JP2015023076A - Shield structure of signal line and signal transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shield structure of a signal line in which shielding for reducing influence on external noise is properly performed while suppressing an increase in the number of electric wires.SOLUTION: A shield structure of a signal line includes: first signal lines 141, 142 which transmit a first signal; and second signal lines 144, 145 which transmit a second signal having a frequency different from that of the first signal, and in which, in the usage state, a first usage state is included where the signal is prevented from being transmitted simultaneously with the first signal lines 141, 142. The first signal lines 141, 142 serves as a shield line for shielding the second signal lines 144, 145.

Description

  The present invention relates to a signal line shield structure and a signal transmission method.

  2. Description of the Related Art Conventionally, in an electronic device, a plurality of circuit boards included therein are sometimes connected by cables (electric wires) for the purpose of signal transmission and the like. Such a cable may include a signal line that preferably reduces the influence of external noise (electromagnetic noise). Therefore, conventionally, a signal line for which the influence of external noise is to be reduced is shielded with a ground line. However, when the configuration in which the signal line is shielded by the ground line is employed, it is necessary to increase the number of the ground lines in accordance with the number of the signal lines. For example, the number of connector pins formed on the circuit board increases. Such problems arise.

  By the way, for example, Patent Document 1 and Patent Document 2 disclose a configuration in which a signal line is used as a shield. Patent Document 1 discloses that a low-speed signal line is used in order to prevent a harmonic component generated from a high-frequency signal from being transmitted to a shield ground line by electromagnetic coupling. Japanese Patent Application Laid-Open No. H11-260260 discloses that the read sense line and the write data line do not operate at the same time, and the other is used as a shield line in the read and write operations.

Japanese Patent No. 3564053 JP 2001-76490 A

  To reduce the influence of external noise, refer to the configurations of Patent Document 1 and Patent Document 2 and use a signal line as a shield line in place of the ground line instead of the signal line to reduce the influence of external noise. Can be considered. In this way, it is not necessary to increase the number of ground lines for shielding, and the above-described problem of an increase in connector pins can be avoided.

  However, when the signal line used as the shield line is in a normal use state where signal transmission is performed simultaneously with the signal line to be shielded, a sufficient shielding effect cannot be obtained, and the signal line to be shielded There is a concern that the signal quality in the system deteriorates (a concern when applying the configuration of Patent Document 1). Further, when the signal line used as the shield line and the signal line to be shielded are sometimes operated at the same time, the configuration of Patent Document 2 cannot be adopted.

  In view of the above points, an object of the present invention is to provide a signal line shield structure capable of appropriately performing a shield for reducing the influence of external noise while suppressing an increase in the number of electric wires. . Another object of the present invention is to provide a signal transmission method that easily exhibits a shielding effect in the shield structure of the signal line.

  To achieve the above object, the signal line shield structure of the present invention transmits a first signal line for transmitting a first signal and a second signal having a frequency different from that of the first signal, and uses the first signal line. And a second signal line including a first use state in which signal transmission is not performed simultaneously with the first signal line, and the first signal line includes the second signal. A configuration (first configuration) that is a shielded wire for shielding the wire is employed.

  According to this configuration, the usage state of the second signal line includes a usage state in which signal transmission is not performed simultaneously with the first signal line. For this reason, the first signal line can be used as a shield line for shielding the second signal line. In addition, since the use frequency is different between the first signal transmitted through the first signal line and the second signal transmitted through the second signal line, the two signal lines transmit signals simultaneously. Even if there is a usage state to be used, it is possible to suppress the effect of the first signal line as a shield line from being significantly impaired. That is, according to this configuration, it is possible to reduce the possibility that the second signal is affected by external noise without adding a ground line as a shield line. In this configuration, the first signal may be a low-frequency signal and the second signal may be a high-frequency signal.

  In the shield structure of the signal line of the first configuration, the use state of the second signal line includes a second use state in which signal transmission is performed simultaneously with the first signal line (first 2) may be employed. As described above, since the first signal transmitted through the first signal line and the second signal transmitted through the second signal line have different frequencies, the shield line of the first signal line is used. It is possible to prevent the effects of the Note that it is preferable that the first signal and the second signal are designed so that the difference in operating frequency is as large as possible.

  In the signal line shield structure of the second configuration, the second use state is preferably a temporary use state (third configuration). According to this configuration, the timing at which the second signal cannot be shielded is temporary, and a situation can be expected in which no substantial problem occurs even if the second signal is affected by external noise.

