communication equipment

Abstract

To suppress noise in a system that performs wireless communication.SOLUTION: A communication device has a transmission line arranged on a substrate, a signal source connected to an input part of the transmission line, a metal member that functions as a ground in the transmission line and has a space between the metal member and the transmission line, and a termination circuit that terminates the transmission line. The termination circuit is arranged on a surface of the substrate where the metal member is arranged.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to wireless communication technology. [Background technology]

[0002] In recent years, an increasing number of production systems and robots are being equipped with devices for communicating data, and systems are being developed that perform high-speed data communication between mechanically operated moving parts and fixed parts. For example, Patent Document 1 discloses that data communication is performed between a rotating frame and a stationary frame by wirelessly coupling a transmission line in the rotating frame and a coupler in the stationary frame. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-224232 Summary of the Invention [Problem to be solved by the invention]

[0004] In a wireless communication system, one end of a transmission line is connected to a signal source, and the other end is terminated with a resistance substantially equal to the characteristic impedance of the transmission line. In this case, noise can be generated in the transmission line due to a disturbance in the characteristic impedance.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to suppress noise in a system that performs wireless communication. [Means for solving the problem]

[0006] In order to solve the above problem, a communication device according to the present invention comprises: Single-sided flexible On the board composition a transmission line connected to an input of the transmission line; , a circuit that transmits or receives differential signals and functions as a ground for the transmission line, Single-sided flexiblea metal member that is disposed with a portion spaced apart from the substrate; and a termination circuit that terminates the transmission line, Single-sided flexible On the board It The metal member is disposed on the surface. [Effects of the Invention]

[0007] According to the present invention, noise can be suppressed in a system that performs wireless communication. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a termination structure of a transmission line according to a first embodiment; [Figure 2] FIG. 10 is a diagram showing the reflection characteristics of the transmission line according to the first embodiment; [Figure 3] FIG. 1 is a diagram showing a circuit configuration at a terminal of a transmission line according to a first embodiment; [Figure 4] FIG. 10 is a diagram showing a termination structure of a transmission line according to a second embodiment; [Figure 5] FIG. 10 is a diagram showing a change in interference characteristics with respect to the distance between transmission lines according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Each embodiment will be described below with reference to the drawings. Note that the following embodiments do not necessarily limit the present invention. Furthermore, not all of the combinations of features described in each embodiment are necessarily essential to the solution of the present invention.

[0010] [First embodiment] FIG. 1 is a diagram illustrating a termination structure of a transmission line included in a communication device according to a first embodiment. First, a non-contact communication method and a termination method for a transmission line between a transmission line on a substrate having a space between it and a metal member serving as a ground and a transmission line on another substrate will be described with reference to FIG. 1(a) and FIG. 1(b). In FIGS. 1(a) and 1(b), differential transmission lines 102, which are two linear conductor members arranged side by side on a substrate 101, are transmission lines that transmit signals to a differential transmission line 202 on a substrate 201 via non-contact communication. The differential transmission lines 102 form a differential microstrip transmission line. The substrate 101 is a single-sided flexible substrate, and the copper foil on the substrate is arranged on the ground (metal) 103 side. Using a single-sided flexible substrate makes it possible to realize a low-cost termination structure for a transmission line while eliminating factors that cause impedance disturbance, such as vias. Flexible substrates are generally composed of an insulating base material such as polyimide, a coverlay, and copper foil. A signal output from a signal source 104 is input to the differential transmission line 102 as a differential signal via a differential transmission buffer 105 connected to one end (input section) of the differential transmission line 102.

[0011] The ground 103 is arranged so as to have a space between it and the differential transmission line 102, and serves as the reference potential for the differential transmission line 102 on the transmitting side. The width of the space between the ground 103 and the differential transmission line 102 is 9 mm, and the height of the space is 3 mm. The impedance of the transmission line changes depending on the size of this space and the configuration of the board. If the differential impedance of the differential transmission line 102 is Zdif, Zdif is derived by the following equation (1).

[0012]

number

[0013] The characteristic impedance Zo of each transmission line is calculated using the following equation (2).

[0014]

number

[0015] Here, e is Napier's constant, S is the distance between the transmission lines in the differential transmission line 102, h is the distance from the differential transmission line 102 to the ground 103, and ε r is the dielectric constant in the space from the differential transmission line 102 to the ground 103, L is the copper foil width of the transmission line, and t is the copper foil thickness of the transmission line. Here, the differential impedance Zdif is set to 100 Ω, S=0.5 mm, h=3 mm, ε r =1.0, L=3.3mm, t=0.035mm.

[0016] The differential transmission line 202 is a receiving-side transmission line that moves along the differential transmission line 102 and receives a signal from the transmitting-side differential transmission line 102 by non-contact communication. That is, a signal output from one end of the differential transmission line 102 is received by the differential transmission line 202 by non-contact communication, and after waveform shaping by the comparator 204, is detected as a received signal. The differential transmission line 102 performs non-contact communication by electromagnetic field coupling with the differential transmission line 202 that faces the surface of the substrate 101 opposite to the surface on which the ground 103 is arranged.

