Patent Publication Number: US-2023163807-A1

Title: Wireless transmission system, control method, and storage medium

Description:
BACKGROUND 
     Field 
     The present disclosure relates to a wireless transmission system including a movable transmission path. 
     Description of the Related Art 
     A technique for controlling an apparatus that includes a rotatable movable portion, such as a robot hand portion or a network camera, through communication via a network or the like has been under development. The apparatus including such a rotatable movable portion can be configured to perform data communication through the rotatable movable portion in order to prevent issues such as a cable becoming entangled around a shaft while the rotatable movable portion is rotated. 
     Japanese Patent Application Laid-Open No. 4-45505 discusses a configuration in which an electric signal is input from one end of a ring-shaped first transmission path and the other end of the first transmission path is terminated, and a signal output from a second transmission path that is opposed to the first transmission path is detected. In this case, if the electric signal is input from a first end of the first transmission path and is transmitted to a second end of the first transmission path, a timing when the electric signal reaches the first end deviates from a timing when the electric signal reaches the second end. In other words, the electric signal reaches the second end with a delay with respect to the first end due to a transmission delay on the first transmission path. Accordingly, on the second transmission path, the signal reception timing varies depending on which part of the first transmission path the signal is received from. To address this, Japanese Patent Application Laid-Open No. 4-45505 discusses a technique for correcting a signal timing deviation depending on the position of the second transmission path using a variable delay unit that is connected to the second transmission path. Specifically, when the second transmission path is located near the first end of the first transmission path, the delay amount of the variable delay unit is increased, and when the second transmission path is located near the second end of the first transmission path, the delay amount of the variable delay unit is decreased. 
     However, according to the technique discussed in Japanese Patent Application Laid-Open No. 4-45505, as illustrated in  FIG.  6 A , a gap between a first end A for inputting a signal from a first transmission path  101  and a terminated second end B is small. Accordingly, a second transmission path  111  can be opposed to both the first end A and the second end B of the first transmission path  101 .  FIG.  6 B  illustrates an edge signal of an input signal detected by the second transmission path  111  (reception coupler). When the second transmission path  111  is moved above the first end A and the second end B of the first transmission path  101 , signals that are output from the first end A and the second end B of the first transmission path  101  at different timings are combined as illustrated in  FIG.  6 B . Accordingly, temporal “skipping” occurs in the signal output from the second transmission path, and if the temporal “skipping” exceeds a permissible jitter amount of a digital circuit, erroneous data may be output. 
     To address the above-described issue, Japanese Patent Application Laid-Open No. 2015-202415 discusses a method for establishing a stable communication while preventing data skipping by appropriately selecting and switching a plurality of sending-side transmission paths (send coupler) and receiving-side transmission paths (reception coupler). 
     However, in the method discussed in Japanese Patent Application Laid-Open No. 2015-202415, there is a need for routing an input channel signal to (N+1) transmission lines through a delay unit depending on a position of a rotatable movable portion relative to a fixed portion. Accordingly, a relative position detection unit and a switch unit for switching the input signal at a high speed are required, and thus the configuration thereof becomes complicated. 
     SUMMARY 
     In view of the above-described issues, various embodiments of the present disclosure are directed to preventing destabilization of communication with a simple configuration when signals are transmitted using a first transmission path coupler including a gap and a second transmission path coupler that is opposed to the first transmission path coupler in a non-contact state. 
     According to one embodiment of the present disclosure, a wireless transmission system includes a first transmission path coupler including transmission lines configured to transmit a signal, one end of each of the transmission lines being connected to a send unit, another end of each of the transmission lines being connected to a terminating resistor, the first transmission path coupler being annularly disposed, and a second transmission path coupler including transmission lines configured to transmit a signal, one end of each of the transmission lines being connected to a comparator, another end of each of the transmission lines being connected to a terminating resistor, the second transmission path coupler being configured to be moved across a gap of the first transmission path coupler. The second transmission path coupler generates a first signal at timings corresponding to a rising edge and a falling edge of an input signal input to the first transmission path coupler in a case where the input signal is transmitted to a position at which the first transmission path coupler and the second transmission path coupler perform an electric field and/or magnetic field coupling, a signal width of the first signal being substantially in proportion to a length of the electric field and/or magnetic field coupling of the first transmission path coupler and the second transmission path coupler. The signal width of the first signal is substantially equal to or greater than a difference in a transmission delay amount of the first transmission path coupler. 