  In the signal line shield structure of any one of the first to third configurations, a filter circuit that suppresses transmission of a signal in a frequency band used for the second signal is provided with respect to the first signal line. The provided configuration (fourth configuration) is preferable. According to this configuration, it is possible to suppress a signal that affects the second signal line from flowing through the first signal line. Therefore, according to this configuration, not only when the second signal line does not transmit a signal simultaneously with the first signal line, but also when the second signal line transmits a signal simultaneously with the first signal line. Even when performing the above, it is easy to obtain a shielding effect by the first signal line.

  In the signal line shield structure of any one of the first to fourth configurations, the first signal line is arranged in parallel next to the second signal line, and the second signal line and the twisted pair Either a configuration forming a cable or a configuration forming a coaxial cable with the second signal line may be employed (fifth configuration). Among these, from the viewpoint of enhancing the shielding effect, it is preferable to use a twisted pair cable or a coaxial cable.

  In the signal line shield structure according to any one of the first to fifth configurations, the first signal line and the second signal line are connected to a first circuit board on which a tuner is mounted, and from the tuner. And a second circuit board provided with a circuit for processing an output signal, and the first signal line is a communication signal line used for communication, and the second signal The line may have a configuration (sixth configuration) that is an output signal line for transmitting a signal output from the tuner to the second circuit board. In this configuration, a usage state in which the second signal line does not transmit a signal simultaneously with the first signal line is a normal usage state (corresponding to viewing). In addition, the usage state in which the second signal line transmits a signal simultaneously with the first signal line is a temporary usage state (for example, corresponding to the time of channel selection). In particular, at the time of channel selection, the second signal is not substantially used, and there is no particular problem even if the second signal is not shielded. That is, it can be said that this configuration is a configuration to which the shield structure of the present invention can be easily applied.

  In order to achieve the above object, a signal transmission method of the present invention includes a first signal line and a second signal line through which a signal having a frequency different from that of the first signal line is transmitted, A signal transmission method applied to a shield structure of a signal line in which a first signal line is a shield line for shielding the second signal line, and the usage state of the second signal line is , Including a use state in which signal transmission is performed simultaneously with the first signal line and a use state in which signal transmission is not performed simultaneously with the first signal line, and is transmitted through the first signal line. It is preferable that the signal frequency be switched according to the usage state of the second signal line (seventh configuration). According to this configuration, for example, when the first signal and the second signal transmit signals simultaneously, it is possible to switch the use frequencies of the two signals as far as possible. For this reason, even when the first signal and the second signal transmit signals simultaneously, it is possible to suppress a significant reduction in the shielding effect by the first signal line. In addition, for example, in a use state where the first signal is transmitted through the first signal line and the second signal is not transmitted through the second signal line, the transmission speed of the first signal can be increased.

  In addition, in order to achieve the above object, the signal line shield structure of the present invention includes a first signal line for transmitting a first signal and a second signal having a frequency different from that of the first signal. And a filter circuit that is provided for the first signal line and suppresses transmission of a signal in a frequency band used for the second signal, the first signal line However, the configuration may be a shield line for shielding the second signal line. According to this configuration, even when the first signal and the second signal transmit signals simultaneously due to the presence of the filter circuit, the first signal line is used as a shield line for shielding the second signal line. Can be used. For this reason, according to this configuration, it is possible to reduce the possibility that the second signal is affected by external noise without adding a ground line as a shield line.

  According to the present invention, it is possible to provide a signal line shield structure capable of appropriately performing a shield for reducing the influence of external noise while suppressing an increase in the number of electric wires. Further, according to the present invention, it is possible to provide a signal transmission method that easily exhibits a shielding effect in the shield structure of the signal line.

The figure which showed typically the structure of the receiver to which the shield structure of the signal wire | line which concerns on embodiment of this invention is applied. Illustration for explaining the problems of the prior art The schematic diagram which shows the shield structure of the signal wire | line which concerns on embodiment of this invention The figure for demonstrating the relationship between IF signal and I2C signal in the receiver which concerns on embodiment of this invention. The figure for demonstrating the filter circuit provided in order to improve the shielding effect in the shield structure of the signal wire | line which concerns on embodiment of this invention. The schematic diagram which shows the modification of the shield structure of the signal wire | line which concerns on embodiment of this invention The schematic diagram which shows the other modification of the shield structure of the signal wire | line which concerns on embodiment of this invention The schematic sectional drawing of a coaxial cable in case a coaxial cable is adopted as the shield structure of the signal line concerning the embodiment of the present invention.

