Transmission system, transmission cable, transmission method, and display device

Abstract

To provide a transmission system, a transmission cable, a transmission method, and a display device, capable of stably performing signal transmission.SOLUTION: A transmission system comprises: a sending circuit including a non-contact coupling element having a first electrode to which a rectangular signal is input and a second electrode for outputting a differentiation signal of the rectangular signal; and a receiving circuit that receives the differentiation signal output from the sending circuit via a transmission line and compares the differentiation signal with a threshold to restore the rectangular signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a transmission system, a transmission cable, a transmission method, and a display device.

Background Art

[0002] In recent years, transmission systems using non-contact coupling such as inductive coupling or capacitive coupling have been proposed. The transmission system described in Patent Document 1 includes a transmission circuit that transmits a baseband rectangular signal using inductive coupling, and a reception circuit that restores the rectangular signal by comparing the transmitted rectangular signal with a threshold value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, non-contact coupling elements have frequency characteristics in which the attenuation amount of the DC component increases. For this reason, in the transmission system described in Patent Document 1, when rectangular signals of the same symbol are continuous, the level of the signal gradually decreases and may become lower than the threshold value. As a result, the signal cannot be correctly restored and stable signal transmission cannot be performed.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a transmission system, a transmission cable, a transmission method, and a display device capable of stable signal transmission.

Means for Solving the Problems

[0006] According to one aspect of the present invention, there is provided a transmission system comprising: a transmission circuit including a non-contact coupling element having a first electrode to which a rectangular signal is input and a second electrode that outputs a differential signal of the rectangular signal; and a reception circuit that receives the differential signal output from the transmission circuit via a transmission line and restores the rectangular signal by comparing the differential signal with a threshold value.

[0007] According to another aspect of the present invention, there is provided a transmission cable having a first connection portion and a second connection portion, wherein the first connection portion is connectable to a transmission circuit that outputs a differential signal corresponding to a rectangular signal, and the second connection portion includes a reception circuit that restores the differential signal to the rectangular signal.

[0008] According to another aspect of the present invention, there is provided a transmission method characterized by converting a rectangular signal into a differential signal using a non-contact coupling element having a first electrode and a second electrode, transmitting the differential signal to a reception circuit via a transmission line, and restoring the differential signal to the rectangular signal by the reception circuit.

[0009] A display device includes a display panel including a plurality of pixels, a transmission circuit, and a reception circuit. The transmission circuit includes a non-contact coupling element having a first electrode to which a rectangular signal is input and a second electrode that outputs a differential signal of the rectangular signal. The reception circuit receives the differential signal via a transmission line, restores the rectangular signal by comparing the differential signal with a threshold value, and the restored rectangular signal is input to the display panel.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a transmission system, a transmission cable, a transmission method, and a display device capable of stably transmitting signals.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals throughout the specification mean substantially the same components. The size and thickness of each configuration shown in the figures are shown for convenience of explanation, and the present invention is not necessarily limited to the size and thickness of the illustrated configuration.

[0013] [First Embodiment] FIG. 1 is a circuit block diagram of the transmission system in the present embodiment and a circuit block diagram of a system for transmitting and receiving signals with an electronic device. The electronic device may be, for example, a display device and may include a control device 1 and a display 3. The control device 1 and the display 3 are electrically connected to each other by a connection cable 2.

[0014] The control device 1 is a stationary device such as a STB (Set Top Box). The control device 1 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a signal processing circuit 11, a transmission circuit 12, etc. The CPU controls the overall operation of the control device 1 and the overall operation of the display 3 including the timing controller 32 according to a predefined application program. The ROM continues to hold the stored content even after the power is turned off, such as a non-volatile memory. The RAM is used as a work area for the operation of the CPU.