     Further features of the present disclosure will become apparent from the following description of example embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a configuration example of a system according to a first example embodiment. 
         FIGS.  2 A and  2 B  are timing diagrams used to determine the size of a reception coupler according to the first example embodiment. 
         FIGS.  3 A and  3 B  are timing diagrams illustrating a case where the reception coupler according to the first example embodiment is moved along the circumference of a send coupler. 
         FIG.  4    illustrates a configuration example of a system according to a second example embodiment. 
         FIG.  5    illustrates a configuration example of another system according to the second example embodiment. 
         FIG.  6 A  is a configuration diagram for illustrating a system according to a related art, and  FIG.  6 B  is a timing diagram of the system according to the related art. 
         FIG.  7    is a system configuration diagram used to explain a principle common to the example embodiments. 
         FIG.  8    depicts four timing diagrams (A) through (D) that are used to explain a principle common to the example embodiments. 
         FIG.  9    is another system configuration diagram used to explain the principle common to the example embodiments. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It will be understood that components described in the following example embodiments are merely example features, and the present invention is not limited to the illustrated components. 
     Initially, a principle common to example embodiments of the present disclosure will be described.  FIG.  7    is a system configuration diagram for illustrating the principle common to the example embodiments. A transmission path coupler  101  includes a pair of signal lines and serves as a sending-side transmission path coupler for differential signals. The transmission path coupler  101  is hereinafter referred to as a send coupler  101 . Data transmitted from a signal source  103  (transmission unit) that is connected to the send coupler  101  is input to the send coupler  101  as differential signals through a differential send buffer  104  that is connected to the signal source  103  (hereinafter also referred to as a differential buffer  104 ). An end of the send coupler  101  that is opposite to the end connected to the signal source  103  is terminated by a terminating resistor  102  that is substantially equal to a transmission path characteristic impedance. 
     A transmission path coupler  111  includes a pair of signal lines and serves as a receiving-side transmission path coupler for differential signals. The transmission path coupler  111  is hereinafter referred to as the reception coupler  111 . The reception coupler  111  is movable along the send coupler  101 . The reception coupler  111  is coupled to the send coupler  101  by an effect of at least one of an electric field and a magnetic field. An input signal input from the signal source  103  is output from one end of the reception coupler  111  to a waveform shaping circuit  113  through an electric field and/or magnetic field coupling between the send coupler  101  and the reception coupler  111 . The waveform of the input signal is shaped by the waveform shaping circuit  113 , and the input signal is detected as a received signal. The other end of the reception coupler  111  is terminated by a terminating resistor  112  that is substantially equal to the transmission path characteristic impedance. 
     The send coupler  101  and the reception coupler  111  each operate as a directional coupler. An end of the reception coupler  111  that corresponds to the end of the send coupler  101  that is connected to the signal source  103  is referred to as a coupled end, and the other end of the reception coupler  111  is referred to as an isolation end. 
       FIG.  8    depicts four timing diagrams (A) though (D) illustrating a principle common to the example embodiments. Timing diagram (A) of  FIG.  8    illustrates a signal that is output from the signal source  103 , i.e., a signal that is input to the send coupler  101 . Timing diagram (B) of  FIG.  8    illustrates a signal that is output from the send coupler  101  at a position opposed to the reception coupler  111 . Timing diagram (C) of  FIG.  8    illustrates a signal that is output from the coupled end in a case where the isolation end of the reception coupler  111  is terminated and the signal is output from the coupled end. Timing diagram (D) of  FIG.  8    illustrates a signal that is output from the waveform shaping circuit  113 . 
     As illustrated in the timing diagrams (A)-(D) of  FIG.  8   , the signal transmitted through the send coupler  101  and the signal detected by the reception coupler  111  are differential signals. However, for simplicity of illustration, the differential signals are illustrated as single-ended signals corresponding to the differential signals. 
     The signal output from the signal source  103 , as illustrated in timing diagram (A) of  FIG.  8   , is input to the send coupler  101  through the differential buffer  104 . The signal transmitted on the send coupler  101  is transmitted at a transmission mode speed on a substrate, and is absorbed in the terminating resistor  102 , which is substantially equal to the characteristic impedance of the send coupler  101 . 
     Here, if the terminating resistor  102  completely matches the characteristic impedance of the send coupler  101 , the signal transmitted at a terminal end is not reflected and is absorbed in the terminating resistor  102 . 