  Hereinafter, embodiments of a signal line shield structure and a signal transmission method according to the present invention will be described in detail with reference to the drawings. Hereinafter, a case where the present invention is applied to a receiving apparatus that receives a broadcast signal such as a digital television broadcast signal will be described as an example.

  FIG. 1 is a diagram schematically showing a configuration of a receiving apparatus 1 to which a signal line shield structure according to an embodiment of the present invention is applied. As shown in FIG. 1, a tuner substrate 11 and a signal processing substrate 12 are arranged inside the receiving device 1 in a separated state. A circuit pattern (not shown) is formed on each of the tuner board 11 and the signal processing board 12. Note that the tuner substrate 11 and the signal processing substrate 12 are separated from each other because, for example, the receiving device 1 has a structure that facilitates downsizing. The tuner board 11 is an example of the first circuit board of the present invention, and the signal processing board 12 is an example of the second circuit board of the present invention.

  The tuner board 11 is mounted with a tuner 13 for converting the radio wave of the channel selected by the user into an IF signal having an intermediate frequency. One end of the tuner board 11 and the signal processing board 12 is attached to a connector 11 a provided on the tuner board 11, and the other end is connected by a plurality of electric wires 14 attached to a connector 12 a provided on the signal processing board 12.

  The plurality of electric wires 14 include signal lines (IF1 signal line and IF2 signal line) for transmitting output signals (IF1 signal and IF2 signal in the present embodiment) output from the tuner 13. The signal processing board 12 is provided with a circuit for processing signals (IF1 signal and IF2 signal) output from the tuner 13. The IF1 signal and IF2 signal correspond to the second signal of the present invention. The IF1 signal line and the IF2 signal line correspond to the second signal line of the present invention.

  The signal processing board 12 is mounted with a control unit 15 (for example, configured with an IC chip). The control unit 15 is provided so as to be able to communicate with the tuner 13 through an I2C (Inter-Integrated Circuit). That is, the plurality of electric wires 14 include communication signal lines (I2C CLOCK signal line and I2C DATA signal line) for transmitting communication signals (I2C CLOCK and I2C DATA). Note that I2C CLOCK and I2C DATA correspond to the first signal of the present invention. The I2C CLOCK signal line and the I2C DATA signal line correspond to the first signal line of the present invention.

  In addition, the plurality of electric wires 14 include a ground line and an AGC signal line for transmitting a control (gain control of the tuner 13) signal (AGC (Automatic Gain Control) signal) to the tuner 13. It is. In other words, in the present embodiment, the plurality of electric wires 14 includes six electric wires.

  By the way, among the signals transmitted by the plurality of electric wires 14, the output signals (IF1 signal and IF2 signal) from the tuner 13 are preferably shielded in order to reduce the influence from external noise. In the conventional general technique, a ground line is used in such a case. Specifically, as illustrated in FIG. 2, a structure is adopted in which the IF1 signal line 141 is sandwiched between two ground lines 143a and 143b, and the IF2 signal line 142 is sandwiched between two ground lines 143b and 143c.

  However, when the structure as shown in FIG. 2 is adopted, the number of the plurality of electric wires 14 connecting the tuner board 11 and the signal processing board 12 increases due to the addition of the shield ground line (total of eight wires). Become). In this case, it is necessary to increase the number of pins of the connectors 11a and 12a (see FIG. 1). An increase in the number of pins of the connectors 11a and 12a may not be employed for reasons such as increasing the size of the receiving device 1, for example. In this regard, according to the shield structure of the signal line of the present embodiment, it is possible to suppress the situation where the output quality from the tuner 13 is affected by external noise and the reception quality is deteriorated while suppressing the increase in the number of electric wires. This will be described in detail below.

  FIG. 3 is a schematic diagram showing a signal line shield structure according to an embodiment of the present invention. As shown in FIG. 3, the IF1 signal line 141 (signal line to be shielded) is sandwiched between the ground line 143 and the I2C CLOCK signal line 144, and is arranged in parallel with these lines. Further, the IF2 signal line 142 (signal line to be shielded) is sandwiched between the I2C CLOCK signal line 144 and the I2C DATA signal line 145, and is arranged in parallel with these lines.

