Signal processing device, signal processing board, and signal processing method

Abstract

In the present invention, a first communication unit and a second communication unit perform communication using a first signal and a second signal which are of different types. A first communication line connects the first communication unit and the second communication unit and transmits the first signal. A first branching line branches from a first branching point of the first communication line external to the second communication unit and connects to the second communication unit. The first branching line and the portion of the first communication line spanning from the first communication unit to the first branching point transmit the second signal. A first switching unit is disposed near the first branching point on the first branching line or at the first branching point, blocks propagation of the first signal to the first branching line when communication using the first signal is performed, and allows passage of the second signal to the first branching line when communication using the second signal is performed.

Description

Signal Processing Device, Signal Processing Substrate, and Signal Processing Method

[0001] The present disclosure relates to a signal processing device, a signal processing substrate, and a signal processing method.

[0002] A CIS (Complementary Metal Oxide Semiconductor Image Sensor) mounted on a camera often has, as a standard communication interface, two communication lines for image data communication and one communication line for control data communication. Image data communication is also called HS (High Speed) communication, and control data communication is also called BC (Back Channel) communication.

[0003] Depending on the application of the CIS, reduction of the interface area of the CIS and thinning of the cables used for the communication lines are required. Therefore, in order to reduce the interface area and the number of lines, a configuration may be used in which the communication lines for HS communication are also used for BC communication, that is, two different types of signals are transmitted using the same communication line.

[0004] In this case, since the communication partners are different for HS communication and BC communication, the two types of signals, the HS communication signal and the BC communication signal, are propagated to their respective communication partners after passing through one communication line. Therefore, a branch point where one communication line is divided into two communication lines and a branch line extending from the branch point in a direction different from the original communication line are provided.

[0005] As a signal transmission technique, a technique has been proposed in which the impedance of the main bus and the branch bus is matched to suppress reflected waves by adding or controlling a variable impedance element to change the resistance value of the branch bus. Also, in a configuration in which the driver's signal is shunted to the controller chip and the input / output interface at the branch point, a technique has been proposed to suppress signal reflection by arranging a termination resistor and a transistor in the controller chip.

[0006] Japanese Patent Application Laid-Open No. 10-126425, Japanese Patent Application Laid-Open No. 2000-174505

[0007] However, if the branching point is located outside the IC (Integrated Circuit), a communication line of a certain length is laid from the branching point to the BC communication transceiver terminals. During HS communication, the BC transceiver terminals become high impedance, creating an open stub on this communication line. The reflected waves from this open stub can cause degradation of the HS signal, potentially reducing communication performance.

[0008] Furthermore, the technique of matching impedance with a variable impedance element is a technique that reduces reflection noise due to differences in the path when the same signal is transmitted. Therefore, this technique is not effective in reducing signal degradation due to reflected waves when a single communication line is branched and two different signals are passed through each branch. Similarly, the technique of suppressing reflection by arranging termination resistors and transistors also applies to the same signal, and this technique is not effective in reducing signal degradation due to reflected waves when a single communication line is branched and two different signals are passed through each branch.

[0009] Therefore, this disclosure provides a signal processing device, a signal processing board, and a signal processing method that can improve communication performance when a single communication line is branched and two types of signals are passed through each branch.

[0010] According to this disclosure, the first communication unit and the second communication unit communicate using first and second signals of different types. The first communication line connects the first communication unit and the second communication unit and transmits the first signal. The first branch line branches off from the first communication line at a first branch point located outside the second communication unit and connects to the second communication unit, and transmits the second signal together with the portion of the first communication line from the first communication unit to the first branch point. The first switching unit is located near the first branch point on the first branch line or at the first branch point, and when communication using the first signal is performed, it blocks the propagation of the first signal to the first branch line, and when communication using the second signal is performed, it allows the second signal to pass through the first branch line.

[0011] This is a configuration diagram of the signal processing device according to the first embodiment. This is a block diagram of the AP. This is a diagram showing the signal flow in the signal processing device according to the first embodiment. This is a sequence diagram showing the state of each point when switching between HS communication and BC communication. This is a diagram showing the signal flow when no communication is performed. This is a diagram showing the signal flow when HS communication is performed. This is a diagram showing the signal flow of BC communication from AP to CIS. This is a diagram showing the signal flow of BC communication from CIS to AP. This is a flowchart of the switch switching process and the communication process. This is a diagram showing the signal flow in the signal processing device according to a modified example of the first embodiment. This is a diagram showing the signal flow in the signal processing device according to the second embodiment. This is a diagram showing the signal flow in the signal processing device according to a modified example of the second embodiment. This is a diagram showing the signal flow in the signal processing device according to the third embodiment. This is a diagram showing the signal flow in the signal processing device according to a modified example of the third embodiment. This is a diagram showing the signal flow in the signal processing device according to the fourth embodiment. This is a diagram for explaining the signal flow in the signal processing device according to the fourth embodiment. This is a diagram showing the signal flow in the signal processing device according to the fifth embodiment. This is a diagram for explaining the signal flow in the signal processing device according to a modified example of the fifth embodiment. This is a diagram showing an example of the schematic configuration of an endoscopic surgical system. This block diagram shows an example of the functional configuration of a camera head and CCU.

[0012] Preferred embodiments of this disclosure will be described in detail below with reference to the attached drawings. In this specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted. The description will be in the following order.