     In such a case, the signal, on the send coupler  101 , at the position opposed to the reception coupler  111  becomes the signal as illustrated in timing diagram (B) of  FIG.  8   . The signal as illustrated in timing diagram (B) of  FIG.  8    lags behind the input signal by a period Δt 1 , which is the sum of a delay in the differential buffer  104  and a transmission delay. 
     The signal detected by the reception coupler  111 , as illustrated in timing diagram (C) of  FIG.  8   , rises in response to a rising edge of the signal illustrated in timing diagram (B) of  FIG.  8   , and then the rising edge of the signal illustrated in timing diagram (C) of  FIG.  8    is held for a period that is substantially in proportion to the length of the electric field and/or magnetic field coupling between the send coupler  101  and the reception coupler  111 . In other words, the rising edge of the signal illustrated in timing diagram (C) of  FIG.  8    is held for a period that is substantially in proportion to the length of the reception coupler  111 . In this case, the rising edge of the signal illustrated in timing diagram (C) of  FIG.  8    is held for a period ton which is substantially in proportion to a length L 1  of the reception coupler  111  illustrated in  FIG.  7   . After that, the signal illustrated in timing diagram (C) of  FIG.  8    becomes substantially “0”. 
     Further, the signal illustrated in timing diagram (C) of  FIG.  8    falls in response to a falling edge of the signal illustrated in timing diagram (B) of  FIG.  8   , and the falling edge of the signal illustrated in timing diagram (C) of  FIG.  8    is also held for the period ton. After that, the signal illustrated in timing diagram (C) of  FIG.  8    becomes substantially “0”. 
     The waveform shaping circuit  113  demodulates the input signal from the output signal from the reception coupler  111 . The waveform shaping circuit  113  is generally configured with a comparator provided with a hysteresis so that “1” is output when the signal illustrated in timing diagram (C) of  FIG.  8    (edge signal) detected by the reception coupler  111  is more than or equal to a positive threshold voltage Vth and “0” is output when the signal illustrated in timing diagram (C) of  FIG.  8    is less than or equal to a negative threshold voltage −Vth. The waveform shaping circuit  113  is hereinafter referred to as the comparator  113 . 
     In the signal illustrated in timing diagram (C) of  FIG.  8   , a reflected wave due to a small difference between the characteristic impedance of the send coupler  101  and the impedance of the terminating resistor  102 , a reflected wave due to a mismatch in the reception coupler  111 , and the like may occur as noise signals. However, if the noise signals are within the range of the above-described threshold voltages (Vth, −Vth), an output of the waveform shaping circuit  113  does not vary depending on the noise signal. The output of the waveform shaping circuit  113  varies depending only on the rising edge and falling edge of the signal illustrated in timing diagram (C) of  FIG.  8   . Thus, the terminating resistor  112  can demodulate the signal illustrated in timing diagram (D) of  FIG.  8    that has the same waveform as the waveform of the signal illustrated in timing diagram (B) of  FIG.  8   . 
     While  FIG.  7    illustrates an example where a long transmission path is used as the send coupler  101  and a short transmission path that is movable along the long transmission path is used as the reception coupler  111 , the present invention is not limited to this example. Since the directional coupler has reversibility, similar advantageous effects can be obtained even when the send coupler  101  and the reception coupler  111  are replaced as illustrated in  FIG.  9   . Each component included in a system configuration diagram illustrated in  FIG.  9    corresponds to the component denoted by the same reference numeral in the system configuration diagram illustrated in  FIG.  7   . 
     A first example embodiment of the present disclosure will be described next.  FIG.  1    illustrates a configuration example of a wireless transmission system according to the present example embodiment. In the wireless transmission system according to the present example embodiment, the send coupler  101  is annularly disposed on the circumference of a circle. The reception coupler  111  is configured to be moved on the circumference of the circle along the send coupler  101 . The reception coupler  111  outputs a signal from the coupled end. 
     In a case where the wireless transmission system according to the present example embodiment is disposed in an apparatus including a rotatable member, the send coupler  101  is disposed on the circumference of a circle about a rotational axis of the rotatable member. The reception coupler  111  is disposed such that the reception coupler  111  is opposed to the send coupler  101  and is movable on the circumference of the circle about the rotational axis of the rotatable member. The reception coupler  111  may be disposed on the outside or inside of the rotatable member. The send coupler  101  and the reception coupler  111  communicate signals through the electric field and/or magnetic field coupling. In  FIG.  1   , the illustration of members such as a substrate that supports the send coupler  101  and the reception coupler  111 , and ground conductors used when differential high-frequency transmission paths, such as microstrip lines or coplanar lines, are used as the send coupler  101  and the reception coupler  111  is omitted to simplify the description. 
