Wireless communication system, receiving device, control method, and program

Abstract

To allow a received signal that can be used for demodulation processing to be stably obtained.SOLUTION: A wireless communication system includes: a transmitting device including at least two transmitting transmission paths in which at least one of signal feed points or terminal points is arranged opposite to each other, and transmitting means for inputting a signal to each of the feed points of the at least two transmitting transmission paths; a receiving device including a receiving transmission path that moves along the at least two transmitting transmission paths, electromagnetically couples with the transmitting transmission paths, and receives an excited signal, and output means that receives signals from one end and the other end of the receiving transmission path, and outputs a signal to be subject to demodulation processing based on the received signals.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wireless communication system including a movable transmission path, a receiving device, a control method, and a program. [Background technology]

[0002] In recent years, technologies have been disclosed for performing cable-less data communication via a rotating movable part to solve problems such as tangled cables when controlling devices having rotating movable parts, such as robotic hands and network cameras, through communication over a network.

[0003] For example, Patent Document 1 describes an invention of a device that transmits a wideband signal between at least two units that can move relative to each other along an arbitrary track by non-contact electromagnetic signal coupling. This device includes two conductor structures (transmission transmission paths) that extend in opposite directions on the track of the units with a power supply point of a transmission signal from a transmitter T1 as a boundary, and two directional couplers (reception transmission paths) that receive a signal flowing through the conductor structures. The two directional couplers are arranged so that their signal output ends face each other along the track, and in this arrangement, they move along the track on the conductor structures to receive the signal flowing through the conductor structures by electromagnetic signal coupling in a non-contact manner. The two signals received by the two directional couplers are either combined or switched to one of the signals by a changeover switch in the subsequent stage and output to a demodulator or the like. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2003-533114 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technology of Patent Document 1, there are cases where both the power supply points and the termination points of two conductor structures are arranged close to each other and facing each other on a unit having a closed orbit of a rotating system. In this case, two directional couplers move from one conductor structure to the other conductor structure across the two opposing power supply points or termination points. During this movement, there are cases where neither the signals received by the two directional couplers nor the combined signal obtained by combining these signals can be used for demodulation processing of the transmission signal. Therefore, an object of the present invention is to stably obtain a received signal that can be used for demodulation processing even when the receiving transmission path moves across the opposing power supply points or termination points of two transmitting transmission paths. [Means for solving the problem]

[0006] In order to solve the above problem, a wireless communication system according to one embodiment of the present invention includes a transmission transmission path consisting of at least two transmission paths in which at least one of the signal feed points or end points is arranged opposite to each other, a transmission means for inputting a signal to each of the feed points of the transmission transmission paths, a reception transmission path that moves along the transmission transmission path, electromagnetically couples with the transmission transmission path, and receives an excited signal, and an output means for receiving signals from one end and the other end of the reception transmission path, and outputting a signal to be subjected to demodulation processing based on the received signal. Effect of the Invention

[0007] According to the present invention, a received signal that can be used for demodulation processing can be stably obtained even when the receiving transmission line moves across two opposing power supply points or two termination points of two transmitting transmission lines. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a first configuration example of a wireless communication system according to a first embodiment. [Diagram 2] 2 is a diagram showing an example of transition of the moving position of the reception transmission path in FIG. 1; [Diagram 3]3 is a timing chart of signals of each component at each movement position in FIG. 2; [Figure 4] FIG. 2 is a diagram showing a second configuration example of the wireless communication system according to the first embodiment. [Diagram 5] 5 is a diagram showing an example of transition of the moving position of the reception transmission path in FIG. 4. [Figure 6] 5 is a timing chart of signals of each component at each movement position in FIG. 4. [Figure 7] FIG. 13 is a diagram showing a third configuration example of the wireless communication system according to the first embodiment. [Figure 8] FIG. 11 is a schematic diagram showing a configuration example of a wireless communication system according to a second embodiment. [Figure 9] 9 is a diagram showing an example of transition of the moving position of the reception transmission path in FIG. 8; [Figure 10] FIG. 13 is a schematic diagram illustrating a configuration example of a wireless communication system according to a third embodiment. [Figure 11] FIG. 13 is a perspective view showing an example of a substrate structure of a transmission and reception transmission path according to a fourth embodiment. [Figure 12] 12 is a cross-sectional view showing an example of a combination of substrate structures related to the transmission and reception transmission paths of FIG. 11. [Figure 13] 13 is a diagram showing frequency characteristics of signals in each combination example of FIG. 12. [Figure 14] 13 is a diagram showing the time characteristics of signals in each combination example of FIG. 12. [Figure 15] FIG. 13 is a perspective view showing an example of a substrate structure of a transmission and reception transmission path according to a fifth embodiment. [Figure 16] 16 is a cross-sectional view showing an example of a combination of substrate structures related to the transmission and reception transmission paths of FIG. 15. [Figure 17] 17A and 17B are diagrams showing frequency characteristics of signals in the example combinations of FIGS. 16A and 16B. [Figure 18] 17 is a diagram showing the time characteristics of signals in each combination example of FIG. 16. [Figure 19] FIG. 23 is a cross-sectional view showing an example of a substrate structure of a transmission and reception transmission line according to a sixth embodiment. [Figure 20] 20 is a diagram showing frequency characteristics of a signal in the example of the board structure of FIG. 19. [Figure 21]20 is a diagram showing time characteristics of signals in the example of the board structure of FIG. 19. [Figure 22] FIG. 1 is a system configuration diagram for explaining a principle common to each embodiment. [Diagram 23] 4 is a timing chart for explaining a principle common to each embodiment. [Figure 24] FIG. 1 is a schematic diagram for explaining the operation of a conventional technique. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the embodiment described below is one example of a means for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the device to which the present invention is applied and various conditions, and the present invention is not limited to the embodiment described below. (Explanation of the receiving transmission path principle) Before describing the embodiments of the present invention, first, a description will be given of the coupled end and isolated end of a receiving transmission line and the signal characteristics of each component, which are a principle common to all the embodiments.

[0010] 22(a) and (b) are diagrams for explaining a coupled end and an isolated end of a receiving transmission line in a wireless communication system, and FIG. 23(a) and (b) are timing charts of signals of each component in the wireless communication system of FIG. 22(a) and (b). 22(a) includes a transmitting device 100 and a receiving device 200. The transmitting device 100 includes a transmitting transmission path 101, a signal source 102, and a differential transmitting buffer 103. The receiving device 200 includes a receiving transmission path 201 and a comparator 202. The transmission line 101 is composed of a differential line, one end of which receives a differential signal from a differential transmission buffer 103 and the other end of which is terminated by a terminating resistor.

[0011] The receiving transmission line 201 is composed of a differential line, and the end on the same side as the terminated side of the transmitting transmission line 101 is terminated by a termination resistor. The receiving transmission line 201 moves along the transmitting transmission line 101 on the transmitting transmission line 101, and receives a signal excited by electromagnetic field coupling with the transmitting transmission line 101 in a non-contact (wireless) manner. In other words, the receiving transmission line 201 constitutes a directional coupler. In this way, the output end of the signal of the receiving transmission line 201 when the end on the same side as the terminated side of the transmitting transmission line 101 is terminated is called a coupled end.

[0012] On the other hand, the wireless communication system shown in Fig. 22(b) has a configuration in which the signal output end and the terminated end of the receiving transmission line 201 are reversed in the wireless communication system shown in Fig. 22(a). That is, the end of the sending transmission line 101 opposite to the terminated end is terminated by a termination resistor, and the signal output end of the receiving transmission line 201 in this case is called an isolation end.

[0013] In Figures 23(a) and (b), the horizontal axis is time and the vertical axis is voltage. In addition, common to the wireless communication systems of Figures 22(a) and (b), OUT0 is the output signal of the signal source 102, SIG1 is a signal in the vicinity of the receiving transmission path 201 of the transmitting transmission path 101, and SIG2 is a signal detected in the receiving transmission path 201. Also, Com0 is the output signal of the comparator 202 in Figure 24(a), and Com1 is the inverted output signal of the comparator 202 in Figure 22(b).

[0014] As shown by the signal SIG2 in Fig. 23(a), when a signal is output from the coupled end, the output signal from the receiving transmission line 201 becomes an edge signal with a pulse width of a time period corresponding to the length L1 of the receiving transmission line 201. On the other hand, as shown by the signal SIG2 in Fig. 23(b), when a signal is output from the isolated end, the output signal from the receiving transmission line 201 becomes an inverted edge signal with a very short pulse width. (Problems with the prior art) Next, in order to clarify the problems with the conventional technology, the operation of the conventional technology of Patent Document 1 will be described with a concrete example. 24(a), (b), (c) and (d) are diagrams for explaining the operation of a wireless communication system according to the conventional technology.

[0015] 24(a) to (d), the wireless communication system according to the conventional technology includes a transmitting device 300 and a receiving device 400. The transmitting device 300 includes transmission transmission paths 301 and 302, a signal source 303, and a transmission buffer 304. The receiving device 400 includes reception transmission paths 401 and 402, a first comparator 403, a second comparator 404, and a change-over switch 405. The transmission transmission paths 301 and 302 are arranged in a ring shape, with their respective signal input ends, that is, their power supply points, and their respective termination points, that is, the other ends terminated by termination resistors, arranged close to and facing each other.

[0016] The receiving transmission paths 401 and 402 are composed of two transmission paths whose signal output ends are close to each other and face each other. The receiving transmission paths 401 and 402 are configured so that the combined length of both paths, including the opposing gap portions, is shorter than the length of the transmitting transmission paths 301 and 302. The receiving transmission paths 401 and 402 move along the transmitting transmission paths 301 and 302 and receive signals flowing through the transmitting transmission paths 301 and 302 in a non-contact manner by electromagnetic signal coupling.

[0017] As shown in Fig. 24(a) to (d), the receiving device 400 is configured so that the receiving transmission lines 401 and 402 move clockwise along the transmitting transmission lines 301 and 302. In the movement from Fig. 24(a) to (b), the output of the receiving transmission line 401 becomes an output as a coupled end, and an edge pulse having a time length according to the length of the receiving transmission line 401 is obtained. On the other hand, the output of the receiving transmission line 402 becomes an output as an isolated end while the receiving transmission line 401 is on the transmitting transmission line 301, and a signal having a sign inverted from that of the coupled end is output for a short time.

[0018] After that, when the receiving transmission line 402 starts to overlap the transmitting transmission line 302, the output of the receiving transmission line 402 becomes a signal that is a combination of the signal component as the isolated end and the signal component as the coupled end. Then, at the position of FIG. 24(b), the output of the receiving transmission line 402 becomes a signal only as the coupled end.

[0019] 24(b) to (c), the output of the receiving transmission line 402 becomes an output as a coupled end, and an edge pulse with a time length according to the length of the receiving transmission line 402 is obtained. On the other hand, the output of the receiving transmission line 401 becomes a signal that is a combination of a signal component as an isolated end and a signal component as a coupled end when the receiving transmission line 402 starts to overlap with the transmitting transmission line 302. Thereafter, the output of the receiving transmission line 401 becomes a signal only as an isolated end when the receiving transmission line 401 moves onto the transmitting transmission line 302.

[0020] 24(a) to (c), at least one of the receiving transmission lines 401 and 402 outputs a signal as a coupled end. Therefore, in the moving position of FIG. 24(b), the changeover switch 405 can be used to switch to the output signal of the coupled end.