[0017] In this embodiment, each transmission line is a differential microstrip transmission line, but the configuration of the transmission line is not limited to this. For example, the transmission line on the receiving side may be an open-ended capacitive transmission line or a short-circuited inductive transmission line, or each transmission line may be a single-ended transmission line. In this embodiment, the differential transmission line 102 functions as a transmitting transmission line for transmitting signals, and the differential transmission line 202 functions as a receiving transmission line for receiving signals. However, the directional coupler formed by the transmitting transmission line and the receiving transmission line has reversibility. Therefore, by changing the circuit connected to the differential transmission line 102 and the circuit connected to the differential transmission line 202, the transmitting side and the receiving side can be swapped.

[0018] The termination resistor group 106 is arranged on the surface of the substrate 101 where the ground 103 is arranged. By arranging the termination resistor group 106 on the ground 103 side, the termination resistor group 106 and the substrate 201 do not come into contact with each other, and therefore, contactless communication can be achieved without any restrictions on the proximity distance between the substrates 101 in all areas in the direction of movement of the differential transmission line 202. Note that by removing the coverlay of the substrate 101 near the termination resistor group 106, the copper foil portion of the substrate 101 is exposed, allowing the termination resistor group 106 to be mounted. Here, the termination resistor group 106 consists of three resistors: a first resistor, a second resistor, and a third resistor, and terminates the differential transmission line 102. The first resistor connects one transmission line of the differential transmission line 102 to the conductive member 107, and the second resistor connects the other transmission line of the differential transmission line 102 to the conductive member 107. The third resistor is a resistor that connects the transmission lines of the differential transmission line 102 to each other.

[0019] The conductive member 107 is, for example, copper foil or solder formed on a substrate. The conductive member 107 is electrically connected to the ground 103 via a fixing member 108. The fixing member 108 is, for example, a fastener such as a conductive adhesive, a conductive tape, solder, or a screw. The fixing member 108 is provided to improve the electrical conductivity between one end of the resistor and the ground. For this reason, if the terminals of the termination resistor group 106 are directly connected to the ground 103 by soldering, for example, and electrical conductivity can be ensured, the fixing member 108 does not need to be provided. The electrical connection method is not limited to the above-described method, as long as the ground 103 acts as a reference potential for the differential transmission line 102.

[0020] 1(c), the ground 103 can be provided with a notch near the termination resistor group 106. By providing the notch, it is possible to prevent contact between the termination resistor group 106 and the ground 103 when the termination resistor group 106 is misaligned in mounting or when the substrate 101 is fixed in a laterally misaligned state. Preventing contact between the termination resistor group 106 and the ground 103 prevents the substrate 101 from floating above the ground 103, thereby stabilizing the impedance of the differential transmission line 102. This makes it possible to prevent deterioration of reflection characteristics due to geometric tolerances such as misalignment in mounting or misalignment when the substrate 101 is fixed.

[0021] It is desirable to set the constants of the termination resistor group 106 so that they match the differential impedance and common-mode impedance of the transmission line. If the differential impedance of the differential transmission line 102 is 100 Ω, the common-mode impedance will be approximately 60 Ω. In this case, it is desirable to set the third resistor connecting the transmission lines to approximately 180 Ω and the other resistors to approximately 120 Ω. Figure 2 shows the reflection characteristics of the differential transmission line 102 in this case, based on the differential transmit buffer 109 in a simulation. The horizontal axis represents frequency, and the vertical axis represents reflection characteristics based on the signal source 104. Figure 2 shows that reflection characteristics of -20 dB or less were obtained at each frequency. The length of the transmission line was 50 mm, and the characteristic impedance of the signal source 104 was matched to that of the transmission line.

[0022] Here, as shown in Figure 3(a), an example of a circuit having resistors between transmission lines and between a transmission line and ground has been described. However, the circuits may be configured with multiple resistors, or no resistors may be connected. For example, the termination circuits shown in Figures 3(b) and 3(c) may be used. These resistor circuits can be configured by the user according to the required cost, taking into account the signal bandwidth required for contactless communication and ease of assembly. By placing the termination resistor group 106 on the ground 103 side of the substrate 101, a termination structure that can suppress reflected noise in the transmission line can be realized with a simple structure.

[0023] A communication system including the communication device of this embodiment can be applied to, for example, an inkjet printer including a print head unit or a main body unit as a communication unit, or a robot that performs sliding movement.

[0024] [Second embodiment] In the first embodiment, a termination structure of a transmission line arranged on a linear substrate has been described. In the following, a termination structure of a transmission line provided in a communication device in a second embodiment will be described. The differences between the second embodiment and the first embodiment will be mainly described.

[0025] The termination structure of the transmission line in the second embodiment differs from that of the first embodiment in that the terminations face each other and signals output from two signal sources are input to the respective differential transmission lines. Note that the shape of the substrate may be a circular ring, a square ring, a pentagonal ring, or the like, as long as the terminations are annular and face each other.