[0015] The signal processing circuit 11 receives a broadcast signal via radio waves, a cable, or the like. The signal processing circuit 11 converts a digital broadcast, a cable TV broadcast signal, etc. into a video signal and an audio signal by performing demodulation, error correction, and decoding processes. In the demodulation process, for example, OFDM (Orthogonal Frequency-Division Multiplexing) demodulation can be used. In the error correction, for example, Viterbi decoding can be used. In the decoding process, for example, RS (Reed Solomon) decoding can be used. The signal processing circuit 11 is further composed of a DSP (Digital Signal Porcessor), a frame memory, etc., and performs gamma correction, noise reduction processing, etc. on the video signal. The signal processing circuit 11 outputs the video signal and the audio signal to the transmission circuit 12 as serial differential signals. Here, the differential signal is a rectangular digital signal, and can be, for example, a serial LVDS (Low Voltage Differential Signaling) signal. The differential signal has two signals with different phases, and is a signal transmitted using two wirings in one lane. The differential signal changes with a predetermined potential difference centered on the common mode voltage. The common mode voltage can be, for example, 1.2V. The predetermined potential difference can be, for example, 350mV in the LVDS signal.

[0016] The transmission circuit 12 converts the rectangular digital signal input from the signal processing circuit 11 into a differential signal. The transmission circuit 12 transmits the differential signal to the display 3 via the connection cable 2. The connection cable 2 includes a conductor such as a tinned soft copper wire, an insulator that covers the periphery of the conductor, a shielding tape, a braided shield, a sheath, etc. The insulator can be, for example, polyethylene or the like. The shielding tape can be composed of, for example, aluminum, polyester, or the like. The braided shield can be, for example, a tinned soft copper wire or the like. The sheath can be, for example, polyvinyl chloride or the like. The connection cable 2 is provided with connection terminals at both ends. The connection cable 2 includes a plurality of differential signal lines 20. The differential signal line 20-1 transmits one signal of the differential signal to the display 3, and the differential signal line 20-2 transmits the other signal of the differential signal to the display 3. The number of differential signal lines 20 can increase or decrease according to the number of lanes.

[0017] The display 3 is a flat panel display device such as a liquid crystal display or an organic EL (Electroluminescence) display. The display 3 includes a receiving circuit 31, a timing controller 32, a data driver 33, data lines 34, a gate driver 35, gate lines 36, and a panel 37. The receiving circuit 31 receives the differential signal from the control device 1 via the connection cable 2. The receiving circuit 31 restores the differential signal to a rectangular digital signal and transmits it to the timing controller 32.

[0018] The timing controller 32 generates a timing signal for controlling the panel 37. The timing signal can control, for example, the timing for supplying pixel data to the data driver 33, the timing for supplying a shift clock to the gate driver 35, the timing for supplying an inversion pulse for each frame / line for preventing pixel degradation, etc.

[0019] Panel 37 includes a plurality of pixels arranged in a matrix. Each pixel includes a light-emitting element and a pixel circuit. When the display 3 is an organic EL display, the light-emitting element has a light-emitting layer of an organic material. The pixel circuit includes a switch transistor, a driving transistor, a capacitor, etc. The switch transistor and the driving transistor include a thin-film transistor, etc. In each light-emitting element, an RGB (R: Red, G: Green, B: Blue) color filter is provided. Instead of providing a color filter, a light-emitting element capable of emitting light of each color may be used.

[0020] The data driver 33 applies a data voltage corresponding to the luminance signal to the panel 37 via the data line 34. The gate driver 35 drives the gate of the switch transistor of the pixel circuit via the gate line 36. The gate driver 35 sequentially selects the gate line 36. The gate driver 35 applies a voltage that turns on the switch transistor connected to the selected gate line 36 to the gate line 36. The pixel circuit supplies a driving current corresponding to the data voltage to the light-emitting element and causes the light-emitting element to emit light.

[0021] Figure 2 is an example of a signal waveform in this embodiment. In Figure 2, the horizontal axis represents time and the vertical axis represents amplitude voltage. Figure 2(A) is the signal waveform of the differential signal in the transmission circuit 12. The differential signal is a digital signal and can be a rectangular signal or the like. At time t1, the voltage of the rectangular signal transitions from a low level to a high level. At time t2, the voltage of the rectangular signal transitions from a high level to a low level. At times t3 and t4, the voltage of the rectangular signal also transitions in the same manner.

[0022] FIG. 2(B) shows the signal waveform of the differential signal in the connection cable 2, which is the signal obtained by differentiating the rectangular signal in FIG. 2(A). At time t1, when the voltage of the rectangular signal transitions from the low level to the high level, the differential signal forms a pulse wave corresponding to the change amount of the voltage of the rectangular signal. At time t2, when the voltage of the rectangular signal transitions from the high level to the low level, the differential signal forms a pulse wave corresponding to the change amount of the voltage of the rectangular signal. Thus, the differential signal forms a pulse wave with a positive voltage in response to the rising edge of the rectangular signal, and forms a pulse wave with a negative voltage in response to the falling edge of the rectangular signal.