[0021] On the other hand, when moving from FIG. 24(c) to FIG. 24(d), the output of the receiving transmission line 401 becomes the output as an isolated end. On the other hand, the output of the receiving transmission line 402 becomes the combined output of the signal component as a coupled end and the signal component as an isolated end, and becomes the output only as an isolated end at the moving position of FIG. 24(d). Therefore, whether the outputs of the receiving transmission lines 401 and 402 are switched or combined, the output component as an isolated end becomes larger than the output component as a coupled end somewhere between FIG. 24(c) and FIG. 24(d). Therefore, the sign of the edge signal is inverted, and neither of the output signals of the receiving transmission lines 401 and 402 can be used for demodulation processing of the signal input to the sending transmission lines 301 and 302. In this way, during the movement from FIG. 24(c) to (a), no output can be obtained from the coupled end, causing a problem that normal signal reception is not possible. (First embodiment) Next, a first embodiment of the present invention will be described below. Figures 1 to 7 are diagrams showing the first embodiment. [First configuration example] FIG. 1 is a diagram illustrating a first configuration example of a wireless communication system according to a first embodiment. As shown in FIG. 1, a wireless communication system 1 according to the first configuration example includes a transmitting device 10A and a receiving device 20. The transmitting device 10A includes transmission transmission lines 11 and 12, termination resistors 13 and 14, a signal source 15, and differential transmission buffers 16 and 17.

[0022] The transmission transmission lines 11 and 12 are each composed of a differential line of equal length, and the power supply points, which are the input ends of the respective signals, are disposed close to and facing each other. Termination resistors 13 and 14, which have approximately the same characteristic impedance as the transmission transmission line 11, are electrically connected to the other ends of the transmission transmission lines 11 and 12 opposite the power supply points. In other words, the other ends of the transmission transmission lines 11 and 12 terminated by the termination resistors 13 and 14 constitute the termination points of the signals.

[0023] The signal source 15 outputs a signal corresponding to transmission data (hereinafter referred to as a "transmission signal"). The differential transmission buffers 16 and 17 are each electrically connected to the signal source 15, and amplify the transmission data signal input from the signal source 15 and convert it into a differential signal. In other words, the differential transmission buffers 16 and 17 output the amplified signal directly from one of the two output terminals, and output the amplified signal with its sign inverted from the other terminal.

[0024] One of the two output terminals of the differential transmit buffer 16 is electrically connected to one feed point of the differential line of the transmission transmission line 11, and the other is electrically connected to the other feed point of the differential line of the transmission transmission line 11. In addition, one of the two output terminals of the differential transmit buffer 17 is electrically connected to one feed point of the differential line of the transmission transmission line 12, and the other is electrically connected to the other feed point of the differential line of the transmission transmission line 12.

[0025] In the wireless communication system 1 of FIG. 1, the differential transmission buffers 16 and 17 and the signal source 15 are connected directly by signal lines, but this is not the only possible configuration. For example, a resistive divider or a Wilkinson divider (both not shown) may be inserted to divide a high-frequency signal from the signal source 15. By dividing the signal using these dividers, the signal is input to the differential transmission buffers 16 and 17 at the same timing with impedance matching. Therefore, the same signal can be input to each of the power feed points of the transmission transmission lines 11 and 12 at the same timing. This makes it possible to prevent a situation in which a signal on one transmission transmission line is delayed relative to a signal on the other transmission transmission line, even when the reception transmission line 21 spans two opposing power feed points. On the other hand, the receiving device 20 includes a receiving transmission line 21 , combiners 22 and 23 , a differential filter 24 , and a comparator 25 . The receiving transmission line 21 is composed of a differential line and is shorter than the transmitting transmission lines 11 and 12. The receiving transmission line 21 is configured to receive, in a non-contact (wireless) manner, a signal excited by electromagnetic coupling with the transmitting transmission lines 11 and 12. Here, the electromagnetic field coupling includes coupling due to an electric field, coupling due to a magnetic field, and coupling due to both an electric field and a magnetic field.

[0026] The transmitting device 10A is disposed, for example, on a stationary structure (not shown), and the receiving device 20 is disposed, for example, on a structure (not shown) that moves back and forth in a straight line. In addition, the transmitting device 10A and the receiving device 20 are configured so that the receiving transmission path 21 can move back and forth along the transmitting transmission paths 11 and 12 at an opposing distance that allows electromagnetic field coupling. However, the present invention is not limited to this configuration, and as long as the receiving transmission path 21 moves along the transmitting transmission paths 11 and 12, the receiving device 20 may be disposed on a stationary structure while the transmitting device 10A is disposed on a structure that moves back and forth in a straight line.

[0027] A first output terminal 21a, which is one end of the differential lines constituting the receiving transmission line 21, is electrically connected to one input terminal of a combiner 22 whose differential input impedance is matched to an input impedance substantially equal to the differential impedance of the receiving transmission line 21. A second output terminal 21b, which is the other end of the differential lines constituting the receiving transmission line 21, is electrically connected to the other input terminal of the combiner 22.

[0028] The third output terminal 21c, which is the other end of the differential lines constituting the receiving transmission line 21, is electrically connected to one input terminal of the combiner 23, whose differential input impedance is matched to an input impedance substantially equal to the differential impedance of the receiving transmission line 21. The fourth output terminal 21d, which is the other end of the differential lines constituting the receiving transmission line 21, is electrically connected to the other input terminal of the combiner 23.

[0029] That is, the impedance of the lines between the first to fourth output terminals 21a to 21d of the receiving transmission line 21 and the combiners 22 and 23 is matched with the characteristic impedance of the receiving transmission line 21. This makes it possible to suppress the influence of reflected waves and reduce the transmission loss of signals from each output terminal of the receiving transmission line 21 to the combiners 22 and 23. The output terminal of the combiner 22 is electrically connected to one of the two input terminals of the differential filter 24, and the output terminal of the combiner 23 is electrically connected to the other of the two input terminals of the differential filter 24.

[0030] The combiner 22 combines signals received from a first output terminal 21a and a second output terminal 21b on one side of the differential lines constituting the receiving transmission line 21, and outputs this first combined signal to the differential filter 24. The combiner 23 combines signals received from a third output terminal 21c and a fourth output terminal 21d on the other side of the differential lines, and outputs a second combined signal obtained by inverting this combined signal to the differential filter 24. The differential filter 24 is a filter that suppresses the signal components at the isolation ends of the differential combined signal that is the output signal of the combiners 22 and 23. The differential filter 24 is formed of, for example, a low-pass filter. One of the two output terminals of the differential filter 24 is electrically connected to one of the two input terminals of the comparator 25, and the other of the two output terminals of the differential filter 24 is electrically connected to the other of the two input terminals of the comparator 25. The differential filter 24 outputs to the comparator 25 the first composite signal after filtering and a third composite signal obtained by inverting the second composite signal after filtering.

[0031] The comparator 25 detects the rising and falling edges of a difference signal, which is a signal of the signal level of the potential difference between the first and third composite signals input to the two input terminals. The comparator 25 is provided with hysteresis so that the detected edge signal outputs "1" when it is equal to or higher than a positive threshold voltage Vth, and outputs "0" when it is equal to or lower than a negative threshold voltage -Vth.

[0032] Specifically, after detecting the rising edge of the difference signal, the comparator 25 maintains "1" until the next falling edge is detected, and after detecting the falling edge of the difference signal, the comparator 25 maintains "0" until the next rising edge is detected. In this way, the transmission signal is demodulated by performing demodulation processing on the combined and filtered received signal.

[0033] 1, the ground serving as the reference potential of the transmitting transmission lines 11 and 12 and the receiving transmission line 21 is omitted, but each transmission line may be formed of, for example, a microstrip line, a coplanar line, or a coplanar line with a ground. In the first embodiment, the transmitting transmission lines 11 and 12 and the receiving transmission line 21 are formed of a microstrip line.

[0034] In addition, the transmission transmission lines 11 and 12 and the reception transmission line 21 are configured from differential lines, but are not limited to this configuration and may be configured from single-ended transmission lines. In this case, the differential transmission buffers 16 and 17 are replaced with single-ended transmission buffers. Also, only one of the combiners 22 and 23 is left, and the differential filter 24 is replaced with a single-ended filter. Fig. 2 is a diagram showing an example of transition of the moving position of the reception transmission path 21 of the wireless communication system 1 according to the first configuration example. Fig. 3(a), (b) and (c) are timing charts of signals of each component at each moving position (1), (2) and (3) in Fig. 2. 3(a) to 3(c), the horizontal axis is time and the vertical axis is voltage. In addition, in FIG. 3(a) to 3(c), the signals output from each component are essentially differential signals, but for convenience of explanation, they are shown as difference signals obtained by taking the potential difference between each differential signal.

[0035] 3(a) to 3(c), IN1 is a difference signal of the differential signals input to the power supply points of the transmission lines 11 and 12, respectively, and OUT1 is a difference signal of the differential signals output from the first output terminal 21a and the third output terminal 21c of the reception transmission line 21. Also, OUT2 is a difference signal of the differential signals output from the second output terminal 21b and the fourth output terminal 21d of the reception transmission line 21. Also, COUT is a difference signal of the differential composite signals output from the combiners 22 and 23, FOUT is a difference signal of the differential composite signals after filtering by the differential filter 24, and ComOUT is an output signal output from the comparator 25. As shown in FIG. 2, the receiving transmission path 21 moves linearly to transition between a first position (1), a second position (2), and a third position (3) relative to the sending transmission paths 11 and 12, as indicated by (1) to (3) in the figure. The first position (1) is a position where the entire receiving transmission path 21 is located on the transmitting transmission path 11, the second position (2) is a position where the receiving transmission path 21 straddles the power feed points of the transmitting transmission paths 11 and 12, and the third position (3) is a position where the entire receiving transmission path 21 is located on the transmitting transmission path 12. In the second position (2), the ends of the receiving transmission path 21 on the side of the first output terminal 21a and the third output terminal 21c are located on the transmitting transmission path 12, and the ends on the side of the second output terminal 21b and the fourth output terminal 21d are located on the transmitting transmission path 11.

[0036] 2, the differential output of the first output terminal 21a and the third output terminal 21c of the receiving transmission line 21 is an output as a coupled terminal. On the other hand, the differential output of the second output terminal 21b and the fourth output terminal 21d of the receiving transmission line 21 is an output as an isolated terminal.

[0037] At the first position (1), as shown in Fig. 3(a), the difference signal COUT of the differential combined signal output from the combiners 22 and 23 is reduced in size because the signal component at the isolated end is combined with the signal component at the coupled end near the center. Here, the signal width of the output signal at the isolated end is narrow and contains many high frequency components, so these components can be suppressed by a low-pass filter. In other words, a signal without a dip near the center is obtained as the difference signal FOUT after filtering by the differential filter 24. Subsequently, as a demodulation process, the comparator 25 detects the rising and falling edges of this signal, and the original transmission signal (input signal IN1) is demodulated as the output signal ComOUT.

[0038] 2, the differential output of the second output terminal 21b and the fourth output terminal 21d of the receiving transmission line 21 is an output as a coupled terminal, unlike the first position (1). Also, the differential output of the first output terminal 21a and the third output terminal 21c of the receiving transmission line 21 is an output as an isolated terminal.

[0039] That is, in the third position (3), as shown in FIG. 3(c), the difference signal OUT1 becomes equal to the difference signal OUT2 in FIG. 3(a), and the difference signal OUT2 becomes equal to the difference signal OUT1 in FIG. 3(a). That is, the difference signals OUT1 and OUT2 are reversed from those in the first position (1), but the difference signal COUT after combining these becomes the same signal. Therefore, this difference signal COUT is filtered by the differential filter 24, and the rising edge and falling edge of the filtered difference signal FOUT are detected by the comparator 25. As a result, the original transmission signal (input signal IN1) is demodulated as the output signal ComOUT.