  Note that the six electric wires 141 to 146 may have a structure using an insulator such as FFC (Flexible Flat Cable). Further, the six electric wires 141 to 146 may be separately covered with an insulator and have a separate structure.

  In the structure shown in FIG. 3, the IF signal lines 141 and 142 are shielded by the I2C signal lines 144 and 145, and the IF signal can be shielded from external noise and transmitted. The reason for this will be described below. Prior to that, the relationship between the IF signal and the I2C signal in the receiving apparatus 1 will be described with reference to FIG.

  4 is a state in which the broadcast signal of the channel selected by the user is being output from the tuner 13, and the user is not instructed to select a channel. This state is a normal use state which is the most common use state of the receiving device 1. For example, an operation key provided on the main body of the receiving device 1 or an operation key (not shown) of a remote controller is used as a command related to channel selection by the user.

  At the time of viewing, no command related to channel selection has been issued, and the I2C signal, which is a communication signal, is not used (indicated by x in FIG. 4). On the other hand, the IF signal that is an output signal from the tuner 13 is used so that the user can view the program (marked with a circle in FIG. 4). That is, during viewing, signal transmission is performed only through IF signal lines 141 and 142, and signal transmission is not performed simultaneously through IF signal lines 141 and 142 and I2C signal lines 144 and 145. . The usage state of the IF signal lines 141 and 142 during viewing corresponds to the first usage state of the present invention.

  In FIG. 4, at the time of channel selection, a command related to channel selection is issued by the user, and communication is performed between the tuner 13 and the control unit 15. That is, at the time of channel selection, signal transmission is performed on the I2C signal (I2C signal lines 144 and 145) (circles in FIG. 4). In this embodiment, the IF signal (IF signal lines 141 and 142) is also used at the time of channel selection. However, since the IF signal is switched by channel selection, and it can be said that the IF signal at the time of channel selection is not substantially used, the use of the IF signal in FIG. 4 is different from the use of the I2C signal. They are separated (not marked as ◯ but marked as △).

  In the receiving apparatus 1, the channel selection is in a temporary use state, and the IF signal lines 141 and 142 and the I2C signal lines 144 and 145 at the time of channel selection are simultaneously used (a state where signals are transmitted simultaneously). Is temporary. The usage state of the IF signal lines 141 and 142 at the time of channel selection corresponds to the second usage state of the present invention. However, as described above, since the IF signal is not substantially used at the time of channel selection, in some cases, the IF signal may not be output at the time of channel selection. In this case, the IF signal is not transmitted through the IF signal lines 141 and 142 during channel selection.

  The status mode in FIG. 4 is a mode that is temporarily used when the reception state of the channel selected by the user is poor. In this mode, the control unit 15 communicates with the tuner 13 for the purpose of confirming the reception level at the tuner 13 or the like. In this mode, for example, it is preferable that the user can adjust the reception level while watching the screen state. For this reason, in the status mode, the IF signal and the I2C signal are simultaneously used (circles in FIG. 4).

  In the receiving apparatus 1, the status mode is a temporary use state, and the IF signal lines 141 and 142 and the I2C signal lines 144 and 145 are simultaneously used in the status mode (a state in which signals are transmitted simultaneously). Is temporary. The usage state of the IF signal lines 141 and 142 in the status mode corresponds to the second usage state of the present invention. The status mode is a special mode, and in some cases, a configuration in which this mode is not provided may be employed.

  As described above, the I2C signal is not used during viewing. That is, during viewing, the potential of the I2C signal is stable at a constant voltage (power supply voltage). Therefore, during viewing, the I2C signal lines 144 and 145 can be used as shield lines for shielding the IF signal lines 141 and 142. In consideration of this point, as shown in FIG. 3, the I2C CLOCK signal line 144 and the I2C DATA signal line 145 are arranged in parallel next to the IF signal lines 141 and 142, respectively, and the IF signal is externally transmitted. It is structured to shield from noise.

  At the time of tuning, the I2C signal is used, but the IF signal is not substantially used as described above. For this reason, at the time of tuning, even if the I2C signal lines 144 and 145 do not exhibit the function as shield lines, no problem is substantially caused. This also makes it possible to actively use the I2C signal lines 144 and 145 as shield lines. It is preferable that the frequency of the I2C signal is set to a low frequency (for example, 400 kHz or less), the frequency of the IF signal is set to a high frequency (for example, 1 MHz or more), and the use frequency is separated as much as possible between the I2C signal and the IF signal. . With this configuration, even when the IF signal lines 141 and 142 and the I2C signal lines 144 and 145 are used at the same time, the possibility that the IF signal is affected by noise can be reduced.