[0023] FIG. 2(C) shows the waveform of the output of the receiving circuit 31, which is the waveform of the signal obtained by restoring the differential waveform to a rectangular signal. In FIG. 2(B), when the voltage of the differential signal is equal to or higher than a predetermined threshold value th_H, the output signal of the receiving circuit 31 transitions to the high level. The receiving circuit 31 outputs a high-level voltage until it receives a differential signal with a voltage equal to or lower than the threshold value th_L. Also, in FIG. 2(B), when the voltage of the differential signal is equal to or lower than a predetermined threshold value th_L, the output signal of the receiving circuit 31 transitions to the low level. The receiving circuit 31 outputs a low-level voltage until it receives a differential signal with a voltage equal to or higher than the threshold value th_H.

[0024] At time t1, since the differential signal is a pulse wave with a positive voltage and is equal to or higher than the threshold value th_H, the receiving circuit 31 outputs a high-level voltage. From time t1 to t2, since the receiving circuit 31 does not receive a pulse wave with a negative voltage, the receiving circuit 31 continues to output a high-level voltage. At time t2, since the differential signal is a pulse wave with a negative voltage and is equal to or lower than the threshold value th_L, the receiving circuit 31 outputs a low-level voltage. From time t2 to t3, since the receiving circuit 31 does not receive a pulse wave with a positive voltage, the receiving circuit 31 continues to output a low-level voltage. Thus, the receiving circuit 31 detects the transition of the voltage of the rectangular signal from the low level to the high level or from the high level to the low level according to the differential signal. Based on the detected voltage transition, the receiving circuit 31 outputs a high-level voltage or a low-level voltage, and restores the rectangular signal from the differential signal.

[0025] Figure 3 is a circuit diagram of the transmission circuit in this embodiment. The signal processing circuit 11 outputs the rectangular signals P1 and N1 to the transmission circuit 12 via a plurality of lanes. The transmission circuit 12 includes a conversion IC 13, a drive circuit 14, a differential circuit 15, and a connection connector 16. The conversion IC 13 includes an operational amplifier 131, a deserialization circuit 132, a formatter 133, a serialization circuit 134, an operational amplifier 135, a controller 136, and a PLL (Phase Locked Loop) 137. The operational amplifier 131 connects the signal processing circuit 11 and the deserialization circuit 132. The operational amplifier 131 is provided for each lane of the rectangular signals P1 and N1 and outputs a differential signal of the rectangular signals P1 and N1. The deserialization circuit 132 converts a serial differential signal into a parallel signal. The parallel signal is input to the formatter 133.

[0026] The formatter 133 converts the signal transmission method into a different transmission method. For example, the formatter 133 converts an LVDS signal into a V-by-One (registered trademark) HS signal, an eDP (embedded DisplayPort) signal, or the like. The converted signal is input to the serialization circuit 134.

[0027] The serialization circuit 134 converts the parallel signal into a serial signal and outputs it to the operational amplifier 135. The operational amplifier 135 converts the serial signal into a serial differential signal. In this way, the conversion IC 13 converts a serial differential signal into a serial differential signal of a different transmission method.

[0028] The controller 136 receives from the signal processing circuit 11 settings such as the number of color depth bits of the display 3 and pre-emphasis settings. The number of color depth bits can be, for example, 6, 8, 10, 12 bits, etc. The pre-emphasis setting can be a parameter or the like for correcting the rise and fall slurs of the signal caused by the characteristics of the transmission line. Also, a control signal is input to the controller 136 via the connection connector 16 and the wiring 138-3. The control signal can be a signal indicating on or off of the power supply of the display 3, a signal indicating establishment of communication between the control device 1 and the display 3, etc. The PLL 137 is composed of a phase comparator, a loop filter, a voltage controlled oscillator, a frequency divider, etc., and synchronizes the phases of the output signals of the formatter 133 and the serializer 134. The conversion IC 13 outputs rectangular signals P2 and N2 to the drive circuit 14 via the wirings 138-1 and 138-2.