[0040] 2, the first output end 21a and the third output end 21c of the receiving transmission path 21 are coupled ends with respect to the transmitting transmission path 11 and are isolated ends with respect to the transmitting transmission path 12. On the other hand, the second output end 21b and the fourth output end 21d of the receiving transmission path 21 are coupled ends with respect to the transmitting transmission path 12 and are isolated ends with respect to the transmitting transmission path 11.

[0041] That is, in the second position (2), as shown in FIG. 3(b), both of the difference signals OUT1 and OUT2 are signals in which the signal components as the coupled end and the signal components as the isolated end are combined. In this case, the difference signals OUT1 and OUT2 are output signals having a shorter pulse width and a larger ripple than the output signal as a normal coupled end. By filtering this output signal with the differential filter 24, a signal with a shorter pulse width than the difference signal FOUT of FIG. 3(a) and (c) is obtained as the difference signal FOUT with the ripple suppressed. The rising edge and the falling edge of the difference signal FOUT of the differential filter 24 are detected by the comparator 25. As a result, even when the receiving transmission line 21 moves across the power supply points of the transmitting transmission lines 11 and 12, the original transmitting signal (input signal IN1) is normally demodulated as the output signal ComOUT. [Second configuration example] Next, a second configuration example of the wireless communication system according to the first embodiment will be described. FIG. 4 is a diagram illustrating a second configuration example of the wireless communication system according to the first embodiment. The wireless communication system 2 according to the second configuration example includes a transmitting device 10B and a receiving device 20, as shown in FIG. The transmitting device 10B is configured such that the transmission transmission lines 11 and 12 of the transmitting device 10A of the first configuration example are arranged in the opposite directions and the end points are closely opposed to each other. The rest of the configuration, including the receiving device 20, is the same as the first configuration example. Fig. 5 is a diagram showing an example of transition of the moving position of the reception transmission path 21 of the wireless communication system 2 according to the second configuration example. Figs. 6(a), (b) and (c) are timing charts of signals of each component at each moving position (4), (5) and (6) in Fig. 5. In Figures 6(a) to (c), the horizontal axis is time and the vertical axis is voltage. In Figures 6(a) to (c), the signals output from each component are differential signals, but for convenience of explanation, they are referred to as difference signals. Each signal is a signal from the same component as in the first configuration example. As shown in FIG. 5, the receiving transmission path 21 moves linearly to a fourth position (4), a fifth position (5), and a sixth position (6) relative to the sending transmission paths 11 and 12, as shown by (4) to (6) in the figure. The fourth position (4) is a position where the entire receiving transmission path 21 is located on the transmitting transmission path 11, the fifth position (5) is a position where the receiving transmission path 21 straddles the end points of the transmitting transmission paths 11 and 12, and the sixth position (6) is a position where the entire receiving transmission path 21 is located on the transmitting transmission path 12. In the fifth position (5), the ends of the receiving transmission path 21 on the side of the first output terminal 21a and the third output terminal 21c are located on the transmitting transmission path 12, and the ends on the side of the second output terminal 21b and the fourth output terminal 21d are located on the transmitting transmission path 11.

[0042] 5, the differential output of the second output terminal 21b and the fourth output terminal 21d of the receiving transmission line 21 is an output as a coupled terminal. On the other hand, the differential output of the first output terminal 21a and the third output terminal 21c of the receiving transmission line 21 is an output as an isolated terminal.

[0043] In the fourth position (4), as shown in FIG. 6(a), the difference signal COUT of the differential combined signal output from the combiners 22 and 23 is combined with the signal component at the isolated end near the center of the signal component at the coupled end, making the output signal smaller. Here, the signal width of the output signal at the isolated end is narrow and contains many high frequency components, so these components can be suppressed by a low-pass filter. That is, a signal without a dip near the center is obtained as the difference signal FOUT after filtering by the differential filter 24. The rising and falling edges of this signal are detected by the comparator 25, and the original transmission signal (input signal IN1) is demodulated as the output signal ComOUT.

[0044] 5, the differential output of the first output terminal 21a and the third output terminal 21c of the receiving transmission line 21 is an output as a coupled terminal, unlike the fourth position (4). On the other hand, the differential output of the second output terminal 21b and the fourth output terminal 21d of the receiving transmission line 21 is an output as an isolated terminal.

[0045] In the sixth position (6), as shown in Fig. 6(c), the difference signals OUT1 and OUT2 are reversed from those in the fourth position (4), but the difference signal COUT of the differential composite signal output from the combiners 22 and 23 is the same as COUT in Fig. 6(a). Therefore, by detecting the rising and falling edges of this signal by the comparator 25, the original transmission signal (input signal IN1) is demodulated as the output signal ComOUT.

[0046] 5, the second output end 21b and the fourth output end 21d of the receiving transmission line 21 are on the transmitting transmission line 11 and serve as a coupled end for the transmitting transmission line 11 and an isolated end for the transmitting transmission line 12. On the other hand, the first output end 21a and the third output end 21c of the receiving transmission line 21 are on the transmitting transmission line 12 and serve as a coupled end for the transmitting transmission line 11 and an isolated end for the transmitting transmission line 12.

[0047] That is, at the fifth position (5), as shown in FIG. 6(b), both of the difference signals OUT1 and OUT2 are signals in which the signal components as the coupled end and the signal components as the isolated end are combined. In this case, the difference signals OUT1 and OUT2 are output signals having a shorter pulse width and a larger ripple before the rising edge of the signal than the output signal as a normal coupled end. By filtering this output signal with the differential filter 24, the ripple is suppressed as the filtered difference signal FOUT, and a signal having a shorter pulse width than the difference signal FOUT in FIG. 6(a) and (c) is obtained. The rising edge and falling edge of this difference signal FOUT are detected by the comparator 25. As a result, even when the receiving transmission line 21 moves across the two opposing end points of the sending transmission lines 11 and 12, the original sending signal (input signal IN1) is normally demodulated as the output signal ComOUT.

[0048] 3 and 6 show the demodulation of a signal (IN1) with a communication speed of 500 Mbps, and the signal width of the output signal FOUT of the differential filter 24 is 0.9 ns or more. Therefore, there is no need to use an expensive comparator with a small minimum pulse width.

[0049] Furthermore, consider a case where the ripple and noise level of the difference signal C of the composite signal is sufficiently smaller than the level of the difference signal C of the composite signal in Figures 3(a) and 3(c) and 6(a) and 6(c). In this case, the threshold of comparator 25 may be adjusted to be equal to or greater than the ripple and noise level of the difference signal C of the composite signal, thereby removing differential filter 24 from receiver 20. [Third configuration example] Next, a third configuration example of the wireless communication system according to the first embodiment will be described. FIG. 7 is a diagram illustrating a third configuration example of the wireless communication system according to the first embodiment. The wireless communication system 3 according to the third configuration example includes a transmitting device 10C and a receiving device 20, as shown in FIG.

[0050] The transmitting device 10C includes transmission lines 11a and 12a, transmission lines 11b and 12b, termination resistors 13a and 14a, and termination resistors 13b and 14b, a signal source 15, differential transmission buffers 16a and 17a, differential transmission buffers 16b and 17b, and distributors 18a, 18b, and 18c.

[0051] The transmission transmission paths 11a and 12a, and the transmission transmission paths 11b and 12b, respectively, have the same configuration as the transmission transmission paths 11 and 12 of the first configuration example. Moreover, the differential transmission buffers 16a and 17a, and the differential transmission buffers 16b and 17b, respectively, have the same configuration as the differential transmission buffers 16 and 17 of the first configuration example. The transmission transmission lines 11a and 12a are arranged such that their respective power feeding points are close to and face each other, and the other end of the transmission transmission line 11a is terminated by a termination resistor 13a, and the other end of the transmission transmission line 12a is terminated by a termination resistor 14a. The transmission transmission lines 11b and 12b are arranged such that their respective feeding points are close to and face each other, the other end of the transmission transmission line 11b is terminated by a termination resistor 13b, and the other end of the transmission transmission line 12b is terminated by a termination resistor 14b. The transmission transmission paths 11a and 12a, and the transmission transmission paths 11b and 12b are arranged such that the end point of the transmission transmission path 12a and the end point of the transmission transmission path 11b are adjacent to and face each other. As a result, three sets of transmission transmission lines are configured: two sets of transmission transmission lines whose power supply points face each other, and one set of transmission transmission lines whose end points face each other.

[0052] A data transmission signal (high frequency signal) from the signal source 15 is first divided into two by the divider 18a, one of which is further divided into two by the divider 18b and input to the power feed points of the transmission transmission lines 11a and 12a. The other of which is further divided into two by the divider 18c and input to the power feed points of the transmission transmission lines 11b and 12b. These dividers 18a to 18c are wired to have equal lengths so that the delay times from the signal source 15 to the differential transmission buffers are approximately equal. For example, a resistive divider or a Wilkinson divider can be used as the dividers 18a to 18c.

[0053] The transmitting device 10C is disposed, for example, on a stationary structure (not shown), and the receiving device 20 is disposed, for example, on a structure (not shown) that moves linearly. The receiving transmission path 21 is configured to be able to move back and forth along the transmitting transmission paths 11a and 12a and the transmitting transmission paths 11b and 12b at a distance that allows electromagnetic field coupling.

[0054] When the receiving transmission path 21 moves on the transmitting transmission paths 11a and 12a and on the transmitting transmission paths 11b and 12b, the operation is the same as that of the first configuration example (see Figs. 2 and 3). On the other hand, when the receiving transmission path 21 moves on the transmitting transmission paths 12a and 11b, the operation is the same as that of the second configuration example (see Figs. 5 and 6). Therefore, similarly to the above-mentioned first and second configuration examples, even if the receiving transmission path 21 moves so as to straddle two opposing power supply points or so as to straddle two opposing termination points, the original transmission signal (input signal IN1) can be demodulated normally. Here, also in the third configuration example, if the ripple and noise level of the output signals of the combiners 22 and 23 are sufficiently small, the threshold of the comparator 25 can be adjusted to be equal to or greater than the ripple and noise level of the output signals, thereby making it possible to remove the differential filter 24 from the receiving device 20.

[0055] In the above first to third configuration examples, the differential filter 24 is inserted between the combiners 22 and 23 and the comparator 25, but it may be inserted between the reception transmission path 21 and the combiners 22 and 23. Alternatively, the differential filter 24 may be inserted between the signal source 15 and the transmission transmission paths 11 and 12. In this case, the differential filter 24 may be inserted between the signal source 15 and the differential transmission buffers 16 and 17, or between the differential transmission buffers 16 and 17 and the transmission transmission paths 11 and 12. This makes it possible to suppress the ripple component of the transmission signal, and as a result, the signal component (ripple component) at the isolation end of the reception transmission path 21 is suppressed.