[0026] FIG. 4 is a diagram showing a termination structure of a transmission line included in a communication device according to a second embodiment. The communication device according to this embodiment includes a substrate 301 having differential transmission lines 302, which are two parallel linear conductor members, and a substrate 401 having differential transmission lines 402. The substrates 301 and 401 form a transmitting-side differential transmission line that transmits signals through non-contact communication with the differential transmission line 502 on the substrate 501. The two substrates do not need to be separate substrates and may be integrated. The ground 303 included in the communication device according to this embodiment is disposed with a space between it and the differential transmission line, and serves as a reference potential for the differential transmission line. Here, the ground 303 has a rectangular ring shape, but it need not be ring-shaped as long as the distance to the plane that serves as the reference potential for the differential transmission line is approximately constant. Signals output from signal sources 304 and 404 are input as differential signals via differential transmission buffers 305 and 405 connected to one end of the differential transmission line. Although the case where there are two signal sources and two differential transmission lines will be described here, there may be more than two. Alternatively, there may be a single signal source, and signals may be input to each transmission line using a distributor or the like. The termination resistor group 306 and the termination resistor group 406 are arranged on the ground side of the board surface, and terminate each differential transmission line.

[0027] In this embodiment, the longitudinal length of the differential transmission lines of the communication device is set to 50 mm, and the distance g between the differential transmission lines at the termination is set to 1.5 mm. The vertical distance from the end of the differential transmission line of the communication device to the differential transmission line of the other communication device is set to 1.5 mm. The distance d from the termination to the circumferential direction of the board of the other communication device is set to 30 mm, the length of the differential transmission line of the other communication device is set to 3 mm, and the width of the differential transmission line of the other communication device is set to 1.6 mm.

[0028] Figure 5 shows the transmission characteristics of interference noise from a signal source at 5 GHz when d is set to 30 mm and the distance g between the differential transmission lines is changed. Figure 4 also shows the transmission characteristics from a signal source at 5 GHz when d is set to 0 mm and the distance g between the differential transmission lines is changed. As shown in Figure 4, the transmission characteristics of interference noise change with the distance g between the differential transmission lines, but the transmission characteristics are barely affected. In other words, by appropriately setting the distance g between the differential transmission lines, it is possible to reduce only the interference noise while maintaining the transmission characteristics. In this way, in a configuration in which a signal is branched in two or more directions and the terminations are facing each other, a termination structure that can suppress interference noise generated at each termination can be realized with a simple structure.

[0029] A communication system including the communication device of this embodiment can be applied to, for example, a network camera including a camera platform and an imaging unit as a communication unit, or a robot arm including a hand unit and an arm unit as a communication unit. [Explanation of symbols]

[0030] 101 Substrate 102 Differential transmission line 103 Grand 104 Signal source 106 Termination resistor group

Claims

1. A transmission line formed on a single-sided flexible substrate; a circuit connected to an input of the transmission line for transmitting or receiving a differential signal; a metal member that functions as a ground of the transmission line and is disposed with a portion spaced apart from the one-sided flexible substrate; a termination circuit that terminates the transmission line, The communication device is characterized in that the termination circuit is disposed on the surface of the single-sided flexible substrate on which the metal member is disposed.

2. A transmission line formed on a single-sided flexible substrate; a circuit connected to one end of the transmission line for transmitting or receiving a differential signal; a metal member that functions as a ground of the transmission line and is disposed with a portion spaced apart from the one-sided flexible substrate; a termination circuit disposed on the single-sided flexible substrate, the termination circuit terminating the transmission line; The communication device according to claim 1, wherein the metal member has a notch in the vicinity of where the termination circuit is disposed.

3. 3. The communication device according to claim 1, wherein the transmission line is a differential transmission line including two lines.

4. The communication device according to any one of claims 1 to 3, characterized in that the transmission line performs non-contact communication with another communication device that faces the surface of the one-sided flexible substrate opposite the surface on which the metal member is arranged by electromagnetic coupling.

5. The termination circuit comprises: In the case where the transmission line is a differential transmission line including two lines, a first resistor connected to one of the transmission lines and a conductor member formed on the one-sided flexible substrate; 4. The communication device according to claim 3, further comprising a second resistor connected to the other line of the transmission line and a conductor member formed on the one-sided flexible substrate.

6. The communication device according to claim 5 , wherein the conductor member connected to the metal member is electrically connected to the metal member by using a fixing member.

7. A communication device as described in Claim 6, characterized in that the fixing member includes a fixing device.

8. 7. The communication device according to claim 1, wherein a constant is set in the termination circuit so that a differential impedance and a common mode impedance of the transmission line match.

9. The termination circuit In the case where the transmission line is a differential transmission line including two lines, and a third resistor disposed between the differential transmission lines.

7. The communication device according to claim 5 or 6.

10. a first coupler disposed on a single-sided flexible substrate extending in a predetermined direction; a termination circuit that terminates the first coupler; a first circuit for transmitting or receiving a differential signal through the first coupler; a metal member that functions as a ground for the first coupler and is disposed with a portion spaced apart from the one-sided flexible substrate; a first communication unit having a second coupler that is electromagnetically coupled with the first coupler; a second communication unit having a second circuit that transmits or receives a differential signal via the second coupler; The wireless communication system according to claim 1, wherein the metal member has a notch in the vicinity of where the termination circuit is disposed.

Images