       FIG.  1    illustrates a configuration example in which the transmission path coupler  101  functions as a send coupler and the transmission path coupler  111  functions as a reception coupler. However, the present invention is not limited to this example. The transmission path coupler  101  may function as a reception coupler and the transmission path coupler  111  may function as a send coupler. 
     The send coupler  101  and the reception coupler  111  may be included in the same apparatus, or may be included in different apparatuses. 
     In a case where an output signal obtained from the reception coupler  111  is smaller than a desired signal level, an amplifier may be disposed between the reception coupler  111  and the comparator  113 . 
     The send coupler  101  is a transmission path including a pair of conductors and is annularly disposed on the circumference of a circle. The send coupler  101  has a gap. One end of the send coupler  101  is connected to the signal source  103  through the differential buffer  104 . The other end of the send coupler  101  is connected to the terminating resistor  102 . A signal output from the signal source  103  is transmitted toward the terminating resistor  102  via the send coupler  101 , and flows into the terminating resistor  102 . 
     The reception coupler  111  is disposed such that the reception coupler  111  is opposed to the send coupler  101  on the circumference of the circle having the same center as that of the circumference on which the send coupler  101  is disposed. The reception coupler  111  is also a transmission path including a pair of conductors, and is formed with a length shorter than the send coupler  101 . The reception coupler  111  is disposed such that the reception coupler  111  can be coupled to the send coupler  101  through the electric field and/or magnetic field coupling, and is configured to generate a signal based on an electric signal flowing through the send coupler  101 . 
     The isolation end of the reception coupler  111  is terminated by the terminating resistor  112 . The coupled end of the reception coupler  111  is connected to the comparator  113 . The comparator  113  shapes the waveform of the signal received by the reception coupler  111 , and transmits the signal to a digital circuit  114  which is connected to the comparator  113 . 
     Here, the gap of the send coupler  101  is formed with a size that is smaller than the size of the reception coupler  111 . When the reception coupler  111  is opposed to the send coupler  101  with the gap interposed therebetween, the reception coupler  111  is electric-field and/or magnetic-field coupled to the both ends of the send coupler  101  at the same time. In this case, the reception coupler  111  receives both a signal with almost no delay from the input signal that is input to the send coupler  101 , and a signal that lags behind the input signal due to a transmission delay on the send coupler  101 . The reception coupler  111  receives a signal obtained by combining these two signals according to the ratio of coupling between the reception coupler  111  and the transmission paths at two ends of the send coupler  101 . 
       FIGS.  2 A and  2 B  are timing diagrams used to determine the size of the reception coupler  111 .  FIG.  2 A  illustrates a waveform of an input signal V(in) input to the send coupler  101 , a waveform of a signal V(term) output from the terminal end of the send coupler  101 , and a waveform of an output signal output from the coupled end of the reception coupler  111  for each angle of the arc of the reception coupler  111  in this order from top.  FIGS.  2 A and  2 B  illustrate the waveform of the output signal when the angle of the arc of the reception coupler  111  is 160 degrees, 170 degrees, 180 degrees, 190 degrees, and 200 degrees. When the angle of the arc of the reception coupler  111  is more than or equal to 180 degrees of the circumference of the circle, the signal width of the output signal from the reception coupler  111  is greater than a delay time of the signal V(term) with respect to the input signal of the send coupler  101 , so that the output signal from the reception coupler  111  has no discontinuity. 
     In the reception coupler  111  according to the present example embodiment, when the angle of the arc of the reception coupler  111  is 160 degrees or more and less than 180 degrees, the discontinuity of the received signal is 0.1 nanoseconds (ns) or less. Thus, since there are almost no comparators that can respond to such a small discontinuity, the output signal from the comparator  113  has no discontinuity. 