[0056] As described above, in the wireless communication systems 1 to 3 of the first embodiment, the transmitting devices 10A to 10C input signals from the signal source 15 to the respective feeding points of at least two transmitting transmission lines in which at least one of the feeding points or the end points of the signals is arranged opposite to each other. The receiving device 20 moves the receiving transmission line 21 along the transmitting transmission line and receives a signal excited by electromagnetic coupling with the transmitting transmission line. Furthermore, the combiners 22 and 23 receive signals from both one output end (the first output end 21a and the third output end 21c) and the other output end (the second output end 21b and the fourth output end 21d) of the receiving transmission line 21. The two received differential signals are combined by the combiners 22 and 23, respectively, and the combined signal is filtered by the differential filter 24 (low-pass filter). Then, the combined signal after filtering is output to the comparator 25 as a signal to be demodulated. With this configuration, even if the receiving transmission line moves across two opposing power feed points or two opposing termination points of the transmitting transmission line, a receiving signal that can be used for demodulation processing can be stably obtained. (Second embodiment) Next, a second embodiment of the present invention will be described below. Figures 8 and 9 are diagrams showing the second embodiment. The second embodiment differs from the first embodiment in that two transmission transmission lines are arranged in an annular shape, and their feed points and end points are arranged close to and opposite each other. Hereinafter, the differences from the first embodiment will be described in detail, and descriptions of overlapping parts will be omitted as appropriate. FIG. 8 is a schematic diagram illustrating a configuration example of a wireless communication system according to the second embodiment. The wireless communication system 4 according to the second embodiment includes a transmitting device 40 and a receiving device 50, as shown in FIG. The transmitting device 40 includes transmission lines 41 and 42, termination resistors 43 and 44, a signal source 45, and a transmitting buffer 46. The transmission lines 41 and 42 are of equal length and are each made up of a single-ended transmission line. Note that the transmission lines are not limited to a single-ended configuration and may be made up of a differential line.

[0057] One end of each of the transmission transmission lines 41 and 42 serves as a power supply point to which a signal is input, and is electrically connected to an output terminal of a transmission buffer 46. The other end of each of the transmission transmission lines 41 and 42 is electrically connected to a termination resistor 43 or 44 having substantially the same impedance as the characteristic impedance of the transmission transmission lines 41 or 42, forming a termination point.

[0058] The transmitter 40 is disposed on a circular stationary structure 600, and the transmission transmission paths 41 and 42 are arranged in a substantially circular shape along the circumferential direction on the outer circumferential surface of the stationary structure 600. Specifically, the transmission transmission paths 41 and 42 are each configured in a curved shape along the outer circumferential surface, and the power supply points of each path are arranged close to and opposite each other in the circumferential direction, and the end points of each path are arranged close to and opposite each other in the circumferential direction. An output terminal of the signal source 45 is electrically connected to an input terminal of a transmission buffer 46, and an output terminal of the transmission buffer 46 is electrically connected to the power supply points of the transmission transmission paths 41 and 42, respectively. The signal source 45 outputs a signal corresponding to the transmission data, and the transmission buffer 46 amplifies the transmission data signal input from the signal source 45 and inputs the amplified signal to the power supply points of the transmission transmission paths 41 and 42, respectively. The receiving device 50 includes a receiving transmission line 51 , a combiner 52 , and a comparator 53 .

[0059] The receiving transmission path 51 is composed of a single-ended transmission line, and is configured to be shorter than the transmitting transmission paths 41 and 42. A first output end 51a of the receiving transmission path 51 is electrically connected to one of two input terminals of a combiner 52, and a second output end 51b of the receiving transmission path 51 is electrically connected to the other of the two input terminals of the combiner 52. The output terminal of the combiner 52 is electrically connected to an input terminal of a comparator 53.

[0060] The receiving device 50 is disposed on a rotationally driven annular structure 601 (hereinafter referred to as the "rotating structure 601"), and the receiving transmission path 51 is disposed along the circumferential direction on the inner peripheral surface of the rotating structure 601. Specifically, the receiving transmission path 51 is configured in a curved shape along the inner peripheral surface.

[0061] 8, the stationary structure 600 and the rotating structure 601 are shown separately to clearly show the arrangement of the transmitting transmission lines 41 and 42 and the receiving transmission line 51, but in reality, the stationary structure 600 is arranged concentrically inside the rotating structure 601. The outer diameter of the stationary structure 600 and the inner diameter of the rotating structure 601 are each configured to be a diameter that allows the receiving transmission line 51 to move along the transmitting transmission lines 41 and 42 without contacting them when they are arranged concentrically, and provides an opposing distance that allows electromagnetic field coupling. The combiner 52 combines the signals input from the first and second output terminals 51a and 51b of the receiving transmission line 51, and outputs this combined signal to the comparator 53. The combiner 52 is matched to an input impedance that is approximately equal to the characteristic impedance of the receiving transmission line 51.

[0062] The comparator 53 detects the rising and falling edges of the input composite signal. The comparator 53 has a hysteresis function so that it outputs "1" when the detected edge signal is equal to or higher than the threshold voltage Vth, and outputs "0" when the detected edge signal is equal to or lower than the threshold voltage -Vth. 9(a), (b), (c) and (d) are diagrams showing examples of transition of the moving position of the receiving transmission path 51 in FIG. In the wireless communication system 4, as shown in FIGS. 9(a) to 9(d), a receiving transmission path 51 runs along and on the transmitting transmission paths 41 and 42 in a clockwise direction. In the example shown in FIG. 9, the receiving transmission path 51 is configured to rotate in a clockwise direction, but other operating patterns and operating ranges may be used, such as a configuration in which it rotates in a counterclockwise direction, or a configuration in which clockwise and counterclockwise movements are repeated alternately. In addition, since the receiving transmission path 51 only needs to move on and along the transmitting transmission paths 41 and 42, the receiving transmission path 51 may be arranged on the stationary structure 600 and the transmitting transmission paths 41 and 42 on the rotating structure 601 in the reversed configuration.

[0063] When the receiving transmission line 51 moves from the position in FIG. 9(a) through the position in FIG. 9(b) to the position in FIG. 9(c), the principle is the same as that of the first configuration example of the first embodiment. That is, at the moving position shown in FIG. 9(b), both of the output signals of the first and second output terminals 51a and 51b of the receiving transmission line 51 become signals in which the signal components as the coupled terminal and the signal components as the isolated terminal are combined. In this case, these combined signals become output signals with a shorter pulse width and larger ripple than the output signal as a normal coupled terminal. By detecting the rising edge and the falling edge of this combined signal by the comparator 53, the original transmission signal is normally demodulated as the output signal of the comparator 53 even when the receiving transmission line 51 moves across the power supply points of the transmitting transmission lines 41 and 42.

[0064] Also, when moving from the position of Fig. 9(c) through the position of Fig. 9(d) to the position of Fig. 9(a), the principle is the same as that of the second configuration example of the first embodiment. That is, at the moving position shown in Fig. 9(d), both of the output signals of the first and second output terminals 51a and 51b become signals in which the signal components as the coupled terminals and the signal components as the isolated terminals are combined. In this case, these combined signals become output signals with a shorter pulse width and larger ripples than the output signals as the normal coupled terminals, but they are signals that can be used sufficiently for demodulation processing. In other words, by detecting the rising and falling edges of this composite signal by the comparator 53, the original transmission signal is correctly demodulated as the output signal of the comparator 53 even when the receiving transmission path 51 moves across the termination points of the transmitting transmission paths 41 and 42. In the wireless communication system 4 shown in FIGS. 8 and 9, a filter (eg, a low-pass filter) for suppressing a signal component serving as an isolation end is not provided at the output stage of the combiner 52, but such a filter may be provided.

[0065] As described above, in the wireless communication system 4 of the second embodiment, the transmitter 40 is arranged in a circular shape, and inputs a signal from the signal source 45 to each of the feeding points of the transmission transmission lines 41 and 42, whose feeding points and end points are arranged opposite to each other. The receiver 50 moves the reception transmission line 51 along the transmission transmission lines 41 and 42, and receives a signal excited by electromagnetic coupling with the transmission transmission lines 41 and 42. Furthermore, the combiner 52 receives signals from both the first output end 51a and the second output end 51b of the reception transmission line 51, and combines the two received signals. The combined signal is then output to the comparator 53 as a signal to be demodulated. With this configuration, a received signal that can be used for demodulation processing can be stably obtained even if the receiving transmission path moves across two opposing power supply points or two termination points of two transmitting transmission paths. (Third embodiment) Next, a third embodiment of the present invention will be described with reference to Fig. 10, which shows the third embodiment.

[0066] The third embodiment is different from the first and second embodiments in that it has two change-over switches instead of a combiner, and the connection destination of the first and second output terminals of the receiving transmission line is switched to either a comparator or a termination resistor by controlling the switching operation of these two change-over switches. Hereinafter, differences from the first and second embodiments will be described in detail, and descriptions of overlapping parts will be omitted as appropriate. 10(a), (b), (c) and (d) are schematic diagrams showing an example of the configuration of a wireless communication system 5 according to the third embodiment and an example of transition of the moving position of a reception transmission path. The wireless communication system 5 includes a transmitting device 40 and a receiving device 60, as shown in FIGS. The receiving device 60 includes a receiving transmission line 61 , change-over switches 62 and 63 , a comparator 64 , and a termination resistor 65 . The transmitting device 40 is disposed on a stationary structure 600 as in the second embodiment, and the receiving device 60 is disposed on a rotating structure 601 as in the second embodiment.

[0067] The receiving transmission path 61 is composed of a single-ended transmission line, and is configured to be shorter than the sending transmission paths 41 and 42. The receiving transmission path 61 has one end, or a first output terminal 61a, electrically connected to one of the two input terminals of the change-over switches 62 and 63. The receiving transmission path 61 has the other end, or a second output terminal 61b, electrically connected to the other of the two input terminals of the change-over switches 62 and 63. An output terminal of the changeover switch 62 is electrically connected to an input terminal of the comparator 53 , and an output terminal of the changeover switch 63 is electrically connected to a termination resistor 65 . Although not shown in FIGS. 10(a) to 10(d), a control circuit for controlling the switching of the switches 62 and 63 is connected to the switches.

[0068] This control circuit controls the switching of the change-over switches 62 and 63 so that the output terminal having the longer time length (signal width) of the output signal out of the first output terminal 61a and the second output terminal 61b of the receiving transmission path 61 is connected to the comparator 64, and the output terminal having the smaller signal width is connected to the termination resistor 65. That is, the change-over switches 62 and 63 are controlled by the control circuit, so that when one output end of the receiving transmission path 61 is electrically connected to the comparator, the other output end is terminated. As a control method, for example, there is a method of detecting the signal widths of the output signals from the first output terminal 61a and the second output terminal 61b of the receiving transmission path 61, comparing the magnitudes (time lengths) of the detected signal widths, and switching the connection destination based on the comparison results. Also, for example, if the relationship between the moving position of the receiving transmission path 61 and the signal width of the output signal of the first output terminal 61a and the second output terminal 61b is known in advance, there is a method of detecting the moving position of the receiving transmission path 61 and switching the connection destination depending on the moving position. In either of the above control methods, basically, one output terminal having a larger signal width is connected to the comparator 64 , and the other output terminal is connected to the termination resistor 65 .

[0069] 10(b) and 10(d), the output signals of the first output terminal 61a and the second output terminal 61b have approximately the same signal width. That is, in the case of a control method in which switching is performed according to the moving position, it is determined in advance which of the first output terminal 61a and the second output terminal 61b is to be connected to the comparator 64 or the termination resistor 65. The control circuit may be configured as a circuit only, or may further include a processor and control the switching operations of the change-over switches 62 and 63 based on a control program executed by the processor.

[0070] Next, the operation of the third embodiment will be described based on Fig. 10 while referring to Fig. 3 and Fig. 6. Note that the signals obtained in the first and second configuration examples of the first embodiment (see Fig. 3 and Fig. 6) are slightly different from the signals obtained in the configuration example shown in Fig. 10, but have almost the same characteristics, so the description will be given with reference to these signals.