[0029] The drive circuit 14 includes operational amplifiers 141 and 142 and amplifies the rectangular signals P2 and N2 to a predetermined voltage. The drive circuit 14 is provided for each lane of the rectangular signals P2 and N2 of the conversion IC 13. The drive circuit 14 outputs the rectangular signal P3 to the differentiating circuit 15P via the wiring 143-1 and outputs the rectangular signal N3 to the differentiating circuit 15N via the wiring 143-2.

[0030] The differentiating circuits 15P and 15N are circuits that differentiate differential signals and are provided for the rectangular signals P3 and N3 for each lane. The differentiating circuit 15P differentiates the rectangular signal P3, and the differentiating circuit 15N differentiates the rectangular signal N3. The differential signal P4 is input to the connection connector 16 via the wiring 150-1, and the differential signal N4 is input to the connection connector 16 via the wiring 150-2.

[0031] The differential circuits 15P and 15N include termination resistors 151 and 153 and a capacitor 152. One electrode of the capacitor 152 is connected to the output node of the drive circuit 14, and the other electrode of the capacitor 152 is connected to the connection connector 16 via the wiring 150. The termination resistor 151 is connected to one electrode of the capacitor 152 and the ground wiring, and the termination resistor 153 is connected to one electrode of the capacitor 152 and the ground wiring. The connection connector 16 is connected to the connection cable 2.

[0032] Figure 4 is a circuit diagram of the receiving circuit in this embodiment. The receiving circuit 31 includes a connection connector 311 and a comparator 312, and restores the differential signals P4 and N4 transmitted from the transmitting circuit 12 to rectangular signals. The connection connector 311 includes an electrical terminal and a housing, and can be detachably connected to a connector provided at the end of the connection cable 2.

[0033] The comparator 312 is a hysteresis comparator having two threshold values th_H and th_L, and is electrically connected to the connection connector 311 via the wirings 317-1 and 317-2. The differential signals P4 and N4 are input to the comparator 312 via the wirings 317-1 and 317-2. In the comparator 312, when the voltage difference between the differential signals P4 and N4 exceeds the threshold values th_H and th_L, the comparator 312 performs a hysteresis operation according to the two threshold values th_H and th_L, and restores the differential signals P4 and N4 to rectangular signals P5 and N5. Hereinafter, the operation of the comparator 312 will be described with reference to FIG. 2.

[0034] At time t1 in FIG. 2, when the differential signal P4 becomes higher than the differential signal N4 by the threshold value th_H, the levels of the rectangular signals P5 and N5 are inverted. Even if the voltage difference between the differential signals P4 and N4 becomes smaller than the threshold value th_H at time t11, the state of the comparator 312 does not change. Therefore, the levels of the rectangular signals P5 and N5 do not change either. At time t2, when the voltage difference between the differential signals P4 and N4 becomes smaller than the threshold value th_L, the levels of the rectangular signals P5 and N5 are inverted.

[0035] As described above, the comparator 312 having hysteresis can restore the differential signals P4 and N4 to rectangular signals P5 and N5. The rectangular signals P5 and N5 are input to the timing controller 32 via the wirings 318-1 and 318-2. Further, a control signal is output from the timing controller 32 to the connection connector 311 via the wiring 318-3. The control signal includes, for example, a signal indicating on or off of the power supply of the display 3, and a signal indicating establishment of communication between the control device 1 and the display 3. Note that the reception circuit 31 may be provided in the timing controller 32.

[0036] FIG. 5 is a plan view of a circuit board of the control device in the present embodiment. FIG. 6 is a cross-sectional view of the circuit board of the control device in the present embodiment, and is a cross-sectional view of the circuit board taken along line VI-VI' in FIG. 5. In FIG. 5, two directions parallel and orthogonal to the main surface of the circuit board 4 are defined as the X direction and the Y direction, and the direction perpendicular to the main surface of the circuit board 4 is defined as the Z direction. The circuit board 4 can be a multilayer substrate including an insulating layer and a wiring layer. The insulating layer can be, for example, a PCB (Printed Circuit Board) and can be composed of paper phenol, glass epoxy, or the like. The wiring layer can be composed of copper, aluminum, or the like. The circuit board 4 includes via holes 154 and 157 on one main surface 41, and via holes 158 and 159 on the other main surface 42.