  In the status mode, the I2C signal and the IF signal are used simultaneously. For this reason, the shielding effect with respect to the IF signal lines 141 and 142 in the I2C signal lines 144 and 145 is reduced. However, as described above, if the design is such that the use frequency is separated between the I2C signal and the IF signal, the possibility that the IF signal is affected by noise can be reduced. Furthermore, in the present embodiment, the following devices are made.

  FIG. 5 is a diagram for explaining the filter circuit 30 provided to enhance the shielding effect in the signal line shield structure according to the embodiment of the present invention. As shown in FIG. 5, the filter circuit 30 is provided on the tuner substrate 11. More specifically, the filter circuit 30 is provided on a wiring that connects a connector pin (included in the connector 11a) for the I2C signal lines 144 and 145 and a tuner IC 13a (included in the tuner 13). .

  In this embodiment, there are two I2C signal lines, and the filter circuit 30 is provided corresponding to each of them (in this embodiment, two filter circuits 30 are provided). In FIG. 5, a resistor R is a pull-up resistor, which is provided to exhibit the function of I2C.

  The filter circuit 30 only needs to be capable of suppressing transmission of signals in a frequency band (for example, a frequency band of 1 MHz or higher) used for the IF signal through the I2C signal lines 144 and 145. In the present embodiment, the filter circuit 30 is designed such that the impedance to ground in the signal in the frequency band used for the IF signal is low. Specifically, the filter circuit 30 includes a capacitor C, one of which is connected to the I2C signal line 144 (or 145) and the other is connected to the ground. Note that the capacitance of the capacitor C is, for example, about 100 pF when the frequency band used for the IF signal is 1 MHz or more.

  In the present embodiment, the I2C signal lines 144 and 145 only need to be operated in a frequency band of 400 kHz or less. Therefore, even when the filter circuit 30 is provided, the I2C signal lines 144 and 145 can sufficiently function as communication signal lines. Since the signal of the frequency component (1 MHz or more) used in the IF signal is dropped to the ground due to the presence of the filter circuit 30, the I2C signal lines 144 and 145 are connected to the IF signal lines 141 and 142, respectively. Shield effect can be demonstrated. This shielding effect is also exhibited at the time of channel selection.

  The configuration of the filter circuit 30 is not limited to the above-described configuration, and various changes can be made. For example, a low-pass filter may be used. The filter circuit 30 may be provided not on the tuner substrate 11 side but on the signal processing substrate 12 side. In some cases, the filter circuit 30 may be provided on the tuner substrate 11 and the signal processing substrate 12. By adopting a design that reduces the communication speed of the I2C signal (lowers the frequency used) and keeps away from the frequency of the IF signal, the above-described filter circuit 30 can easily simplify its circuit configuration. .

  It is also effective to temporarily switch the frequency used for the I2C signal in the status mode. That is, a signal transmission method is adopted in which, for example, the frequency used for the I2C signal is 400 kHz (relatively high speed) except in the status mode, and the frequency used for the I2C signal is 100 kHz (relatively low speed) in the status mode. May be. It can be suppressed that the use frequency is further separated between the I2C signal and the IF signal, and the shielding effect by the I2C signal lines 144 and 145 is significantly reduced. The use frequency switching control may be performed by the control unit 15, for example.

  Note that the signal transmission method for switching the frequency used for the I2C signal according to the use state of the IF signal lines 144 and 145 may be applied during viewing depending on the case. Further, the frequency to be switched is not limited to two stages, and may be three or more stages.

  The embodiment described above is an exemplification of the present invention, and the scope of application of the present invention is not limited to the configuration of the embodiment described above. Of course, the above embodiments may be modified as appropriate without departing from the technical idea of the present invention.

  For example, in the embodiment described above, the I2C signal lines 144 and 145 used as shield lines are arranged in parallel next to the IF signal lines 141 and 142. For example, instead of this, as shown in FIG. 6, the IF1 signal line 141 and the I2C CLOCK signal line 144 form a twisted pair cable 16, and the IF2 signal line 142 and the I2C DATA signal line 145 are twisted pair cables. 17 may be formed. Each signal line 141, 142, 144, 145 is covered with an insulator. With this configuration, it is possible to expect an increase in the shielding effect in the I2C signal lines 144 and 145 as compared with the case where they are arranged in parallel.