[0071] Hereinafter, the control circuit includes a sensor for detecting a rotation angle, and detects the moving position of the receiving transmission path 61 (the rotation position of the rotating structure 601) based on the detection value of this sensor. Then, the changeover switches 62 and 63 are switched based on the detected position information and a switching rule defined in advance according to the moving position. In addition, in the moving position shown in FIG. 10(b) where the output signals of the first output terminal 61a and the second output terminal 61b are both output signals of approximately the same signal width, the rule is set so that the second output terminal 61b is connected to the comparator 64 and the first output terminal 61a is connected to the termination resistor 65. Similarly, in the moving position shown in FIG. 10(d), the rule is set so that the first output terminal 61a is connected to the comparator 64 and the second output terminal 61b is connected to the termination resistor 65.

[0072] 10(a), the first output terminal 61a of the receiving transmission path 61 becomes a coupled terminal, and the second output terminal 61b becomes an isolated terminal. That is, the signal width of the output signal of the first output terminal 61a becomes larger than the signal width of the output signal of the second output terminal 61b (see FIG. 3(a)).

[0073] In this case, the control circuit controls the change-over switches 62 and 63 to connect the first output terminal 61a, which is a coupled terminal, to the comparator 64, and to connect the second output terminal 61b, which is an isolated terminal, to the termination resistor 65. By terminating the second output terminal 61b, the influence of reflected waves on the output signal from the first output terminal 61a can be suppressed. Furthermore, the original transmission signal is demodulated by detecting the rising and falling edges of the output signal output from the first output terminal 61a by the comparator 64.

[0074] Next, assume that the receiving transmission path 61 moves in the direction of the arrow in Fig. 10(a) from the moving position shown in Fig. 10(a) to the moving position shown in Fig. 10(b). In the moving position shown in Fig. 10(b), the first output end 61a of the receiving transmission path 61 is located on the sending transmission path 41, and the second output end 61b is located on the sending transmission path 42.

[0075] In this case, the output signals of the first output terminal 61a and the second output terminal 61b are both signals in which the signal components as the coupled terminal and the signal components as the isolated terminal are combined, and the signal width of both signals is approximately half the signal width of the output signal of the coupled terminal at the moving position of FIG. 10(a) (see FIG. 3(b)).

[0076] In this case, the control circuit controls the change-over switches 62 and 63 according to a predetermined rule to connect the second output terminal 61b to the comparator 64 and to connect the first output terminal 61a, which is the isolated terminal, to the termination resistor 65. This rule takes into consideration that the signal component of the coupled terminal becomes stronger as the signal component of the output signal of the second output terminal 61b by moving clockwise from the moving position shown in Fig. 10(b). The original transmission signal is demodulated by detecting the rising and falling edges of the output signal output from the second output terminal 61b by the comparator 64.

[0077] Next, assume that the receiving transmission line 61 moves in the direction of the arrow in Fig. 10(b) from the moving position shown in Fig. 10(b) to the moving position shown in Fig. 10(c). In the moving position shown in Fig. 10(c), the first output terminal 61a of the receiving transmission line 61 becomes an isolated terminal, and the second output terminal 61b becomes a coupled terminal. That is, the signal width of the output signal of the second output terminal 61b becomes larger than the signal width of the output signal of the first output terminal 61a (see Fig. 3(c)). Here, since it is only necessary to maintain the connection configuration switched to the movement position shown in FIG. 10(b), the change-over switches 62 and 63 are not switched and the connection configuration is maintained. The original transmission signal is demodulated by detecting the rising and falling edges of the output signal output from the second output terminal 61b by the comparator 64.

[0078] Next, assume that the receiving transmission line 61 moves in the direction of the arrow in Fig. 10(c) from the movement position shown in Fig. 10(c) to the movement position shown in Fig. 10(d). In the movement position shown in Fig. 10(d), the first output end 61a of the receiving transmission line 61 is located on the sending transmission line 42, and the second output end 61b is located on the sending transmission line 41.

[0079] In this case, the output signals of the first output terminal 61a and the second output terminal 61b are both signals in which the signal components as the coupled terminal and the signal components as the isolated terminal are combined, and the signal width of both signals is approximately half the signal width of the output signal of the coupled terminal at the moving position of FIG. 10(c) (see FIG. 6(b)).

[0080] In this case, the control circuit controls the change-over switches 62 and 63 according to a predetermined rule to connect the first output terminal 61a to the comparator 64 and to connect the second output terminal 61b, which is an isolated terminal, to the termination resistor 65. In this case, as in the case of the movement position shown in Fig. 10(b), the rule takes into consideration that the signal component of the coupled terminal becomes stronger as a signal component of the output signal of the first output terminal 61a by moving clockwise from the movement position shown in Fig. 10(d). The original transmission signal is demodulated by detecting the rising and falling edges of the output signal output from the first output terminal 61a by the comparator 64.

[0081] As described above, in the wireless communication system 5 of the third embodiment, the transmitter 40 is arranged in a circular shape, and inputs a signal from the signal source 45 to each of the feeding points of the transmission transmission lines 41 and 42, whose feeding points and termination points are arranged opposite to each other. The receiver 60 moves the reception transmission line 61 along the transmission transmission lines 41 and 42, and receives a signal excited by electromagnetic coupling with the transmission transmission lines 41 and 42. Furthermore, the control circuit controls the switching operation of the change-over switches 62 and 63. Specifically, the change-over switches 62 and 63 are controlled so that the end of the first output terminal 61a or the second output terminal 61b of the reception transmission line 61, which has a larger signal width of the output signal, is connected to the comparator 64, and the other end is connected to the termination resistor 65. With this configuration, even if the receiving transmission path 61 moves across two opposing power supply points or two termination points of the transmitting transmission paths 41 and 42, a receiving signal that can be used for demodulation processing can be stably obtained.

[0082] In the third embodiment, the change-over switches 62 and 63 are controlled in accordance with the movement position of the receiving transmission path 61 so that when the receiving transmission path 61 is moved to the movement position shown in Fig. 10(b), the second output terminal 61b is connected to the comparator 64 and the first output terminal 61a is connected to the termination resistor 65. In addition, when the receiving transmission path 61 is moved to the movement position shown in Fig. 10(d), the first output terminal 61a is connected to the comparator 64 and the second output terminal 61b is connected to the termination resistor 65. With this configuration, even if the receiving transmission line 61 moves around on the sending transmission lines 41 and 42, communication can be performed without interruption. (Fourth embodiment) Next, a fourth embodiment of the present invention will be described with reference to Figures 11 to 14, which show the fourth embodiment. In the fourth embodiment, the board structures and circuit configurations of the transmission transmission paths 41 and 42 and the reception transmission path 51 are partially different from those of the wireless communication system 4 in the second embodiment. Hereinafter, differences from the second embodiment will be described in detail, and descriptions of overlapping parts will be omitted as appropriate.

[0083] Here, when the receiving transmission line rotates, the combined signal may have large undershoot and overshoot, which may make it difficult to set the threshold value of the comparator. The fourth embodiment aims to make it easier to set the threshold value of the comparator by improving the substrate structure of at least one of the transmitting transmission line or the receiving transmission line to increase the difference between the output at the coupled end and the output at the isolated end of the receiving transmission line. Fig. 11(a) is a perspective view showing a substrate structure of transmission transmission paths 71 and 72 and a reception transmission path 51 of a wireless communication system 6 according to a fourth embodiment. Fig. 11(b) is a perspective view for explaining the substrate structure of the transmission transmission path 71 and the reception transmission path 51.

[0084] Fig. 12(a) is a diagram showing a first combination example of the substrate structure of the transmission transmission line and the reception transmission line, Fig. 12(b) is a cross-sectional view taken along line AA in Fig. 11(a) and shows a second combination example of the substrate structure of the transmission transmission line and the reception transmission line, Fig. 12(c) is a diagram showing a third combination example of the substrate structure of the transmission transmission line and the reception transmission line, and Fig. 12(d) is a diagram showing a fourth combination example of the substrate structure of the transmission transmission line and the reception transmission line. As shown in FIG. 11(a), a wireless communication system 6 includes a transmitting device 70 and a receiving device 50'. The transmitting device 70 includes transmitting transmission lines 71 and 72 , termination resistors 43 and 44 , a signal source 45 , and transmitting buffers 46 and 47 . The transmission buffer 46 amplifies the signal input from the signal source 45 and inputs the amplified signal to the power feed point of the transmission transmission path 71. In addition, the transmission buffer 47 amplifies the signal input from the signal source 45 and inputs the amplified signal to the power feed point of the transmission transmission path 72. The receiving device 50' has a configuration in which a filter 54 is inserted between the combiner 52 and the comparator 53 in the receiving device 50 of the second embodiment. The filter 54 is formed of, for example, a low-pass filter.

[0085] The receiving transmission path 51 includes a receiving substrate 51c, a line pattern 51d formed on one surface of the receiving substrate 51c, and a ground 51e formed on the other surface of the receiving substrate 51c. The line pattern 51d is a single-ended line pattern that serves as a signal transmission path, and the ground 51e is a conductive ground that serves as a reference potential for the receiving transmission path 51. That is, in the example shown in FIGS. 11(a) and (b), the receiving transmission line 51 is configured as a single-ended microstrip line. In the example shown in Figures 11(a) and (b), the line pattern 51d is formed along the longitudinal direction at the center of the width of the lower surface of the receiving substrate 51c, and the ground 51e is formed on the substrate surface so as to cover substantially the entire upper surface of the receiving substrate 51c. The transmission transmission path 71 includes a transmission board 71a, a line pattern 71b formed on one surface of the transmission board 71a, and a ground 71c formed on the other surface of the transmission board 71a. The transmission transmission path 72 includes a transmission board 72a, a line pattern 72b formed on one surface of the transmission board 72a, and a ground 72c formed on the other surface of the transmission board 72a. The line patterns 71b and 72b are single-ended line patterns that serve as signal transmission paths, and the grounds 71c and 72c are conductive grounds that serve as reference potentials for the line patterns 71b and 72b. In the example shown in FIGS. 11(a) and 11(b), the line patterns 71b and 72b are formed in the center in the width direction of the upper surfaces of the transmitting substrates 71a and 72a along the longitudinal direction.

[0086] On the other hand, as shown in Figures 11(a) and 11(b) and Figure 12(b), the ground 71c is configured to cover substantially the entire lower surface of the transmitting substrate 71a, and its cross section is configured to be substantially U-shaped. Specifically, the upper ends of both widthwise ends of the ground 71c are fixed to both widthwise ends of the lower surface of the transmitting substrate 71a. Note that the fixing position is not limited to this position, and it is preferable to fix it to a position that has little effect on the characteristic impedance of the transmission transmission path 71, such as a side position of the substrate. The other portion (surface portion) of the ground 71c other than both ends is disposed at a position separated from the other surface of the transmitting substrate 71a, and the surface facing the lower surface of the transmitting substrate 71a is disposed substantially parallel to the lower surface. The same configuration is also applied to the ground 72c. In addition, space 71d surrounded by ground 71c and the lower surface of transmitting substrate 71a, and space 72d surrounded by ground 72c and the lower surface of transmitting substrate 72a are filled with a material having a relative dielectric constant lower than the relative dielectric constants of transmitting substrates 71a and 72a, respectively. Specifically, the spaces 71d and 72d can be filled with a material having a lower relative dielectric constant than that of the transmitting substrates 71a and 72a, such as air, resin foam, or PTFE (polytetrafluoroethylene).