[0037] The signal processing circuit 11 and the conversion IC 13 are provided adjacent to each other on the main surface 41 of the circuit board 4. The signal processing circuit 11 is electrically connected to the conversion IC 13. The conversion IC 13 is electrically connected to the drive circuit 14 via the wirings 138-1 and 138-2. Further, the conversion IC 13 is electrically connected to the connection connector 16 via the wiring 138-3. The drive circuits 14 are arranged at a predetermined interval in the Y direction. The drive circuit 14 is electrically connected to the via hole 154 via the wirings 143-1 and 143-2. The via hole 154 is provided adjacent to the drive circuit 14 along the Y direction. The differential circuits 15P and 15N are preferably provided symmetrically, and the differential circuits 15P and 15N are symmetric with respect to the X direction in a plan view.

[0038] The capacitor 152 is composed of a first electrode 152A and a second electrode 152B. The electrodes 152A and 152B are made of the same material as the wirings 150-1 and 150-2. The material of the electrodes 152A and 152B can be, for example, copper, aluminum, etc. The electrodes 152A and 152B form a rectangle in a plan view. The shape of the electrodes 152A and 152B is not limited to a rectangle, and may be, for example, a trapezoid, a parallelogram, etc. The length of the electrodes 152A and 152B in the X direction can be, for example, 5 mm. The length of the electrodes 152A and 152B in the Y direction can be, for example, 1 mm. Also, the electrodes 152A and 152B can have the same thickness as the wiring layer in a cross-sectional view.

[0039] In a plan view, the electrodes 152A and 152B are provided so as to overlap. The electrodes 152A and 152B extend in the X direction and are arranged with a predetermined interval in the Y direction. The predetermined interval may be a length at which the electrodes 152A and 152B do not cause crosstalk with other adjacent electrodes 152A and 152B. The predetermined interval is preferably, for example, three times or more the length of the electrodes 152A and 152B in the Y direction. In a cross-sectional view, the electrodes 152A and 152B can be provided in different wiring layers. The electrodes 152A and 152B are non-contact and can be provided to face each other with an insulating layer therebetween. The interval between the electrodes 152A and 152B in a cross-sectional view is the same as the thickness of the insulating layer and can be, for example, 1 mm.

[0040] The wiring layer on the main surface 41 and the wiring layer provided with the electrode 152A are electrically connected in a vertical direction with respect to the main surface 41 through the via hole 154. One terminal of the electrode 152A in the X direction is electrically connected to the via hole 154. The other terminal of the electrode 152A in the X direction is electrically connected to the via hole 158. The wiring layer provided with the electrode 152A and the wiring layer on the main surface 42 are electrically connected in a vertical direction with respect to the main surface 42 through the via hole 158. The via hole 158 is electrically connected to the termination resistor 151 on the main surface 42.

[0041] The termination resistor 153 is electrically connected to the via hole 159 on the main surface 42. The wiring layer on the main surface 42 and the wiring layer provided with the electrode 152B are electrically connected in the vertical direction with respect to the main surface 42 via the via hole 159. One terminal of the electrode 152B in the X direction is electrically connected to the via hole 159. The other terminal of the electrode 152B in the X direction is electrically connected to the via hole 157. The wiring layer provided with the electrode 152B and the wiring layer on the main surface 41 are electrically connected in the vertical direction with respect to the main surface 41 via the via hole 157. The via hole 157 is electrically connected to the connection connector 16 via the wiring 150-1 on the main surface 41. The connection connector 16 is provided along the end of the circuit board 4 in the X direction. The connection connector 16 is electrically connected to the display 3 via the connection cable 2.

[0042] In the circuit board 4, the electrodes 152A and 152B face each other and are provided in two different wiring layers via an insulating layer. The electrodes 152A and 152B form the capacitor 152. A rectangular signal is input to the electrode 152A, and a differential signal is output from the electrode 152B. In this way, the capacitor 152 converts the rectangular signal into a differential signal.

[0043] As described above, according to this embodiment, in the transmission circuit, a rectangular signal is input to the first electrode, a differential signal is output from the second electrode, and is output to the receiving circuit. The receiving circuit can restore the differential signal to a rectangular signal by comparing the differential signal with a threshold value. Thereby, the transmission system can perform stable signal transmission.