[0013] 1. First Embodiment 1.1. Overview of the signal processing device according to the first embodiment 1.2. Operation of the signal processing device 1.3. Signal flow in the signal processing device 1.4. Transition of connection state by HS communication and BC communication 1.5. Switching process and communication process 1.6. Effects 1.7. Modification of the first embodiment 1.8. Effects of the modification of the first embodiment 2. Second Embodiment 2.1. Signal processing device according to the second embodiment 2.2. Effects 2.3. Modification of the second embodiment 2.4. Effects of the modification of the second embodiment 3. Third Embodiment 3.1. Signal processing device according to the third embodiment 3.2. Effects 3.3. Modification of the third embodiment 3.4. Effects of the modification of the third embodiment 4. Fourth Embodiment 4.1. Signal processing device according to the fourth embodiment 4.2. Effects 5. Fifth Embodiment 5.1. Signal processing device according to the fifth embodiment 5.2. Effects 5.3. Modification of the Fifth Embodiment 5.4. Effects of the Modification of the Fifth Embodiment 6. Application Examples to Endoscopic Surgical Systems

[0014] <1. First Embodiment> HS communication signals and BC communication signals are signals with different frequency bandwidths and transmission speeds. Furthermore, HS communication signals and BC communication signals may also differ in modulation method and data format. HS communication is communication from the image sensor to the image processing unit. In contrast, BC communication is bidirectional communication between the image sensor and the image processing unit, and between the image processing unit and the image sensor. HS communication and BC communication can be transmitted and received without being constrained by each other's communication timing.

[0015] When transmitting and receiving two types of signals, HS communication signals and BC communication signals, simultaneously on a single communication line, there is a risk that the signals will interfere with each other, making accurate communication difficult. Therefore, when transmitting on a single communication line, HS communication and BC communication are performed alternately using a method called Time Division Duplex (TDD), which staggers the transmission and reception timing for each signal.

[0016] Furthermore, as mentioned above, since the two types of signals communicate with different partners, a branching point is provided to separate the communication lines. However, it has been common practice to place this branching point inside the IC of the image sensor or image processing unit. When the branching point is placed inside the IC, a new dedicated IC needs to be developed each time the signal specifications, such as transmission speed, differ. In this respect, since communication processing units tend to prioritize versatility, the hurdle of developing a new dedicated IC for each signal specification is high, and in some cases, it is difficult to obtain benefits such as cable miniaturization. In contrast, if the branching point is placed outside the IC, a general-purpose communication processing unit can be used regardless of the signal specifications, making it easier to realize a signal superposition system and reducing the development time and cost associated with developing new ICs.

[0017] However, if the branching point of the communication lines for HS communication and BC communication is simply placed outside the IC, the following problems arise. For example, when an HS communication signal reaches the branching point, it splits and propagates along the communication line to the HS communication receiver and the communication line to the BC communication transceiver.

[0018] Signals propagating along the BC communication line reach the input / output terminals of the BC communication transceiver after traveling along the communication line. During the HS communication period, the input / output terminals of the BC communication transceiver are in a high-impedance state. Then, an open stub is formed by the high impedance and the communication line after the branching. Therefore, signals propagating along the BC communication path undergo total reflection at the stub terminal and return to the branching point.

[0019] If the branching point is located outside the IC, the communication line after the branching point, which corresponds to the distance between the branching point and the signal reflection point, will have a certain distance. Therefore, the reflected signal will overlap with the original HS communication signal with a delay equal to the round-trip time of the communication line after the branching point, distorting the HS communication signal.

[0020] Here, because the intensity and timing of the reflected signal returning to the branching point change depending on the length of the communication line after branching, the degree of signal distortion depends on the board design, making it difficult to predict what kind of distortion will occur in the signal. In other words, reflected waves generated in the open stub communication line may cause unpredictable waveform degradation of the HS signal, potentially degrading signal quality. If signal quality deteriorates, it may become difficult to obtain the desired transmission rate and transmission distance, potentially leading to a decrease in communication performance.

[0021] Therefore, the technologies in each embodiment described below reduce signal degradation due to reflected waves when a single communication line is branched and two types of signals are passed through each, thereby improving the communication performance of the signal processing device.

[0022] <1.1. Overview of the signal processing device according to the first embodiment> Figure 1 is a configuration diagram of the signal processing device according to the first embodiment. As shown in Figure 1, the signal processing device 100 includes an AP (Application Processor) 1, a CIS 2, and a switch 3.

[0023] CIS2 converts the image obtained by the camera into an electrical signal and transmits it to AP1. CIS2 may be another image sensor, such as a CCD (Charge Coupled Device) image sensor.

[0024] AP1, for example, converts electrical signals sent from CIS2 to generate a visible photograph. In addition, AP1 may perform various information processing on image data to estimate, recognize, and distinguish subjects. Here, AP1 is an example of an image processing unit that performs image processing, and may be other image processing units such as FPGA (Field Programmable Gate Array).

[0025] AP1 and CIS2 are both integrated circuits (ICs). CIS2 and AP1 are connected by communication lines 41 and 42. Communication line 42 branches off at branching point 30 between CIS2 and AP1. From branching point 30, communication line 31 extends to AP1 via switch 3.

[0026] Here, CIS2 is an example of a "first communication unit," and AP1 is an example of a "second communication unit." Also, communication line 42 is an example of a "first communication line," and communication line 41 is an example of a "second communication line." In other words, CIS2, which is the first communication unit, and AP1, which is the second communication unit, are connected by the first communication line. Furthermore, CIS2, which is the first communication unit, and AP1, which is the second communication unit, are further connected by the second communication line in addition to the first communication line. Also, branching point 30 is an example of a "first branching point on the first communication line that exists outside the second communication unit," and communication line 31 extending from branching point 30 is an example of a "first branch line."

[0027] CIS2 includes an HS transmission driver 21, an inverted HS transmission driver 22, a BC reception driver 23, and a BC transmission driver 24. The output terminal of the HS transmission driver 21 is connected to the communication line 41. The output terminal of the inverted HS transmission driver 22 is connected to the communication line 42.

[0028] Furthermore, the CIS2 has a branching point 25 of the communication line 42 within the IC. The communication line 26 that branches off from the communication line 42 at the branching point 25 is connected to ground via a pull-down resistor 27. It is preferable to use a pull-down resistor 27 that is sufficiently higher than the termination resistor (for example, 1 MΩ). The communication line 26 also branches off between the branching point 25 and the pull-down resistor 27 and is connected to the input terminal of the BC receiving driver 23. Furthermore, the communication line 26 branches off again between the branching point 25 and the pull-down resistor 27 and is connected to the output terminal of the BC transmitting driver 24.