[0087] The transmitting boards 71a and 72a and the receiving board 51c can be made of a general electric board such as FR-4. FR-4 is an electric board made by soaking glass fiber cloth in epoxy resin and subjecting it to a heat curing process to form a plate, and has a relatively high relative dielectric constant.

[0088] Here, the line widths of the line patterns 71b and 72b and the line pattern 51d are set by the relative dielectric constants, board thicknesses, electrode thicknesses, characteristic impedances, and frequencies of the transmitting boards 71a and 72a and the receiving board 51c. Therefore, in order to obtain a desired characteristic impedance, when the relative dielectric constant of the board is relatively high, it is necessary to narrow the line width compared to when it is relatively low.

[0089] That is, only the board material such as FR-4 is between the line pattern 51d and the ground 51e, whereas the board material such as FR-4 and a layer of air are between the line patterns 71b and 72b and the grounds 71c and 72c. Therefore, the apparent relative dielectric constant on the transmitting side is lowered, and the transmitting transmission lines 71 and 72 can have a line width wider than that of the receiving transmission line 51 when the characteristic impedance is the same, for example, 50 [Ω], as shown in FIG. 12(b).

[0090] Figures 13(a), (b), (c), and (d) are diagrams showing frequency characteristics for a 2 [Gbps] transmission signal (input signal to the feeding point) in each of the combination examples in Figures 12(a) to (d). In Figures 13(a) to (d), the horizontal axis is frequency, the vertical axis is signal level [dB], the solid line is the signal level of the signal output from the coupled end with the transmission signal as a reference, and the dashed line is the signal level of the signal output from the isolated end with the transmission signal as a reference.

[0091] 12(a) is a first combination example for comparison with the second to fourth combination examples according to the fourth embodiment. Specifically, it is a combination example of a substrate structure in which the transmission transmission lines 41 and 42 and the reception transmission line 51 are each configured with a conventional microstrip line. That is, the transmission transmission lines 41 and 42 and the reception transmission line 51 are configured such that their respective grounds are provided on the substrate surface without being spaced apart from the substrate. Moreover, FIG. 12(b) shows a second combination example of the substrate structures shown in FIGS. 11(a) and (b), which is a combination example in which the substrate structure of the receiving transmission path 51 is combined with the substrate structures of the transmitting transmission paths 71 and 72 according to the fourth embodiment. FIG. 12(c) shows a third combination example in which the substrate structure of a receiving transmission path 81 in which the ground structure of the receiving transmission path 51 is made the same as the ground structure of the transmitting transmission path 71 instead of the receiving transmission path 51 is combined with the substrate structures of the transmitting transmission paths 41 and 42. Here, the receiving transmission path 81 includes a receiving substrate 81a, a line pattern 81b formed on one surface of the receiving substrate 81a, and a ground 81c formed on the other surface of the receiving substrate 81a.

[0092] The ground 81c has a structure similar to that of the ground 71c, and includes a space 81d surrounded by the top surface of the receiving substrate 81a and the ground 81c. Like the spaces 71d and 72d, the space 81d is filled with a material having a relative dielectric constant lower than that of the receiving substrate 81a. 12(d) shows a fourth combination example in which the substrate structure of the transmitting transmission paths 71 and 72 and the substrate structure of the receiving transmission path 81 are combined. Hereinafter, the frequency characteristics of the signals output from the two output terminals of the receiving transmission line at a maximum frequency of 1 [GHz] of the fundamental frequency of 2 [Gbps] data will be described. That is, the signal characteristics of "m1" and "m2" in Fig. 13 (a) to (d) will be described. First, the frequency characteristics when the combination of the substrate structures of the transmitting substrate and the receiving substrate is the first combination example shown in FIG. 12(a) will be described. In this case, the difference (hereinafter referred to as the "level difference") between the signal level of the output signal at the output end functioning as a coupled end of the receiving transmission path 51 and the signal level of the output signal at the output end functioning as an isolated end is approximately 6 dB, as shown in FIG. 13(a).

[0093] Next, the level difference between the output signal at the coupled end and the output signal at the isolated end of the receiving transmission lines 51 and 81 is calculated when the combination of the substrate structures is the second and third combination examples shown in Figures 12(b) and 12(c). The level difference between the two combination examples in this case is about 10 [dB], as shown in Figures 13(b) and 13(c). Next, when the combination of substrate structures is the fourth combination example shown in FIG. 12(d), the level difference between the output signal at the coupled end of the receiving transmission path 81 and the output signal at the isolated end is approximately 15 dB, as shown in FIG. 13(d). That is, it can be seen that by using the ground 71c or 81c structure for either the substrate structure of the transmitting transmission path or the substrate structure of the receiving transmission path, the level difference is increased by about 4 dB compared to the level difference in the conventional structure. On the other hand, it can be seen that by using the ground 71c or 81c for both the substrate structures of the transmitting transmission path and the receiving transmission path, the level difference is increased by about 9 dB compared to the conventional structure.

[0094] 14(a), (b), (c) and (d) are diagrams showing the signal waveforms of a composite signal obtained by combining output signals from both ends of a receiving transmission line when a 2 Gbps signal is transmitted using the transmission lines of the respective combination examples shown in FIG. 12(a) to (d). More specifically, the diagrams show the signal waveforms after filtering the ripple components of the composite signal.

[0095] 14(a)-(d), the horizontal axis is time, the vertical axis is voltage, IN2 is an input (transmitted) signal of 2 [Gbps], and FOUT2 is a filtered composite signal when the moving position of the receiving transmission line is 0 [mm] and -30 [mm]. In FIG. 14(a)-(d), the solid line waveform shows the filtered composite signal FOUT2 when the moving position is -30 [mm], and the dashed line waveform shows the filtered composite signal FOUT2 when the moving position is 0 [mm].

[0096] In the filtered waveforms, the waveform at -30 [mm] (solid line) is the signal when the entire receiving transmission line is located on one of the two transmitting transmission lines, and the waveform at 0 [mm] (dashed line) is the signal when the receiving transmission line is located exactly in the middle of the two transmitting transmission lines (a position straddling two opposing power supply points or two termination points).

[0097] As shown in Fig. 14(a) to (d), the waveforms at -30[mm] are signals in which the normal coupled end signal is slightly mixed with the isolated end signal, resulting in a wide signal width and little undershoot and overshoot. On the other hand, the waveforms at 0[mm] are signals in which half the length of the receiving transmission line functions as the coupled end and the other half functions as the isolated end. Therefore, the signal width is narrow and the instantaneous signal strength is large, but the signal component at the isolated end is also large, resulting in a signal with large undershoot and overshoot. In other words, depending on the settings of the comparator threshold, there is a possibility that the undershoot and overshoot parts of the composite signal FOUT2 may be erroneously detected as falling edges and rising edges. If erroneous detection occurs, an error occurs in the comparator output, resulting in a state in which the transmission signal cannot be demodulated normally.

[0098] As shown in Figure 14(a), in the first combination example of the conventional board structure, the difference between the magnitude of the composite signal FOUT2 at the position of -30 [mm] and the magnitude of the undershoot and overshoot of the composite signal FOUT2 at the position of 0 [mm] is approximately 21 [mV]. Hereinafter, this difference will be referred to as the "peak voltage difference." Note that the peak voltage difference is related to the settable range of the comparator threshold, and the larger this value is, the wider the settable range becomes.

[0099] In contrast, in the second and third combination examples of the substrate structure in which the ground of either the transmission transmission path or the reception transmission path is separated from the substrate, the peak voltage difference is improved to about 47 [mV] and about 39 [mV], respectively, as shown in Fig. 14 (b) and (c). In this case, if the composite signal FOUT2 is input to the comparator, the settable range of the threshold voltage at which the comparator signal switches is expanded, making it difficult for errors to occur in the output of the comparator. Also, in the fourth combination example of the substrate structure in which the grounds of both the transmission transmission path and the reception transmission path are separated from the substrate, as shown in Fig. 14 (d), the peak voltage difference is about 88.6 [mV]. This further expands the settable range of the input threshold of the comparator, making it possible to reduce errors.

[0100] In the example shown in Fig. 12(a) to (d), when forming the grounds 71c and 72c, and 81c, the thicknesses of the transmitting substrates 71a and 72a, and the receiving substrate 81a are set to about half the thickness of the conventional substrate in Fig. 12(a). This configuration is not limited, and they may be set to a different thickness, for example, to the same thickness as the conventional substrate. Also, the thicknesses of both ends of the grounds 71c and 72c, and 81c in the width direction may be set to a different thickness.

[0101] As described above, the wireless communication system 6 of the fourth embodiment is configured such that at least one of the transmission transmission path and the reception transmission path has at least a part of the ground serving as the reference potential formed at a position spaced apart from the substrate constituting each transmission path. Specifically, at least a part (surface portion) of the ground is located at a position facing the surface opposite to the surface on which the line pattern of the substrate constituting each transmission path is formed and spaced apart from the opposite surface. In addition, the spaces 71d, 72d, and 82d surrounded by the opposite surface of the substrate and the surface and both end portions of the ground are filled with a material (e.g., air) having a relative dielectric constant lower than that of the substrate.

[0102] With this configuration, the level difference between the output signals of the output ends that function as the coupled end and isolated end of the receiving transmission path can be made larger compared to the conventional configuration in which a ground that serves as a reference potential for both the transmitting transmission path and the receiving transmission path is formed on the substrate surface.

[0103] This makes it possible to increase the difference (peak voltage difference) between the magnitude of the undershoot and overshoot when the receiving transmission line is exactly halfway between the two transmitting transmission lines, and the magnitude of the composite signal FOUT2 when the receiving transmission line is located on one of the transmission lines. As a result, the setting range of the threshold voltage at which the comparator signal switches can be widened, making it difficult for comparator output errors to occur. (Fifth embodiment) Next, a fifth embodiment of the present invention will be described below. Figures 15 to 18 are diagrams showing the fifth embodiment. The fifth embodiment differs from the fourth embodiment in that the two transmission transmission paths and the reception transmission path are configured from differential lines. Fig. 15(a) is a perspective view showing the substrate structures of the transmission transmission paths 71A and 72A and the reception transmission path 21 of the wireless communication system 7 according to the fifth embodiment. Fig. 15(b) is a perspective view for explaining the substrate structures of the transmission transmission path 71A and the reception transmission path 21.

[0104] Fig. 16(a) is a diagram showing a fifth combination example of the substrate structure of the transmission transmission line and the reception transmission line, Fig. 16(b) is a cross-sectional view of line BB in Fig. 15(a) and shows a sixth combination example of the substrate structure of the transmission transmission line and the reception transmission line, Fig. 16(c) is a diagram showing a seventh combination example of the substrate structure of the transmission transmission line and the reception transmission line, and Fig. 16(d) is a diagram showing an eighth combination example of the substrate structure of the transmission transmission line and the reception transmission line. As shown in FIGS. 15(a) and 15(b), the wireless communication system 7 includes a transmitting device 10D and a receiving device 20. The transmitting device 10D has a configuration including transmission transmission paths 71A and 72A instead of the transmission transmission paths 11 and 12 in the transmitting device 10 of the first embodiment.

[0105] The transmission transmission lines 71A and 72A are obtained by changing the structure of the grounds 71c and 72c in the transmission transmission lines 71 and 72 of the fourth embodiment to a differential line pattern structure instead of the line patterns 71b and 72b. That is, the transmission transmission lines 71A and 72A are configured to include differential line patterns 71b' and 72b' instead of the single-ended line patterns 71b and 72b.