[0044] [Second Embodiment] Subsequently, the transmission system in this embodiment will be described. The transmission system in this embodiment is different from the transmission system in the first embodiment in that a receiving circuit is provided at the connection terminal. Hereinafter, the description will focus on the configuration different from the first embodiment.

[0045] Figure 7 is a circuit diagram of the receiving circuit in this embodiment. The connection cable 2 includes a connection terminal 21, a cable 22, and a connection terminal 23. The connection terminal 21 is connected to the control device 1. The cable 22 includes differential signal lines 20-1 and 20-2, and transmits differential signals P4 and N4 to the receiving circuit 31. The connection terminal 23 includes the receiving circuit 31 and a terminal 231, and is connected to the display 3. The differential signals P4 and N4 are input to the receiving circuit 31 via the differential signal lines 20-1 and 20-2.

[0046] The receiving circuit 31 is provided inside the connection terminal 23. The receiving circuit 31 includes a comparator 312 and is electrically connected to the connection terminal 21 via the cable 22. Also, the receiving circuit 31 is electrically connected to the terminal 231 via wirings 318-1 and 318-2. The receiving circuit 31 uses the comparator 312 to restore the differential signals P4 and N4 to rectangular signals P5 and N5. The rectangular signals P5 and N5 are transmitted to the display 3 via the terminal 231. In this way, by providing the receiving circuit 31 in the connection terminal 23, the display 3 can receive the differential signals P4 and N4 transmitted from the control device 1 as rectangular signals P5 and N5 without modifying the circuit.

[0047] As described above, according to this embodiment, it is possible to apply the transmission system to an electronic device without modifying the receiving circuit of an existing electronic device or the like.

[0048] [Third Embodiment] Next, the transmission system in this embodiment will be described. The transmission system in this embodiment is different from the transmission system in the first embodiment in that the first electrode and the second electrode constituting the capacitor are provided in the same wiring layer. Hereinafter, the description will focus on the configuration different from the first embodiment.

[0049] Figures 8 and 9 are plan views of the circuit board of the control device in the present embodiment. In Fig. 8, the electrode 152A is formed in a substantially rectangular shape. One terminal of the electrode 152A is electrically connected to the drive circuit 14. The other terminal of the electrode 152A is electrically connected to the ground wiring via the termination resistor 151. The electrode 152B is formed in a substantially rectangular shape in the same manner as the electrode 152A, and is provided symmetrically with the electrode 152A in the X-Y plane. The shape of the electrodes 152A and 152B is not limited to a rectangle, and may be, for example, a trapezoid, a parallelogram, or the like. One terminal of the electrode 152B is electrically connected to the connection connector 16 via the wirings 150-1 and 150-2. The other terminal of the electrode 152B is electrically connected to the ground wiring via the termination resistor 153. The electrodes 152A and 152B are provided opposite to each other in the same wiring layer. As shown in Fig. 9, the electrodes 152A and 152B may be formed in a comb shape. When the electrodes 152A and 152B are formed in a comb shape, the electrodes 152A and 152B are provided symmetrically with each other in the X-Y plane, and the wiring pattern of the electrode 152A and the wiring pattern of the electrode 152B are provided so as to be alternately fitted. In this way, the electrodes 152A and 152B can form the capacitor 152 in the same wiring layer. Note that the electrodes 152A and 152B may be provided not only on the PCB but also on an FPC (Flexible Printed Circuits) or the like.

[0050] As described above, according to the present embodiment, the differentiating circuit can be surface-mounted on the circuit board, and the circuit board can be made thinner.