[0029] The HS transmission driver 21 receives the HS communication signal as input and amplifies the input signal. In this embodiment, the HS communication signal is a differential signal, and the signal amplified by the HS transmission driver 21 is the HS positive signal, which is the positive side of the differential signal. The HS transmission driver 21 outputs the HS positive signal to the communication line 41. The HS positive signal is transmitted to AP1 via the communication line 41.

[0030] The inverting HS transmission driver 22 receives the input signal for HS communication transmission, inverts the input signal, and amplifies the inverted signal. The signal amplified by the inverting HS transmission driver 22 is the HS negative signal, which is the negative side of the differential signal. The inverting HS transmission driver 22 outputs the HS negative signal to the communication line 42. The HS negative signal is transmitted to AP1 via the communication line 42.

[0031] An HS negative signal is an example of a "first signal." That is, the first signal is transmitted on the first communication line. Furthermore, both the HS negative signal and the HS positive signal are examples of "differential signals of the first signal." That is, the first communication unit CIS2 and the second communication unit AP1 transmit and receive differential signals of the first signal using both the first and second communication lines.

[0032] The BC receiving driver 23 receives the AP-side BC communication signal transmitted from AP1. The AP-side BC communication signal is sent via communication line 31, communication line 42, and communication line 26 branched off at branching point 25, with switch 3 in the closed state. The BC receiving driver 23 then amplifies the input AP-side BC communication signal and outputs it to a signal processing unit (not shown) in the subsequent stage.

[0033] The BC transmission driver 24 receives the CIS-side BC communication signal as input and amplifies the input CIS-side BC communication signal. The BC transmission driver 24 then outputs the amplified CIS-side BC communication signal to the communication line 26. The CIS-side BC communication signal is transmitted to AP1 via the communication line 26, the communication line 42, and the communication line 31 with switch 3 in a closed state.

[0034] The AP-side BC communication signal and the CIS-side BC communication signal are examples of the "second signal." That is, the second signal is transmitted via the first branch line along with the portion of the first communication line from the first communication section to the first branch point.

[0035] As mentioned above, the HS communication signal and the BC communication signal differ in frequency bandwidth and transmission speed. Furthermore, the HS communication signal and the BC communication signal may differ in modulation scheme and data format. In other words, the first communication unit, CIS2, and the second communication unit, AP1, communicate using different types of first and second signals. More specifically, the first communication unit, CIS2, and the second communication unit, AP1, communicate using first and second signals with different transmission speeds.

[0036] AP1 includes a differential amplifier 11, a switch control driver 12, a BC transmission driver 13, and a BC reception driver 14. The differential amplifier 11 has its positive input terminal connected to a communication line 41 and its negative input terminal connected to a communication line 42. The switch control driver 12 has its output terminal connected to a switch 3. The output terminal of the BC transmission driver 13 is connected to a communication line 31. The input terminal of the BC reception driver 14 is connected to a communication line 31.

[0037] The differential amplifier 11 receives the HS positive signal input via the communication line 41 at its positive input terminal. The differential amplifier 11 also receives the HS negative signal input via the communication line 41 at its negative input terminal. The differential amplifier 11 amplifies the difference between the HS positive signal and the HS negative signal and outputs it to a signal processing unit (not shown).

[0038] The switch control driver 12 is connected to the switch 3 via a dedicated line 5. The switch control driver 12 outputs a switch switching signal to switch the state of the switch 3 to open or closed.

[0039] The BC transmission driver 13 receives the AP-side BC communication signal as input and amplifies the AP-side BC communication signal. The BC transmission driver 13 then outputs the amplified AP-side BC communication signal to the communication line 31.

[0040] The BC receiving driver 14 receives the CIS-side BC communication signal from the communication line 31. The BC receiving driver 14 amplifies the input CIS-side BC communication signal. The BC receiving driver 14 then outputs the amplified CIS-side BC communication signal to a signal processing unit (not shown).

[0041] Switch 3 is a general-purpose switch. Switch 3 may be a contact-type switch or a non-contact-type switch. Switch 3 only needs to have a passband bandwidth for the frequency components of the signal to be passed through, and does not need to have the function of bandwidth-separating two types of signals. Also, since switch 3 generally has an input capacitance at its input terminal, even if the stub is disconnected, a large input capacitance can cause distortion of the HS communication signal waveform. Therefore, it is preferable that switch 3 has as small an input capacitance as possible. Note that the distortion of the HS negative signal may increase due to the input capacitance of switch 3, and it may no longer function as a differential signal with respect to the HS positive signal. In that case, it is preferable to install a dummy switch or a capacitance equivalent to the input capacitance of the switch on the communication line 41 side, so that the load on the HS positive signal is equivalent to that of the HS negative signal.

[0042] Switch 3 is located at or near the branching point 30. Switch 3 switches the connection and disconnection of the communication line 31 according to the switch switching signal from the switch control driver 12. The communication line 31 is connected to ground via a pull-down resistor 32. Switch 3 is an example of the "first switching unit". Switch 3 is located near or at the branching point 30, which is the first branching point on the communication line 31, which is the first branching line.

[0043] <1.2. Operation of the signal processing device> Figure 2 is a block diagram of AP. AP1 includes, for example, a receiver 101, a transceiver 102, a switching control unit 103, an HS communication signal processing unit 104, and a BC communication signal processing unit 105, as shown in Figure 2.

[0044] The switching control unit 103 includes a switch control driver 12. The switching control unit 103 determines whether to perform HS communication or BC communication between the CIS 2 and the AP 1.