     Here, if a signal is transmitted at a speed of, for example, 1 Gbps, the maximum basic frequency of the signal is 500 MHz. On the other hand, if the received signal has a discontinuity of 0.1 ns, the basic frequency component of the signal is 5 GHz. In such a case, a low-pass filter (LPF) which passes the basic frequency of the signal and controls frequency components at the discontinuity is disposed between the reception coupler  111  and the comparator  113 , thus preventing the occurrence of a discontinuity in the output signal from the comparator  113  even when the discontinuity is present. To simplify the configuration, a capacitor of about a few pH may be disposed as the LPF in parallel between the outputs of differential transmission paths of the reception coupler  111  to filter the signal. In this case, the discontinuity of the signal is decreased, so that no discontinuity occurs in the output signal from the comparator  113  even when the angle of the arc is less than or equal to 180 degrees. Similarly, if the maximum frequency at which the comparator  113  can respond is higher than the maximum basic frequency of the signal and is lower than the frequency component at the discontinuity, no discontinuity occurs in the output signal from the comparator  113 . 
     The occurrence of a discontinuity in the signal can be prevented depending on the LPF disposed or the maximum response frequency of the comparator  113 . However, when the reception coupler  111  is moved above the gap of the send coupler  101 , a phase shift occurs in the received signal. This phase shift is to be prevented from exceeding a permissible jitter amount of the digital circuit  114  that is connected to the reception coupler  111 . 
       FIG.  2 B  is a timing diagram illustrating a case where the angle of the arc of the reception coupler  111  is 180 degrees of the circumference of the circle.  FIG.  2 B  illustrates an input signal (A) that is input to the send coupler  101 , a signal (B) that is output from the terminal end of the send coupler  101 , a signal (C) that is output from the reception coupler  111 , and a signal (D) that is output from the comparator  113  in this order from top. 
     As illustrated in  FIG.  2 B , the signal width ton of the signal (C) is substantially equal to a delay amount td of the signal (B) with respect to the signal (A). Accordingly, it can be seen that the signal (D) has no discontinuity. As seen from  FIG.  2 B , data skipping in the signal output from the comparator  113  is controlled by appropriately setting the size of the reception coupler  111 . 
       FIGS.  3 A and  3 B  are timing diagrams illustrating a case where the reception coupler  111  is moved along the circumference of the send coupler  101 .  FIG.  3 A  illustrates a case where the angle of the arc of the reception coupler  111  is 150 degrees, and  FIG.  3 B  illustrates a case where the angle of the arc of the reception coupler  111  is 180 degrees. 
       FIGS.  3 A and  3 B  each illustrate an input signal that is input to the send coupler  101 , a signal that is output from the terminal end of the send coupler  101 , and an output signal that is output from the reception coupler  111  at each relative angle between the send coupler  101  and the reception coupler  111  in this order from top. 
       FIG.  3 A  illustrates the waveform of the output signal from the reception coupler  111  when the relative angle is −160 degrees, −130 degrees, −100 degrees, −70 degrees, −40 degrees, −10 degrees, and 10 degrees. The reception coupler  111  mainly receives signals in the vicinity of the terminal end of the send coupler  101  when the relative angle between the reception coupler  111  and the send coupler  101  is −130 degrees. In this case, the threshold voltages Vth and −Vth of the comparator  113  are reached at timings corresponding to a rising edge and a falling edge that are affected by the delayed signal (signal at the terminal end) of the send coupler  101 . Accordingly, the output signal from the comparator  113  is output as the signal lagging behind the input signal that is input to the send coupler  101 . 
     The reception coupler  111  mainly receives signals in the vicinity of the end to which the signal from the send coupler  101  is input when the relative angle between the reception coupler  111  and the send coupler  101  is −100 degrees. In this case, the output signal from the comparator  113  is output with almost no effect of the signal (signal at the terminal end) with a delay due to a transmission delay on the send coupler  101 . Accordingly, in a case where the relative angle between the reception coupler  111  and the send coupler  101  is changed from −130 degrees to −100 degrees, the signal output from the comparator  113  is changed from the signal that is affected by the signal with a delay due to a transmission delay on the send coupler  101  to the signal that is not affected by the signal. In this case, skipping occurs at timings corresponding to a rising edge and a falling edge of the signal output from the comparator  113 . 
     In a case where the reception coupler  111  is reversely rotated with respect to the send coupler  101 , the angle of the reception coupler  111  relative to the send coupler  101  is changed from −100 degrees to −130 degrees. In this case, since the signal output from the comparator  113  is changed from the signal that is not affected by the signal with a delay due to a transmission delay on the send coupler  101  to the signal that is affected by the signal, skipping occurs at timings corresponding to a rising edge and a falling edge of the signal output from the comparator  113 . 