Description of Reference Numerals

[0051] 1: Control device 12: Transmission circuit 15: Differentiating circuit 151: Termination resistor 152: Capacitor 152A: First electrode 152B: Second electrode 2: Connection cable 3: Display 31: Receiving circuit 312: Comparator

Claims

1. A transmission circuit including a non-contact coupling element having a first electrode to which a rectangular signal is input and a second electrode that outputs a differential signal of the rectangular signal, a receiving circuit that receives the differential signal output from the transmission circuit via a transmission line and restores the rectangular signal by comparing the differential signal with a threshold value, wherein the transmission circuit is mounted on a substrate, wherein the first electrode and the second electrode are arranged inside the substrate so as to overlap in a plan view and are formed in two different wiring layers in a cross-sectional view, wherein a first terminal of the first electrode is electrically connected to a wiring layer on a first main surface of the substrate via a first via hole, and a second terminal of the first electrode is electrically connected to a first termination resistor on a second main surface of the substrate via a second via hole, wherein a first terminal of the second electrode is electrically connected to a wiring layer on a first main surface of the substrate via a third via hole, and a second terminal of the second electrode is electrically connected to a second termination resistor on a second main surface of the substrate via a fourth via hole. A transmission system characterized by this.

2. The transmission system according to claim 1, wherein the first electrode and the second electrode are a pair of wiring patterns facing each other on the substrate.

3. The transmission system according to claim 1, wherein each of the first electrode and the second electrode is connected to a ground wiring via a termination resistor.

4. wherein the differential signal forms a differential signal pair, The transmission system according to claim 1, wherein the coupling element includes a first coupling element corresponding to one differential signal of the differential signal pair and a second coupling element corresponding to the other differential signal of the differential signal pair.

5. The transmission system according to claim 4, wherein the first coupling element and the second coupling element are formed symmetrically.

6. The transmission system according to claim 4, wherein the receiving circuit includes a hysteresis comparator that compares the differential signal with a threshold value having hysteresis and restores the rectangular signal.

7. Further comprising a connection cable having a first connection portion and a second connection portion, The transmission system according to claim 1, wherein the first connection portion is connected to the transmission circuit, and the receiving circuit is arranged at the second connection portion.

8. The transmission system according to claim 1, further comprising a display panel connected to the receiving circuit. **Claim 9**: A transmission circuit including a non-contact coupling element having a first electrode to which a rectangular signal is input and a second electrode that outputs a differential signal of the rectangular signal, wherein the transmission circuit is mounted on a substrate, the first electrode and the second electrode are arranged inside the substrate so as to overlap in a plan view, and are formed in two different wiring layers in a cross-sectional view, a first terminal of the first electrode is electrically connected to a wiring layer on a first main surface of the substrate via a first via hole, and a second terminal of the first electrode is electrically connected to a first termination resistor on a second main surface of the substrate via a second via hole, a first terminal of the second electrode is electrically connected to a wiring layer on a first main surface of the substrate via a third via hole, and a second terminal of the second electrode is electrically connected to a second termination resistor on a second main surface of the substrate via a fourth via hole. The transmission circuit is characterized by this. **Claim 10** A display device comprising a display panel including a plurality of pixels, a transmission circuit, and a receiving circuit, wherein the transmission circuit includes a non-contact coupling element having a first electrode to which a rectangular signal is input and a second electrode that outputs a differential signal of the rectangular signal, the receiving circuit receives the differential signal via a transmission line, and restores the rectangular signal by comparing the differential signal with a threshold value, the restored rectangular signal is input to the display panel, the transmission circuit is mounted on a substrate, the first electrode and the second electrode are arranged inside the substrate so as to overlap in a plan view, and are formed in two different wiring layers in a cross-sectional view, a first terminal of the first electrode is electrically connected to a wiring layer on a first main surface of the substrate via a first via hole, and a second terminal of the first electrode is electrically connected to a first termination resistor on a second main surface of the substrate via a second via hole, a first terminal of the second electrode is electrically connected to a wiring layer on a first main surface of the substrate via a third via hole, and a second terminal of the second electrode is electrically connected to a second termination resistor on a second main surface of the substrate via a fourth via hole. The display device is characterized by this. **Claim 11** The display device according to claim 10, wherein the first electrode and the second electrode are a pair of wiring patterns facing each other on the substrate. **Claim 12**: A plurality of the first electrodes and a plurality of the second electrodes are respectively arranged, each of the plurality of the first electrodes and each of the plurality of the second electrodes extends in the X direction, the plurality of the first electrodes are arranged with intervals in the Y direction, and the plurality of the second electrodes are arranged with intervals in the Y direction, the transmission system according to claim 1, wherein the interval is not less than three times the length of each of the plurality of the first electrodes and the plurality of the second electrodes in the Y direction.

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