[0045] When performing BC communication, the switching control unit 103 transmits a switch switching signal for close setting that causes a transition to a closed state using the dedicated line 5 to the switch 3. The switching control unit 103 closes the switch 3 with the switch switching signal for close setting and connects the communication line 31, thereby connecting the communication line 42 and the transceiver 102. As a result, the AP side BC communication signal transmitted from the transceiver 102 can be sent to the CIS 2, and the CIS side BC communication signal transmitted from the CIS 2 can be sent to the AP 1.

[0046] On the other hand, when performing HS communication, the switching control unit 103 transmits a switch switching signal for open setting that causes a transition to an open state using the dedicated line 5 to the switch 3. The switching control unit 103 opens the switch 3 and disconnects the communication line 31. As a result, when the HS negative signal in HS communication is transmitted through the communication line 42, the communication line 31 at the branched end disappears or becomes very short at the branch point 30. The impedance when looking at the AP 1 from the branch point 30 becomes substantially open, that is, infinite. Therefore, no reflected wave of the HS negative signal occurs, or even if reflection of the HS negative signal occurs at the cut-off point by the switch 3, the phase shift is suppressed, so that deterioration due to the reflected wave of the original HS negative signal can be greatly suppressed.

[0047] Here, the arrangement position of the switch 3 will be described. If the switch 3 is far from the branch point 30, the portion of the communication line 31 between them corresponds to a stub, and thus the signal of the HS communication may deteriorate due to the reflected wave. Therefore, the switch 3 is preferably arranged as close to the branch point 30 as possible. However, in practice, there may be cases where the switch 3 has to be arranged at a certain distance from the branch point 30. Thus, as an example, the switch 3 is preferably arranged at a position where the length of the portion from the branch point 30 of the communication line 31 to the switch 3 is about 1 / 60 wavelength or less of the fundamental frequency component of the transmission speed of the HS signal. However, this arrangement position is just a guideline, and preferably, the arrangement position of the switch 3 is determined in consideration of other factors such as the configuration of the signal processing device 100 and the characteristics of the switch 3. In addition, when the switch 3 has to be installed at a certain distance from the branch point 30, it is preferable to confirm by simulation or the like whether the deterioration of the HS negative signal due to the reflected wave generated in the stub caused by the separation of the switch 3 and the branch point 30 is acceptable in the applicable communication system.

[0048] As described above, when communication using the first signal is performed, the switch 3, which is the first switching unit, blocks the propagation of the first signal to the first branch line, and when communication using the second signal is performed, it allows the second signal to pass through the first branch line. Specifically, when communication using the first signal is performed, the switching control unit 103 controls the switch 3 to disconnect the first branch line, and when communication using the second signal is performed, it controls the switch 3 to connect the first branch line.

[0049] The receiver 101 has the differential amplifier 11 in FIG. 1. The receiver 101 receives the input of the HS positive signal sent via the communication line 41 and the input of the HS negative signal sent via the communication line 42. In the case of HS communication, the state of the switch 3 is open by the switching control unit 103, and the receiver 101 receives the HS negative signal with signal deterioration suppressed by the reflected wave in the communication line 31.

[0050] The receiver 101 generates an HS communication signal using the HS positive signal and the HS negative signal in the communication line 31. In this case, signal degradation due to reflected waves of the HS negative signal is suppressed, so the receiver 101 can accurately generate a noise-free HS communication signal. Subsequently, the receiver 101 outputs the HS communication signal to the HS communication signal processing unit 104.

[0051] The HS communication signal processing unit 104 receives the HS communication signal input from the receiver 101. The HS communication signal processing unit 104 then performs various signal processing on the input HS communication signal to generate image data. The HS communication signal processing unit 104 may also perform other functions such as subject estimation, recognition, and discrimination.

[0052] The transceiver 102 includes a BC transmission driver 13 and a BC reception driver 14. The transceiver 102 outputs the AP-side BC communication signal, which is a control signal from AP1 to CIS2, to the communication line 31 when switch 3 is closed. In this case, the AP-side BC communication signal is transmitted to CIS2 via the communication line 31 and the communication line 42.

[0053] Furthermore, the transceiver 102 receives the CIS-side BC communication signal, which is a control signal from CIS2 to AP1, from the communication line 31 when switch 3 is closed. The transceiver 102 then outputs the received CIS-side BC communication signal to the BC communication signal processing unit 105.

[0054] The BC communication signal processing unit 105 receives the CIS-side BC communication signal input from the transceiver 102. Then, the BC communication signal processing unit 105 makes changes such as settings according to the CIS-side BC communication signal.

[0055] <1.3. Signal Flow in Signal Processing Device> Figure 3 is a diagram showing the signal flow in a signal processing device according to the first embodiment. In Figure 3, the parts related to signal transmission and reception are mainly shown, and other parts are omitted.

[0056] As shown in Figure 3, CIS2 may be mounted on the CIS substrate 20. AP1 may also be mounted on the AP substrate 10. In this case, the branching point 30 is located on the AP substrate 10. The branching point 25 of CIS2 is located both on the CIS substrate 20 and within CIS2.

[0057] In the case of HS communication, switch 3 transitions to an open state upon receiving control from AP1. With switch 3 in the open state, the transmitter 201 of CIS2 transmits the HS positive signal and the HS negative signal to the receiver 101 of AP1.

[0058] The HS positive signal is sent to the receiver 101 via the communication line 41. The HS negative signal is sent to the receiver 101 via the communication line 42, without being affected by reflected waves due to the open switch 3 and the open stub of the communication line 31.

[0059] In the case of BC communication, switch 3 transitions to a closed state upon receiving control from AP1. With switch 3 in the closed state, the transceiver 202 of CIS2 transmits the CIS-side BC communication signal to the transceiver 102 of AP1. Conversely, the transceiver 102 of AP1 transmits the AP-side BC communication signal to the transceiver 202 of CIS2.

[0060] Since switch 3 is closed, both the CIS-side BC communication signal and the AP-side BC communication signal can be transmitted and received between transceiver 202 and transceiver 102 via communication line 26, the portion of communication line 42 between branching point 25 and branching point 30, and communication line 31.