[0106] Figures 17(a), (b), (c), and (d) are diagrams showing frequency characteristics for a 2 [Gbps] transmission signal (input signal to the power feed point) in each of the combination examples in Figures 16(a) to (d). In Figures 17(a) to (d), the horizontal axis is frequency, the vertical axis is signal level [dB], the solid line is the signal level of the signal output from the coupled end with the transmission signal as a reference, and the dashed line waveform is the signal level of the signal output from the isolated end with the transmission signal as a reference.

[0107] Here, the combination example in Fig. 16(a) is a fifth combination example for comparison with the sixth to eighth combination examples according to the fifth embodiment. Specifically, this is a combination example of a substrate structure in which the transmission transmission lines 11 and 12 and the reception transmission line 21 are each configured with a conventional microstrip line. That is, the transmission transmission lines 11 and 12 and the reception transmission line 21 are configured such that their respective grounds are provided on the substrate surface without being spaced apart from the substrate. The combination example of Figure 16(b) is a sixth combination example of the substrate structures shown in Figures 15(a) and (b), and is a combination example in which the substrate structure of the receiving transmission path 21 is combined with the substrate structures of the transmitting transmission paths 71A and 72A relating to the fifth embodiment. In addition, the combination example of Figure 16 (c) is a seventh combination example in which the substrate structure of the receiving transmission path 81A, in which the ground structure of the receiving transmission path 21 is changed to the same structure as the ground structure of the receiving transmission path 81, is combined with the substrate structures of the transmitting transmission paths 11 and 12. Here, the receiving transmission line 81A is configured such that, in place of the single-ended line pattern 81b in the receiving transmission line 81, a differential line pattern 81b' which is a line pattern of a differential line. The combination example of FIG. 16(d) is an eighth combination example in which the substrate structures of the transmitting transmission paths 71A and 72A and the substrate structure of the receiving transmission path 81A are combined. Hereinafter, the frequency characteristics of the signals output from the two output terminals of the receiving transmission line at a maximum frequency of 1 [GHz] of the fundamental frequency of 2 [Gbps] data will be described. That is, the signal characteristics of "m1" and "m2" in Fig. 17(a) to (d) will be described. First, the frequency characteristics when the combination of the substrate structures of the transmitting substrate and the receiving substrate is the configuration of the fifth combination example shown in FIG. 16(a) will be described. In this case, the level difference between the output signal of the output end functioning as a coupled end of the receiving transmission line 21 and the output signal of the output end functioning as an isolated end is about 5 dB, as shown in FIG. 17(a).

[0108] Next, the level difference between the output signal at the coupled end and the output signal at the isolated end of the receiving transmission lines 21 and 81A is calculated when the combination of the substrate structures is the sixth and seventh combination examples shown in Figures 16(b) and 16(c). The level difference between the two combination examples in this case is about 7 to 8 dB, as shown in Figures 17(b) and 17(c). Furthermore, when the combination of substrate structures is the eighth combination example shown in FIG. 16(d), the level difference between the output signal at the coupled end of the receiving transmission path 81A and the output signal at the isolated end is approximately 11 dB, as shown in FIG. 17(d). That is, it can be seen that by using the ground 71c or 81c structure for either the substrate structure of the transmitting transmission path or the substrate structure of the receiving transmission path, the level difference is increased by about 2 to 3 dB compared to the level difference of the conventional structure. On the other hand, it can be seen that by using the ground 71c or 81c for both the substrate structures of the transmitting transmission path and the receiving transmission path, the level difference is increased by about 6 dB compared to the level difference in the conventional structure.

[0109] 18(a), (b), (c) and (d) are diagrams showing signal waveforms obtained by combining output signals from both ends of a receiving transmission line when a 2 Gbps signal is transmitted using the transmission lines of the respective combination examples shown in FIG. 16(a) to (d). More specifically, the diagrams show signal waveforms after filtering the ripple components of the combined signal.

[0110] 18(a)-(d), the horizontal axis is time, the vertical axis is voltage, and FOUT3 is the filtered composite signal when the moving position of the receiving transmission line is 0 [mm] and -40 [mm]. In FIG. 18(a)-(d), the solid line waveform shows the filtered composite signal FOUT3 when the moving position is -40 [mm], and the dashed line waveform shows the filtered composite signal FOUT3 when the moving position is 0 [mm].

[0111] In the filtered waveforms, the waveform at -40 [mm] (solid line) is the signal when the entire receiving transmission line is located on one of the two transmitting transmission lines, and the waveform at 0 [mm] (dashed line) is the signal when the receiving transmission line is located exactly in the middle of the two transmitting transmission lines (a position straddling two opposing power supply points or two termination points).

[0112] As shown in Figures 18(a) to (d), the -40[mm] waveforms are signals in which a normal coupled end signal is mixed with a small amount of the isolated end signal, resulting in a wide signal width with little undershoot or overshoot. On the other hand, the 0[mm] waveforms are signals in which half the length of the receiving transmission line functions as the coupled end, and the other half functions as the isolated end. As a result, the signal width is narrow and the instantaneous signal strength is large, but the isolated end signal is also large, resulting in a signal with large undershoot and overshoot. As shown in FIG. 18(a), in the fifth combination example of the conventional substrate structure, the peak voltage difference between the composite signal FOUT3 at the position of -40 [mm] and the undershoot and overshoot at the position of 0 [mm] is approximately 205 [mV].

[0113] In contrast, in the sixth and seventh combination examples of the board structure in which the ground of one of the transmission transmission path or the reception transmission path is separated from the board, the peak voltage difference is improved to about 265 [mV] and about 216 [mV], respectively, as shown in Figures 18(b) and (c). When this signal is input to the comparator 25, the settable range of the threshold voltage at which the signal of the comparator 25 switches is expanded, and errors in the output of the comparator 25 are less likely to occur. Also, in the eighth combination example of the board structure in which the grounds of both the transmission transmission path and the reception transmission path are separated from the board, as shown in Figure 18(d), the peak voltage difference is about 315 [mV]. This further expands the settable range of the input threshold of the comparator 25, making it possible to reduce errors.

[0114] As described above, the wireless communication system 7 of the fifth embodiment includes the transmission transmission lines 71A and 72A and the reception transmission line 81A, which are configured as differential lines. In addition, the grounds 71c, 72c, and 81c of the transmission transmission lines 71A and 72A and the reception transmission line 81A are formed at positions spaced apart from the substrate, similar to the fourth embodiment. With this configuration, the peak voltage difference can be made larger than in the fourth embodiment, and the threshold voltage range for switching the comparator signal can be made wider, making it more difficult for the comparator output error to occur.

[0115] (Sixth embodiment) Next, a sixth embodiment of the present invention will be described below. Figures 19 to 21 are diagrams showing the sixth embodiment. The sixth embodiment differs from the fifth embodiment in that a groove is formed between each pair of line patterns constituting a differential line on the surface on which the differential line patterns of each transmitting board and receiving board are formed.

[0116] FIG. 19 is a cross-sectional view showing an example of the substrate structure of the transmitting transmission lines 71B and 72B and the receiving transmission line 81B according to the sixth embodiment. As shown in FIG. 19, the transmitting transmission paths 71B and 72B have a configuration similar to that of the transmitting transmission paths 71A and 72A of the fifth embodiment described above, in which grooves 71e and 72e are formed on the surfaces of the transmitting substrates 71a and 72a on which the differential line patterns 71b' and 72b' are formed. Specifically, the grooves 71e and 72e are formed by excavating a portion of the substrate between a pair of line patterns constituting the differential lines on the formation surface of the differential line patterns 71b' and 72b' in a groove shape along the longitudinal direction of the line patterns. On the other hand, the receiving transmission line 81B has a configuration in which a groove 81e is formed on the surface of the receiving substrate 81a on which the differential line pattern 81b' is formed in the receiving transmission line 81A of the fifth embodiment.

[0117] Specifically, groove 81e, like grooves 71e and 72e, is formed by excavating a portion of the substrate between a pair of line patterns that constitute the differential lines on the formation surface of differential line pattern 81b' in a groove shape along the longitudinal direction of the line patterns. The grooves 71e and 72e are filled with a material having a lower dielectric constant than the transmitting substrates 71a and 72a. Similarly, the groove 81e is filled with a material having a lower dielectric constant than the receiving substrate 81a.

[0118] Specifically, the grooves 71e, 72e, and 81e can be filled with a material having a relative dielectric constant lower than that of the transmitting substrates 71a and 72a or the receiving substrate 81a, such as air, resin foam, PTFE, etc. In the sixth embodiment, the grooves 71e, 72d, and 81e are filled with air. In addition, grooves 71e, 72e, and 81e are not limited to being formed along the entire longitudinal length of the differential line pattern, but may be formed to a length shorter than the entire length, or may be formed with multiple grooves spaced apart at predetermined lengths, or may have other configurations.

[0119] Fig. 20 is a diagram showing frequency characteristics for a 2 [Gbps] transmission signal (input signal to the feeding point) in the board structure of Fig. 19. In Fig. 20, the horizontal axis is frequency, the vertical axis is signal level [dB], the solid line is the signal level of the signal output from the coupled end with the transmission signal as a reference, and the dashed line is the signal level of the signal output from the isolated end with the transmission signal as a reference.

[0120] Consider the frequency characteristics when the board structure shown in Fig. 19 is used. In this case, at a maximum frequency of 1 [GHz] of the fundamental frequency of 2 [Gbps] data, the level difference between the output signal at the coupled end and the output signal at the isolated end of the receiving transmission line 81B is about 12 [dB] as shown in Fig. 20. That is, it can be seen that by forming the grooves 71e, 72e, and 81e, the level difference is increased by about 1 [dB] compared to the substrate structure of the eighth combination example of the fifth embodiment.

[0121] Fig. 21 is a diagram showing a signal waveform after output signals from both ends of the receiving transmission line 81B are combined and the ripple component of this combined signal is filtered when a 2 [Gbps] signal is transmitted using the board structure shown in Fig. 19. In Fig. 21, the horizontal axis is time, the vertical axis is voltage, and FOUT3 is the combined signal after filtering when the moving position of the receiving transmission line is 0 [mm] and -40 [mm].

[0122] As shown in Fig. 21, the peak voltage difference between the signal magnitude at -40mm and the undershoot and overshoot magnitude at 0mm is approximately 323mV. In other words, compared to the peak voltage difference of 315mV in the eighth combination example of the fifth embodiment, the difference is about 8mV wider. This further widens the settable range of the comparator input threshold, making it possible to reduce errors in the comparator output.

[0123] As described above, the wireless communication system 7 of the sixth embodiment includes the transmission transmission paths 71B and 72B and the reception transmission path 81B. In addition, the grooves 71e and 72e are formed on the surfaces of the transmission boards 71a and 72a of the transmission transmission paths 71B and 72B on which the differential line patterns 71b' and 72b' are formed. Furthermore, the groove 81e is formed on the surface of the reception board 81a of the reception transmission path 81B on which the differential line pattern 81b' is formed.

[0124] With this configuration, the peak voltage difference can be made larger than in the eighth combination example of the fifth embodiment, and the setting range of the threshold voltage at which the comparator signal switches can be made wider, thereby making it more difficult for the comparator output error to occur. (Other embodiments)

[0125] The present invention can be embodied as, for example, a system, an apparatus, a method, a program, or a recording medium (storage medium), etc. Specifically, the present invention may be applied to a system composed of multiple devices (for example, a host computer, an interface device, a Web application, etc.), or may be applied to an apparatus composed of a single device.