       FIG.  3 B  illustrates the waveform of the output signal from the reception coupler  111  when the relative angle is −190 degrees, −160 degrees, −130 degrees, −100 degrees, −70 degrees, −40 degrees, −10 degrees, and 10 degrees. As illustrated in  FIG.  3 B , the timings when the thresholds Vth and −Vth are exceeded in the case where the relative angle between the reception coupler  111  and the send coupler  101  is −130 degrees is substantially equal to that in the case where the relative angle is −100 degrees. Accordingly, even in a case where the relative angle between the reception coupler  111  and the send coupler  101  is changed from −130 degrees to −100 degrees, skipping does not occur at timings corresponding to a rising edge and a falling edge of the signal output from the comparator  113 . 
     As described above, the size of the reception coupler  111  is set to be substantially equal to the signal width of the signal output from the reception coupler  111  and the delay amount of the output signal at the terminal end with respect to the input signal to be input to the send coupler  101 , thus preventing skipping in the signal output from the comparator. Thus, data skipping on the receiving side can be prevented. 
     A second example embodiment of the present disclosure will be described below. While the first example embodiment uses the system configuration as illustrated in  FIG.  1   , the present invention is not limited to this configuration. The size of the reception coupler  111  can be determined in a similar manner in system configurations other than the above-described system configuration. 
       FIG.  4    illustrates a configuration example of a wireless transmission system different from the wireless transmission system according to the first example embodiment. In the configuration example illustrated in  FIG.  4   , the send coupler  101  is disposed on a side surface of a cylinder, and the reception coupler  111  is disposed on the outside of the cylinder such that the reception coupler  111  is opposed to the send coupler  101 . In this system configuration, the reception coupler  111  has such a size that the signal width of the output signal from the reception coupler  111  is substantially equal to the delay amount of the output signal at the terminal end with respect to the input signal to be input to the send coupler  101 , as in the first example embodiment. The configuration of the reception coupler  111  is not limited to this configuration. The reception coupler  111  may be configured as a coupler having a size large enough to hold a signal for a long period of time. In the system illustrated in  FIG.  4   , the send coupler  101  formed in a cylindrical shape includes differential transmission paths with the same length, and thus the differential transmission paths are more easily aligned in phase than in the system according to the first example embodiment, and the reflection at the terminal end can be reduced. 
       FIG.  5    illustrates a configuration example of another wireless transmission system different from the wireless transmission system according to the first example embodiment. 
     Unlike the system illustrated in  FIG.  4   , the system illustrated in  FIG.  5    has a configuration in which the reception coupler  111  is disposed on the inside of the send coupler  101 . As in the system illustrated in  FIG.  4   , the reception coupler  111  has such a size that the signal width of the output signal from the reception coupler  111  is substantially equal to the delay amount of the output signal at the terminal end with respect to the input signal to be input to the send coupler  101 . However, the configuration of the reception coupler  111  is not limited to this configuration. The reception coupler  111  may be configured as a coupler having a size large enough to hold a signal for a long period of time. 
     As described above, also in the system configuration illustrated in the second example embodiment, data skipping can be controlled by appropriately determining the size of the reception coupler  111 , as in the first example embodiment. 
     In a practical circuit, the digital circuit  114  includes a permissible jitter amount tj. Accordingly, the reception coupler  111  may be configured to have such a size that skipping within a range smaller than the permissible jitter amount tj can occur. Specifically, it is only required that the delay amount td of the output signal at the terminal end with respect to the input signal to be input to the send coupler  101  and the signal width ton of the output signal from the reception coupler  111  satisfy tj&lt;ton−td. 
     The wireless transmission systems according to the first and second example embodiments may be configured not only to communicate wireless signals, but also to transmit power. Instead of the transmission paths for sending and receiving differential signals according to the first and second example embodiments, a single transmission line may be used in other embodiments. 
     According to various embodiments of the present disclosure, it is possible to prevent destabilization of communication with a simple configuration when signals are transmitted using a first transmission path coupler including a gap and a second transmission path coupler that is opposed to the first transmission path coupler in a non-contact state. 
     Other Embodiments 
     Various embodiments of the present disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While example embodiments have been described, it is to be understood that the invention is not limited to the disclosed example embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2020-173313, filed Oct. 14, 2020, which is hereby incorporated by reference herein in its entirety.