[0061] <1.4. Transition of Connection State via HS Communication and BC Communication> Figure 4 is a sequence diagram showing the state of each location when switching between HS communication and BC communication. Period T1 is the period during which no communication takes place. Period T2 is the period during which HS communication takes place. Period T3 is the period during which BC communication takes place from AP1 to CIS2. Period T4 is the period during which BC communication takes place from CIS2 to AP1.

[0062] During period T1, the switch control driver 12 of the AP1's switching control unit 103 transmits an open setting switch switching signal to set switch 3 to an open state. If no communication is performed, switch 3 may be either open or closed, but here we will explain assuming that the switch control driver 12 sets switch 3 to open.

[0063] Figure 5 shows the signal flow when no communication is taking place. As shown in Figure 5, the BC receiving driver 23, branch point 25, branch point 30 of the transceiver 202 of CIS2 and the differential amplifier 11 of AP1 are connected to the ground voltage in CIS2. Also, the BC receiving driver 14 of the transceiver 102 of AP1 is connected to the ground voltage to which the communication line 31 is connected.

[0064] In this case, as shown in period T1 in Figure 4, the HS transmission driver 21 of the CIS2 transmitter 201 becomes high impedance. Also, the inverted HS transmission driver 22 of the CIS2 transmitter 201 becomes high impedance. Also, the BC transmission driver 13 of the AP1 transceiver 102 becomes high impedance. Also, the BC transmission driver 24 of the CIS2 transceiver 202 becomes high impedance. Furthermore, the HS positive voltage, which is the voltage of the communication line 41, drops to the ground voltage. Also, the HS negative voltage, which is the voltage of the communication line 42, drops to the ground voltage.

[0065] During the HS communication period T2, the switch control driver 12 of the AP1's switching control unit 103 transmits an open setting switch switching signal to set switch 3 to an open state.

[0066] Figure 6 shows the signal flow when performing HS communication. As shown in Figure 6, the HS positive signal output from the HS transmission driver 21 of the transmitter 201 of CIS2 is input to the differential amplifier 11 of the receiver 101 of AP1 via the communication line 41. The HS negative signal output from the inverting HS transmission driver 22 of the transmitter 201 of CIS2 is input to the differential amplifier 11 of the receiver 101 of AP1 via the communication line 42. Also, since switch 3 is open, the BC receiving driver 14 of the transceiver 102 of AP1 drops to the voltage of the ground to which the communication line 31 is connected.

[0067] In this case, as shown in period T2 of Figure 4, the HS transmission driver 21 of the CIS2 transmitter 201 outputs an HS positive signal. The inverted HS transmission driver 22 of the CIS2 transmitter 201 outputs an HS negative signal. The BC transmission driver 13 of the AP1 transceiver 102 becomes high impedance. The BC transmission driver 24 of the CIS2 transceiver 202 also becomes high impedance. The HS positive voltage, which is the voltage of the communication line 41, is the voltage of the HS positive signal output by the HS transmission driver 21 of the CIS2 transmitter 201. The HS negative voltage, which is the voltage of the communication line 42, is the voltage of the HS negative signal output by the inverted HS transmission driver 22 of the CIS2 transmitter 201.

[0068] During period T3, when BC communication is performed from AP1 to CIS2, the switch control driver 12 in the switching control unit 103 of AP1 transmits a switch switching signal to set switch 3 to the closed state.

[0069] Figure 7 shows the signal flow for BC communication from AP to CIS. As shown in Figure 7, the AP-side BC communication signal output from the BC transmission driver 13 of the AP1 transceiver 102 passes through the section from branch point 30 to branch point 25 of the communication lines 31 and 42 when switch 3 is closed. The AP-side BC communication signal is then input to the BC reception driver 23 of the CIS2 transceiver 202 via the communication line 26. Also, as shown in Figure 7, some components of the AP-side BC communication signal propagate from branch point 30 to the differential amplifier 11 of the AP1 receiver 101.

[0070] In this case, as shown in period T3 in Figure 4, the HS transmission driver 21 of the CIS2 transmitter 201 becomes high impedance. Also, the inverted HS transmission driver 22 of the CIS2 transmitter 201 becomes high impedance. On the other hand, the BC transmission driver 13 of the AP1 transceiver 102 outputs the AP-side BC communication signal. Also, the BC transmission driver 24 of the CIS2 transceiver 202 becomes high impedance. The HS positive voltage, which is the voltage of the communication line 41, is the voltage of the AP-side BC communication signal output by the BC transmission driver 13 of the AP1 transceiver 102. The HS negative voltage, which is the voltage of the communication line 42, is the voltage of the AP-side BC communication signal output by the BC transmission driver 13 of the AP1 transceiver 102.

[0071] During period T4, when BC communication is performed from CIS2 to AP1, the switch control driver 12 in the switching control unit 103 of AP1 transmits a switch switching signal to set switch 3 to the closed state.

[0072] Figure 8 shows the signal flow for BC communication from CIS to AP. As shown in Figure 8, the CIS-side BC communication signal output from the BC transmission driver 24 of the CIS2 transceiver 202 passes through the section from branch point 25 to branch point 30 of the communication lines 26 and 42. The CIS-side BC communication signal is then input to the BC reception driver 14 of the AP1 transceiver 102 via the communication line 31 with switch 3 in the closed state. In addition, as shown in Figure 8, some components of the CIS-side BC communication signal propagate from branch point 30 to the differential amplifier 11 of the AP1 receiver 101.

[0073] In this case, as shown in period T4 of Figure 4, the HS transmission driver 21 of the CIS2 transmitter 201 becomes high impedance. Also, the inverted HS transmission driver 22 of the CIS2 transmitter 201 becomes high impedance. Furthermore, the BC transmission driver 13 of the AP1 transceiver 102 becomes high impedance. On the other hand, the BC transmission driver 24 of the CIS2 transceiver 202 outputs the CIS-side BC communication signal. The HS positive voltage, which is the voltage of the communication line 41, becomes the voltage of the CIS-side BC communication signal output by the BC transmission driver 24 of the CIS2 transceiver 202. Also, the HS negative voltage, which is the voltage of the communication line 42, becomes the voltage of the CIS-side BC communication signal output by the BC transmission driver 24 of the CIS2 transceiver 202.