  Further, the IF signal lines 141 and 142 and the I2C signal lines 144 and 145 do not constitute the twisted pair cables 16 and 17, but may form the coaxial cables 18 and 19 as shown in FIG. Good. In this case, as shown in FIG. 8, the IF1 signal line 141 (shielded side) is a core wire, and the I2C CLOCK signal line 144 (shielded side) is a conductor around the core wire. Is preferred. The coaxial cable 17 formed by combining the IF2 signal line 142 and the I2C DATA signal line 145 preferably has the same configuration. With this configuration, it is possible to expect an increase in the shielding effect in the I2C signal lines 144 and 145 as compared with the case where they are arranged in parallel.

  FIG. 8 is a schematic cross-sectional view of the coaxial cables 18 and 19 when the coaxial cables 18 and 19 are employed in the signal line shield structure according to the embodiment of the present invention. In FIG. 8, reference numerals 20 and 21 are both insulators.

  Further, as described above, the reception device 1 may not be provided with the status mode. In this case, the filter circuit 30 that suppresses transmission of signals in the frequency band used for the IF signal through the I2C signal lines 144 and 145 may be omitted.

  In the embodiment described above, it is assumed that the shielded signal line (I2C signal line) and the shielded signal line (IF signal line) are always used simultaneously. None (temporary simultaneous use is assumed). However, depending on the apparatus, there may be such a use state. Even in such a device, the signal line on the shield side and the signal line on the shield side are different in frequency, and the circuit that suppresses the transmission of signals in the frequency band used on the shield side is shielded. What is necessary is just to provide with respect to the signal line of the side. By adopting such a structure, the signal line can be shielded by another signal line.

  In the above description, the configuration in which the receiving device 1 includes one tuner 13 has been described. However, the present invention is naturally applicable even when the number of tuners 13 included in the receiving device 1 is two or more. In addition, the signal line shield structure and the signal transmission method of the present invention may be applied to apparatuses other than the receiving apparatus.

11 Tuner board (first circuit board)
12 Signal processing board (second circuit board)
13 Tuner 16, 17 Twisted pair cable 18, 19 Coaxial cable 30 Filter circuit 141 IF1 signal line (second signal line)
142 IF2 signal line (second signal line)
144 I2C CLOCK signal line (first signal line)
145 I2C DATA signal line (first signal line)

Claims (7)

A first signal line for transmitting a first signal;
A second signal that transmits a second signal having a frequency different from that of the first signal and includes a first usage state in which the signal is not transmitted simultaneously with the first signal line. Lines and,
With
The signal line shield structure, wherein the first signal line is a shield line for shielding the second signal line.   2. The signal line shield structure according to claim 1, wherein the use state of the second signal line includes a second use state in which a signal is transmitted simultaneously with the first signal line. .   3. The signal line shield structure according to claim 2, wherein the second use state is a temporary use state.   4. The filter circuit according to claim 1, wherein a filter circuit that suppresses transmission of a signal in a frequency band used for the second signal is provided for the first signal line. 5. Signal line shield structure.   The first signal line is arranged in parallel next to the second signal line, the second signal line forms a twisted pair cable, or the second signal line and the coaxial cable 5. The signal line shield structure according to claim 1, wherein the signal line shield structure is any one of the configurations forming the signal line. The first signal line and the second signal line include: a first circuit board on which a tuner is mounted; and a second circuit board on which a circuit for processing a signal output from the tuner is provided. Electric wire to be connected,
The first signal line is a communication signal line used for communication,
6. The signal according to claim 1, wherein the second signal line is an output signal line for transmitting a signal output from the tuner to the second circuit board. Wire shield structure. A first signal line; and a second signal line for transmitting a signal having a frequency different from that of the first signal line, wherein the first signal line shields the second signal line. A signal transmission method applied to a shield structure of a signal line, which is a shield line,
The usage state of the second signal line includes a usage state in which signal transmission is performed simultaneously with the first signal line and a usage state in which signal transmission is not performed simultaneously with the first signal line. ,
A signal transmission method characterized in that a frequency of a signal transmitted through the first signal line is switched depending on a use state of the second signal line.

Images