[0126] The present invention can also be realized by supplying a program for realizing one or more of the functions of the above-described embodiments to a system or device via a network or a recording medium, and having one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more of the functions.

[0127] The disclosure of the above embodiment includes the following configurations and methods. (Configuration 1) At least two transmission transmission paths, at least one of a signal feed point and a signal termination point of which is disposed opposite to each other; A transmitting device including a transmitting means for inputting a signal to each of the power supply points of the at least two transmission transmission paths; a receiving transmission line that moves along the at least two transmitting transmission lines, electromagnetically couples with the transmitting transmission lines, and receives an excited signal; a receiving device including an output means for receiving signals from one end and the other end of the receiving transmission line, and outputting a signal to be demodulated based on the received signals; A wireless communication system comprising:

[0128] (Configuration 2) In configuration 1, The output means has a combining means for combining signals received from the one end and the other end of the receiving transmission path, and outputs the signal combined by the combining means as a signal to be subjected to the demodulation processing. (Configuration 3) In configuration 2, A wireless communication system, characterized in that impedance of a line from said output means to said one end and said other end of said receiving transmission line is configured to match a characteristic impedance of said receiving transmission line.

[0129] (Configuration 4) In configuration 1, The wireless communication system according to claim 1, wherein the output means outputs one of the signals received from the one end and the other end of the receiving transmission line as a signal to be subjected to the demodulation process. (Configuration 5) In configuration 4, A wireless communication system characterized in that the output means is connected to a demodulation circuit that performs the demodulation processing and to a termination resistor, and has a switching means that connects an end that outputs a signal having a larger signal width to the demodulation circuit and connects the other end to the termination resistor.

[0130] (Configuration 6) In any one of configurations 1 to 5, A wireless communication system, wherein the transmitting means inputs the same signal at the same timing to each of the power supply points of the at least two transmission transmission paths. (Configuration 7) In any one of configurations 1 to 6, A wireless communication system, wherein the output means has a suppression means for suppressing a signal component at an isolation end of a signal output from the reception transmission path.

[0131] (Configuration 8) In any one of configurations 1 to 6, A wireless communication system characterized in that the transmitting means has a signal generating means and a suppressing means for suppressing a ripple component contained in a signal output from the signal generating means at a stage upstream of the at least two transmission transmission paths. (Configuration 9) In any one of configurations 1 to 8, A wireless communication system, characterized in that at least one of the at least two transmitting transmission paths and the receiving transmission path has at least a portion of a ground that serves as a reference potential for the transmission path formed at a position separated from a substrate that constitutes the transmission path.

[0132] (Configuration 10) In configuration 9, A wireless communication system, comprising: at least a portion of the ground formed to face a surface of the substrate opposite to a surface on which a line pattern is formed. (Configuration 11) In configuration 10, A wireless communication system, comprising: a space between at least a portion of the ground and the opposite surface, the space being filled with a material having a dielectric constant lower than that of the substrate.

[0133] (Configuration 12) In any one of configurations 9 to 11, the at least two transmission transmission paths and the reception transmission path are each formed of a differential line; A wireless communication system, characterized in that at least one of the at least two transmitting transmission paths and the receiving transmission path has a groove formed in at least a portion of a portion between a pair of line patterns that constitute the differential line of a substrate that constitutes the transmission path. (Configuration 13) In configuration 12, 11. A wireless communication system according to claim 10, wherein the groove is filled with a material having a dielectric constant lower than that of the substrate.

[0134] (Configuration 14) A receiving device that receives signals from at least two transmission transmission paths in which at least one of a power supply point or a termination point of the signals is arranged opposite to each other, a receiving transmission line that moves along the at least two transmitting transmission lines, electromagnetically couples with the transmitting transmission lines, and receives an excited signal; an output means for receiving signals from one end and the other end of the reception transmission line, and outputting a signal to be demodulated based on the received signals, said receiving device comprising:

[0135] (Method 1) At least two transmission transmission paths, at least one of a signal feed point and a signal termination point of which is disposed opposite to each other; A transmitting device including a transmitting means for inputting a signal to the at least two transmission transmission paths; a receiving transmission line that moves along the at least two transmitting transmission lines, electromagnetically couples with the transmitting transmission lines, and receives an excited signal; and an output means for receiving a signal from the reception transmission path and outputting a signal to be demodulated based on the received signal, an input step in which the transmitting means inputs a signal to each of the power supply points of the at least two transmission transmission paths; The control method further comprises an output step in which the output means receives signals from one end and the other end of the reception transmission line, and outputs a signal to be subjected to demodulation processing based on the received signals.

[0136] (Method 2) a receiving transmission line that moves along at least two transmitting transmission lines, at least one of a feeding point or a termination point of a signal being arranged opposite to each other, and that electromagnetically couples with the transmitting transmission lines to receive an excited signal; and an output unit that receives a signal from the reception transmission line and outputs a signal to be demodulated based on the received signal, A control method comprising an output step in which the output means receives signals from one end and the other end of the reception transmission line, and outputs a signal to be demodulated based on the received signals.

[0137] (Configuration 15) A program for causing a computer to function as each of the means of the wireless communication system described in any one of configurations 1 to 13. (Configuration 16) A program for causing a computer to function as each of the means of the receiving device described in configuration 14. [Explanation of symbols]

[0138] 1 to 7... wireless communication system, 10A to 10D... transmitter, 11, 12, 41, 42, 71, 72... transmission transmission path, 13, 14, 43, 44... termination resistor, 15, 45... signal source, 16, 17... differential transmission buffer, 20, 50... receiver, 21, 51... reception transmission path, 22, 23, 52... combiner, 24... differential filter, 46, 47... transmission buffer, 54... filter, 25, 55... comparator, 62, 63... change-over switch

Claims

1. A transmission path comprising at least two transmission paths having a signal feed point at a first end and a signal termination point at a second end, A transmitting device comprising: transmitting means for inputting a signal to each of the power supply points of the at least two transmitting lines; A receiving transmission path that moves along at least two of the aforementioned transmitting transmission paths, is electromagnetically coupled with the transmitting transmission path, and receives the excited signal, A receiving device comprising: an output means that receives signals from one end and the other end of the receiving transmission line, respectively, and outputs a signal to be demodulated based on the received signals; Equipped with, A wireless communication system characterized in that the first end of one of the at least two transmission paths and the first end of the other transmission path are arranged facing each other along a predetermined direction.

2. A transmission path comprising at least two transmission paths having a signal feed point at a first end and a signal termination point at a second end, A transmitting device comprising: transmitting means for inputting a signal to each of the power supply points of the at least two transmitting lines; A receiving transmission path that moves along at least two of the aforementioned transmitting transmission paths, is electromagnetically coupled with the transmitting transmission path, and receives the excited signal, A receiving device comprising: an output means that receives signals from one end and the other end of the receiving transmission line, respectively, and outputs a signal to be demodulated based on the received signals; Equipped with, A wireless communication system characterized in that the second end of one of the at least two transmission paths and the second end of the other transmission path are arranged facing each other along a predetermined direction.

3. In the wireless communication system according to claim 1 or 2, The wireless communication system is characterized in that the output means includes a combining means for combining signals received from one end and the other end of the receiving transmission path, and outputs the signal combined by the combining means as the signal to be demodulated.

4. In the wireless communication system described in claim 3, A wireless communication system characterized in that the impedance of the line from the output means to one end and the other end of the receiving transmission line is configured to match the characteristic impedance of the receiving transmission line.

5. In the wireless communication system according to claim 1 or 2, The wireless communication system is characterized in that the output means outputs one of the signals received from the one end and the other end of the receiving transmission path as the signal to be demodulated.

6. In the wireless communication system according to claim 5, The output means is connected to a demodulation circuit and a termination resistor, respectively, which perform the demodulation processing, and is characterized by having a switching means that connects the end that outputs the signal with the larger signal width to the demodulation circuit and the other end to the termination resistor.

7. In the wireless communication system according to claim 1 or 2, The wireless communication system is characterized in that the transmitting means inputs the same signal to each of the power supply points of the at least two transmitting lines at the same time.

8. In the wireless communication system according to claim 1 or 2, The wireless communication system is characterized in that the output means has suppression means for suppressing the signal component at the isolation end of the signal output from the receiving transmission line.

9. In the wireless communication system according to claim 1 or 2, The wireless communication system is characterized in that the transmitting means comprises a signal generating means and a suppression means for suppressing ripple components included in the signal output from the signal generating means in front of at least two transmitting lines.

10. In the wireless communication system according to claim 1 or 2, A wireless communication system characterized in that at least one of the at least two transmitting transmission lines and the receiving transmission line has at least a portion of the ground that serves as the reference potential for the transmission line formed at a position spaced apart from the substrate constituting the transmission line.

11. In the wireless communication system according to claim 10, A wireless communication system characterized in that at least a portion of the ground is formed opposite to the surface of the substrate on which the line pattern is formed.

12. In the wireless communication system according to claim 11, A wireless communication system characterized in that the space between at least a portion of the ground and the opposite surface is filled with a material having a relative permittivity lower than that of the substrate.

13. In the wireless communication system according to claim 10, The at least two transmitting lines and the receiving line are each composed of differential lines. And so, The transmission path of at least one of the two transmission paths and the receiving transmission path This refers to the portion of the substrate constituting the transmission line between the pair of line patterns that constitute the differential line. A wireless communication system characterized by having grooves formed in at least a portion of it.

14. In the wireless communication system according to claim 13, The groove is characterized by being filled with a material having a relative permittivity lower than that of the substrate. A wireless communication system.

15. At least two having a signal feed point at a first end and a signal termination point at a second end. A receiving device that receives signals from a transmitting line, A receiving transmission path moves along at least two transmitting transmission paths, where the first end of one of the at least two transmitting transmission paths and the first end of the other of the at least two transmitting transmission paths are arranged facing each other in a predetermined direction, and electromagnetically couples with the transmitting transmission path to receive the excited signal. A receiving device characterized by comprising: an output means that receives signals from one end and the other end of the receiving transmission line, respectively, and outputs a signal to be demodulated based on the received signals.

16. A transmission path comprising at least two transmission paths having a signal feed point at a first end and a signal termination point at a second end, A transmitting device comprising: transmitting means for inputting signals to at least two transmission paths; A receiving transmission path that moves along at least two of the aforementioned transmitting transmission paths, is electromagnetically coupled with the transmitting transmission path, and receives the excited signal, The receiving device includes an output means that receives a signal from the receiving transmission line and outputs a signal to be demodulated based on the received signal, A control method for controlling a wireless communication system in which the first end of one of the at least two transmission paths and the first end of the other transmission path are arranged facing each other along a predetermined direction, The transmitting means includes an input step of inputting a signal to each of the power supply points of the at least two transmitting lines, A control method characterized in that the output means includes an output step of receiving signals from one end and the other end of the receiving transmission line, respectively, and outputting a signal to be demodulated based on the received signals.

17. A receiving transmission path is provided, wherein at least one of the feed point or termination point of a signal moves along at least two transmitting transmission paths arranged opposite each other, and is electromagnetically coupled with the transmitting transmission path to receive the excited signal. A control method for controlling a receiving device comprising an output means that receives a signal from the receiving transmission line and outputs a signal to be demodulated based on the received signal, A control method characterized in that the output means has an output step which receives signals from one end and the other end of the receiving transmission line, respectively, and outputs a signal to be demodulated based on the received signals.

18. A program for causing a computer to function as one of the means of a wireless communication system according to any one of claims 1 to 14.

19. A program for causing a computer to function as each of the means of the receiving device described in claim 15.

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