[0074] <1.5. Switch Switching and Communication Processing> Figure 9 is a flowchart of the switch switching and communication processing. Next, referring to Figure 9, the overall flow of the switch switching and communication processing will be explained.

[0075] The switching control unit 103 determines whether or not to perform HS communication (step S1).

[0076] When HS communication is performed (Step S1: Affirmative), the switching control unit 103 transmits an open setting switch switching signal to open the switch 3 (Step S2).

[0077] Transmitter 201 of CIS2 and receiver 101 of AP1 perform HS communication using two communication lines for differential transmission (step S3). Specifically, transmitter 201 outputs an HS positive signal to communication line 41 and an HS negative signal to communication line 42. Receiver 101 receives the HS positive signal via communication line 41 and the HS negative signal via communication line 42. Receiver 101 then generates an HS communication signal from the HS positive and HS negative signals. HS communication signal processing unit 104 performs signal processing on the HS communication signal. After that, the switch switching process and communication process proceed to step S6.

[0078] In contrast, when BC communication is performed (step S1: negative), the switching control unit 103 sends a switch switching signal for the close setting to close the switch 3 (step S4).

[0079] The transceiver 202 of CIS2 and the transceiver 102 of AP1 perform BC communication via one of the communication lines for differential transmission (step S5). For example, the transceiver 102 outputs the AP-side BC communication signal to the communication line 31 with switch 3 closed. The transceiver 202 receives input of the AP-side BC communication signal sent via communication line 31, the section of communication line 42 from branch point 25 to branch point 30, and communication line 26. In this case, a signal processing unit of CIS2 (not shown) performs signal processing on the AP-side BC communication signal. Alternatively, the transceiver 202 outputs the CIS-side BC communication signal to communication line 26. The transceiver 102 receives input of the CIS-side BC communication signal sent via communication line 26, the section of communication line 42 from branch point 30 to branch point 25, and communication line 31 with switch 3 closed. In this case, the BC communication signal processing unit 105 performs signal processing on the CIS-side BC communication signal. After that, the switch switching process and communication process proceed to step S6.

[0080] The switching control unit 103 determines whether to stop operation based on whether the power to the signal processing device 100 has been turned off (step S6). If operation is to continue (step S6: negative), the switch switching process and communication process return to step S1. Conversely, if operation is to stop (step S6: positive), the switch switching process and communication process are terminated.

[0081] <1.6. Effects> As described above, in this embodiment, AP1 and CIS2 of the signal processing device 100 communicate using differential transmission with two communication lines 41 and 42 for HS communication, and use the communication line 42 used for HS communication for BC communication. The signal processing device 100 has a branching point 30 for the communication of the other signal outside of AP1, and has a switch 3 at or near the branching point 30. AP1 opens switch 3 when performing HS communication and closes switch 3 when performing BC communication.

[0082] This makes it possible to suppress the effects of reflected waves generated when HS communication is performed, as the communication line 31 for BC communication after the branching point 30 becomes an open stub, thereby reducing the degradation of the HS communication signal waveform. Consequently, it is possible to maintain signal quality, achieve higher transmission rates and longer transmission distances, and improve communication performance.

[0083] <1.7. Modifications of the First Embodiment> Figure 10 is a diagram showing the signal flow in a signal processing device according to a modification of the first embodiment. The signal processing device 100 according to this modification will be described with reference to Figure 10.

[0084] The transmitter 201 of CIS2 and the receiver 101 of AP1 are connected by a single communication line 42. The communication line 42 branches off at branching point 25 and connects to the transceiver 202. The communication line 42 also branches off at branching point 30 and connects to the transceiver 102.

[0085] In this modified example, when performing HS communication, the switching control unit 103 transmits an open-setting switch switching signal to the switch 3 using the dedicated line 5, opening the switch 3 and disconnecting the communication line 31. This suppresses the degradation of the original HS communication signal due to reflected waves of the HS communication signal. When performing BC communication, the switching control unit 103 transmits a closed-setting switch switching signal to the switch 3 using the dedicated line 5, closing the switch 3 and connecting the communication line 42 and the transceiver 102.

[0086] With switch 3 open, the transmitter 201 outputs a single-ended HS communication signal to the communication line 42. The receiver 101 receives the single-ended signal output from the transmitter 201 via the communication line 42.

[0087] With switch 3 closed, transceiver 102 and transceiver 202 perform BC communication via communication line 26, the section of communication line 42 between branch point 25 and branch point 30, and communication line 31.

[0088] <1.8. Effects of Modified Version of the First Embodiment> As described above, in this modified version, CIS2 and AP1 perform HS communication using single-ended signals. Even in this configuration where HS communication is performed using single-ended signals and one communication line 42 is used, CIS2 and AP1 can perform BC communication using the communication line 42 by switching the switch 3. Furthermore, even in a configuration where HS communication is performed using one communication line 42, by performing HS communication with the switch 3 in an open state, the effects of reflected waves in HS communication can be suppressed, and the degradation of the signal waveform can be reduced. Therefore, it is possible to maintain signal quality, achieve higher transmission rates and longer transmission distances, and improve communication performance.

[0089] <2. Second Embodiment> <2.1. Signal Processing Device According to the Second Embodiment> Figure 11 is a diagram showing the signal flow in the signal processing device according to the second embodiment. The signal processing device 100 according to this embodiment will be described with reference to Figure 11. In Figure 11, the HS communication signal processing unit 104 and the BC communication signal processing unit 105, which are located downstream of the receiver 101 and the transceiver 102, are omitted. In this embodiment as well, the HS communication signal processing unit 104 and the BC communication signal processing unit 105 perform the same operations as in the first embodiment.

