for frequencies up to 5 GHz on an FR4 board. However, it is possible to realize an impedance of about 1 MΩ for low frequencies of about 10 to 50 MHz. In this way, changing the input impedance of the first receiving circuit 125 according to the frequency of the signal received by the receiving coupler 121 is suitable as a means for realizing a 10 to 50 MHz LFPS signal and a 5 Gbps data signal using the same coupler and circuit, and can simplify the structure.

[0032] [Second modified example] Instead of changing the input impedance of the first receiving circuit 125 according to the frequency as in the first modification, a similar effect can be obtained by performing a correction to increase the voltage amplitude on the low frequency side. The correction can be realized by each circuit means such as the transmitting amplifier circuit 113 and the receiving amplifier circuit 126.

[0033] The correction function will be described with reference to Fig. 5. Fig. 5(a) shows the frequency characteristics of the transfer characteristic from the transmitting circuit 112 to the first receiving circuit 125 when the coupling capacitance between the couplers is 0.22 pF, the coupling capacitance between the transmitting couplers 111a and 111b and the coupling capacitance between the receiving couplers 121a and 121b are 0.35 pF, and the input impedance of the first receiving circuit 125 is 10 kΩ. Fig. 5(a) shows that the frequency band of 100 MHz or more is almost flat and transferable. However, at frequencies below 100 MHz, the gain decreases almost linearly.

[0034] Fig. 5(b) shows the frequency characteristic of the correction for the low-gain band shown in Fig. 5(a), which has a characteristic for amplifying signals in a frequency band of about 2 MHz to 100 MHz. By providing a correction circuit (amplifier circuit 126, etc.) having such a characteristic on the receiving side, LFPS signals on the low frequency side of 10 to 50 MHz among the received signals can be accurately identified. In other words, it becomes possible to reliably transmit low-frequency LFPS signals of 10 to 50 MHz even when the impedance of the first receiving circuit 125 is set within the range that can be realized by the FR4 board.

[0035] In addition, such a low-frequency correction function may be provided on the transmitting side (i.e., correction of the low-frequency signal among the signals to be transmitted by the amplifier circuit 113, etc.), in which case there is an advantage such as improved noise resistance.

[0036] [Third modified example] FIG. 6 shows a configuration example of a wireless communication system 600 in the third modified example. The wireless communication system 600 can realize wireless communication of USB 3.0 with a simple configuration. When the device side does not have a battery or the like and requires a power supply, the host side can supply power such as VBUS contactlessly. In that case, since there is a possibility of receiving electromagnetic interference from contactless power transmission, it is possible to avoid the interference by using a filter for the carrier frequency of contactless power transmission, such as a high pass filter (HPF) or a band stop filter (BSF), thereby making it possible to make the wireless communication system more reliable. In addition, it is also possible to ensure backward compatibility by using it together with a wireless module for USB 2.0.

[0037] [Other embodiments] The wireless communication system in the above embodiment has been described as a wireless communication system that transmits differential baseband signals, but the present invention is not limited to this and may be a wireless communication system that transmits a single signal.

[0038] Although the wireless communication system in the above embodiment is a system that is assumed to be compatible with USB 3.0 or later standards, the wireless communication system can be applied to systems that use ternary signals, not just USB. For example, the wireless communication system can be applied to systems that use Serial ATA (SATA) signals.

[0039] Furthermore, the above wireless communication system can wirelessly connect a USB cable that connects a personal computer to an electronic device, and can be applied to USB communication between a personal computer and a camera or between a personal computer and a printer, for example.

[0040] As described above, according to the above embodiment, it is possible to provide a wireless communication system capable of transmitting multiple types of signals, with a simple configuration and a size that can be implemented in small products and small-scale production facilities.

[0041] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0042] 100 wireless communication system, 110 first communication module, 120 second communication module, 111 transmission coupler, 121 reception coupler, 112 transmission circuit, 124 second reception circuit, 125 first reception circuit (High-Z differential reception circuit)

Claims

1. A wireless communication system in which a transmitting coupler included in a first device and a receiving coupler included in a second device transmit signals using electromagnetic coupling, The first device transmits power of a power supply voltage conforming to the Universal Serial Bus (USB) standard to the second device; The second device comprises: a receiving circuit that receives a binary data signal having a fundamental frequency of 2.5 GHz and a ternary Low Frequency Periodic Signaling (LFPS) signal of 10-50 MHz via the receiving coupler; an amplifier circuit connected to the receiving circuit, the receiving circuit has a termination resistance larger than 10 / ωC, where C is a coupling capacitance between the transmitting coupler and the receiving coupler, and ω is a fundamental angular frequency of the binary data signal having a fundamental frequency of 2.5 GHz; The amplifier circuit amplifies the binary data signal and the LFPS so that the amplification degree of a signal including a frequency of 10-50 MHz among the signals output from the receiver circuit is greater than the amplification degree of a signal including a frequency of 2.5 GHz.

1. A wireless communication system comprising:

2. the second device has a re-driver connected between the receiving circuit and the amplifier circuit; 2. The wireless communication system according to claim 1, wherein the redriver performs waveform shaping on the signal output from the receiving circuit and outputs the signal.

3. the second device has an amplifier circuit connected to the receiving circuit and a re-driver connected to the amplifier circuit; 2. The wireless communication system according to claim 1, wherein the re-driver performs waveform shaping on the signal output from the amplifier circuit and outputs the result from the second device.

4. 4. The wireless communication system according to claim 1, wherein the receiving circuit is further configured to mitigate spike voltages in the output signal.

5. 5. The wireless communication system according to claim 1, wherein the receiving circuit is configured such that an input impedance of the receiving circuit varies depending on the frequency of the signal received by the receiving coupler.

6. The wireless communication system according to any one of claims 1 to 5, characterized in that the first device has a transmitting side amplifier circuit connected to the transmitting coupler, and the transmitting side amplifier circuit amplifies the voltage amplitude of a signal having a frequency of 10 to 50 MHz among the frequencies of the signal to be transmitted.

7. 7. The wireless communication system according to claim 1, wherein the receiving circuit is a differential amplifier circuit.

8. 8. The wireless communication system according to claim 1, wherein the first device and the second device transmit and receive signals defined in a standard after USB 3.

0.

9. 8. The wireless communication system according to claim 1, wherein the first device and the second device transmit and receive signals defined by a Serial ATA standard.

10. A receiving device, a receiving coupler that receives a signal by using electromagnetic coupling with a transmitting coupler provided in a transmitting device; a receiving circuit that receives a binary data signal having a fundamental frequency of 2.5 GHz and a ternary Low Frequency Periodic Signaling (LFPS) signal of 10-50 MHz via the receiving coupler; an amplifier circuit connected to the receiving circuit, the receiving circuit has a termination resistance larger than 10 / ωC, where C is a coupling capacitance between the transmitting coupler and the receiving coupler, and ω is a fundamental angular frequency of the binary data signal having a fundamental frequency of 2.5 GHz; The amplifier circuit amplifies the binary data signal and the LFPS so that the amplification degree of a signal including a frequency of 10-50 MHz among the signals output from the receiver circuit is greater than the amplification degree of a signal including a frequency of 2.5 GHz. A receiving device comprising:

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