[0090] The CIS2 according to this embodiment has two transceivers 202A and 202B that transmit BC signals. Transceiver 202A is connected to communication line 41 at branch point 25A via communication line 26A. Transceiver 202B is connected to communication line 42 at branch point 25B via communication line 26B.

[0091] The communication line 41 is located outside AP1 and has a branching point 30A on the AP board 10. The communication line 31A that branches off from the communication line 41 at branching point 30A is connected to the transceiver 102 via a switch 3A.

[0092] Furthermore, the communication line 42 is located outside AP1 and has a branching point 30B on the AP board 10. The communication line 31B that branches off from the communication line 42 at branching point 30B is connected to the transceiver 102 via a switch 3B.

[0093] Here, branching point 30A is an example of a "second branching point," and the communication line 31A extending from branching point 30A to AP1 is an example of a "second branch line." Also, switch 3A is an example of a "second switching unit." Furthermore, branching point 30B is an example of a "first branching point," and the communication line 31B extending from branching point 30B to AP1 is an example of a "first branch line." Also, switch 3B is an example of a "first switching unit."

[0094] The switching control unit 103 is connected to switch 3A by dedicated line 5A and to switch 3B by dedicated line 5B. When performing HS communication, the switching control unit 103 transmits an open-setting switch switching signal to switches 3A and 3B using dedicated lines 5A and 5B, opening both switches 3A and 3B and disconnecting the communication lines 31A and 31B. This suppresses both the degradation of the original HS positive signal due to reflected waves of the HS positive signal and the degradation of the original HS negative signal due to reflected waves of the HS negative signal.

[0095] When transceiver 202A performs BC communication, the switching control unit 103 sends a switch switching signal to close the switch to switch 3A via the dedicated line 5A, closing the switch 3A and connecting the communication line 41 to transceiver 102. Similarly, when transceiver 202B performs BC communication, the switching control unit 103 sends a switch switching signal to close the switch to switch 3B via the dedicated line 5B, closing the switch 3B and connecting the communication line 42 to transceiver 102.

[0096] With both switches 3A and 3B open, the transmitter 201 outputs an HS positive signal to the communication line 41 and an HS negative signal to the communication line 42. The receiver 101 receives the HS positive signal output from the transmitter 201 via the communication line 41 and receives the HS negative signal via the communication line 42.

[0097] Transceiver 102 and transceiver 202A communicate via communication line 26A, the section of communication line 41 between branch point 25A and branch point 30A, and communication line 31A when switch 3A is closed. Transceiver 102 and transceiver 202B communicate via communication line 26B, the section of communication line 42 between branch point 25B and branch point 30B, and communication line 31B when switch 3B is closed.

[0098] The BC communication signals transmitted and received by transceiver 102 and transceiver 202A, and the BC communication signals transmitted and received by transceiver 102 and transceiver 202B are examples of the "second signal." That is, the second signal transmitted and received by transceiver 102 and transceiver 202A is transmitted over the portion of the first communication line from the first communication section to the first branch point and over the first branch line. The second signal transmitted and received by transceiver 102 and transceiver 202B is transmitted over the portion of the second communication line from the first communication section to the second branch point and over the second branch line.

[0099] Furthermore, the second switching unit, switch 3B, is located near the second branching point on the second branch line or at the second branching point itself. When communication using the first signal is performed, switch 3B blocks the propagation of the differential signal of the first signal to the second branch line, and when communication using the second signal is performed, it allows the second signal to pass through the second branch line.

[0100] In this case, the BC communication signal can be a differential signal. For example, transceiver 102 and transceiver 202A can transmit the positive signal of the BC communication differential signal, and transceiver 102 and transceiver 202B can transmit the negative signal of the BC communication differential signal.

[0101] In other words, the first communication unit and the second communication unit transmit and receive differential signals of the second signal using both the portion of the first communication line from the first communication unit to the first branch point and the first branch line, and the portion of the second communication line from the first communication unit to the second branch point and the second branch line.

[0102] In this embodiment, the switching control unit 103 controls the switch 3A or 3B connected to the communication side of the transceiver 202A and transceiver 202B to be in a closed state. That is, the first switching unit and the second switching unit simultaneously block the propagation of the differential signal of the first signal to the first branch line and block the propagation of the differential signal of the first signal to the second branch line. Furthermore, the first switching unit and the second switching unit can enable the passage of the second signal on the first branch line and the passage of the second signal on the second branch line at different timings.

[0103] However, the switching control unit 103 is not limited to this, and may simultaneously control both switches 3A and 3B to the closed state in the case of either BC communication by transceiver 202A or BC communication by transceiver 202B. In particular, when the BC communication signal is a differential signal, it is preferable for the switching control unit 103 to control both to the closed state simultaneously. That is, the first switching unit and the second switching unit simultaneously block the propagation of the differential signal of the first signal to the first branch line and block the propagation of the differential signal of the first signal to the second branch line. Furthermore, the first switching unit and the second switching unit can simultaneously allow the passage of the second signal on the first branch line and the passage of the second signal on the second branch line.

[0104] <2.2. Effects> As explained above, in this modified configuration, the transceiver 202A of CIS2 and the transceiver 102 of AP1 perform BC communication using the communication line 41, and the transceiver 202B and the transceiver 102 perform BC communication using the communication line 42. Even if both of the two communication lines 41 and 42 for differential signals are used for BC communication, the effects of reflected waves in HS communication can be suppressed by performing HS communication between CIS2 and AP1 with both switches 3A and 3B open. Therefore, even with such a configuration, it is possible to maintain signal quality, achieve higher transmission rates and longer transmission distances, and improve communication performance.

[0105] <2.3. Modification of the Second Embodiment> Figure 12 is a diagram showing the signal flow in a signal processing device according to a modification of the second embodiment. The signal processing device 100 according to this modification will be described with reference to Figure 12.

[0106] AP1 in this modified configuration includes a transceiver 102A and a transceiver 102B, each performing BC communication. Transceiver 102A is connected to communication line 41 via communication line 31A on which switch 3A is located. Transceiver 102B is connected to communication line 42 via communication line 31B on which switch 3B is located.

[0107] In this modified example, when performing HS communication, the switching control unit 103 transmits an open-setting switch switching signal to switches 3A and 3B using dedicated lines 5A and 5B, thereby opening switches 3A and 3B. This makes it possible to suppress both the degradation of the original HS positive signal due to the reflected wave of the HS positive signal and the degradation of the original HS negative signal due to the reflected wave of the HS negative signal.

[0108] Furthermore, when transceiver 202A performs BC communication, the switching control unit 103 transmits a switch switching signal to close the switch to switch 3A using the dedicated line 5A, closing the switch 3A and connecting the communication line 41 to transceiver 102A. Furthermore, when transceiver 202B performs BC communication, the switching control unit 103 transmits a switch switching signal to close the switch to switch 3B using the dedicated line 5B, closing the switch 3B and connecting the communication line 42 to transceiver 102B.

[0109] With both switches 3A and 3B open, the transmitter 201 outputs an HS positive signal to the communication line 41 and an HS negative signal to the communication line 42. The receiver 101 receives the HS positive signal output from the transmitter 201 via the communication line 41 and the HS negative signal output from the transmitter 201 via the communication line 42.

[0110] Transceiver 102A and transceiver 202A communicate via communication line 26A, the section of communication line 41 between branch point 25A and branch point 30A, and communication line 31A when switch 3A is closed. Transceiver 102B and transceiver 202B communicate via communication line 26B, the section of communication line 42 between branch point 25B and branch point 30B, and communication line 31B when switch 3B is closed.

[0111] In this case, the BC communication between transceiver 102A and transceiver 202A and the BC communication between transceiver 102B and transceiver 202B can transmit and receive different signals. That is, the first communication unit and the second communication unit can transmit and receive different second signals in the portion of the first communication line from the first communication unit to the first branch point and the first branch line, and in the portion of the second communication line from the first communication unit to the second branch point and the second branch line.

[0112] <2.4. Effects of Modified Version of the Second Embodiment> As described above, AP1 in this modified version performs BC communication with the transceiver 202A of CIS2 via the communication line 41 using the transceiver 102A, and performs BC communication with the transceiver 202B of CIS2 via the communication line 42 using the transceiver 102B. In this way, even with a configuration in which BC communication using the communication line 41 and BC communication using the communication line 42 are separated, CIS2 and AP1 can perform BC communication using the communication lines 41 and 42 by switching switches 3A and 3B. Furthermore, CIS2 and AP1 can perform HS communication by keeping both switches 3A and 3B open, thereby suppressing the effects of reflected waves in HS communication. Therefore, even with such a configuration, it is possible to maintain signal quality, achieve higher transmission rates and longer transmission distances, and improve communication performance.

[0113] <3. Third Embodiment> <3.1. Signal Processing Device According to the Third Embodiment> Figure 13 is a diagram showing the signal flow in the signal processing device according to the third embodiment. The signal processing device 100 according to this embodiment will be described with reference to Figure 13.

[0114] In this embodiment, AP1 does not necessarily have a dedicated line 5 extending from the switching control unit 103 to the switch 3. When HS communication is performed, the switching control unit 103 transmits an open-setting switch switching signal to the switch 3 using the communication line 31 for BC communication, as shown in signal transmission process P1, opening the switch 3 and disconnecting the communication line 31. This suppresses the degradation of the original HS negative signal due to reflected waves of the HS negative signal. When BC communication is performed, the switching control unit 103 transmits a closed-setting switch switching signal to the switch 3 using the communication line 31 for BC communication, closing the switch 3 and connecting the communication line 42 and the transceiver 102. In this way, the switching control unit 103 transmits a switch switching signal to the switch 3 using the communication line 31 to control the switching of the switch 3.

[0115] With switch 3 open, transmitter 201 outputs an HS positive signal to communication line 41 and an HS negative signal to communication line 42. Receiver 101 receives the HS positive signal output from transmitter 201 via communication line 41 and the HS negative signal via communication line 42.

[0116] With switch 3 closed, transceiver 102 and transceiver 202 perform BC communication via communication line 26, the section of communication line 42 between branch point 25 and branch point 30, and communication line 31.

[0117] <3.2. Effects> As described above, the switching control unit 103 according to this embodiment transmits a switch switching signal to the switch 3 using the BC communication line 31. Even with this configuration, where the BC communication line 31 is used for switching control of the switch 3, CIS2 and AP1 can reduce signal waveform degradation due to reflected waves by performing HS communication with the switch 3 in an open state. Therefore, it is possible to maintain signal quality, achieve higher transmission rates and longer transmission distances, and improve communication performance.

[0118] <3.3. Modification of the Third Embodiment> Figure 14 is a diagram showing the signal flow in a signal processing device according to a modification of the third embodiment. The signal processing device 100 according to this modification will be described with reference to Figure 14.

[0119] The modified CIS2 has a switching control unit 203. When HS communication is performed, the switching control unit 203 transmits a switch switching signal for the closed setting to the receiver 101 of AP1 via the transmitter 201 and communication lines 41 and 42. When BC communication is performed, the switching control unit 203 transmits a switch switching signal for the open setting to the receiver 101 of AP1 via the transmitter 201 and communication line 41.

[0120] The receiver 101 is connected to the transceiver 102. As shown in signal transmission process P11, the receiver 101 forwards the switch switching signal received from the switching control unit 203 to the transceiver 102. As shown in signal transmission process P12, the transceiver 102 transmits the switch switching signal to the switch 3 using the BC communication line 31. As a result, the switch 3 transitions to an open or closed state according to the switch switching signal output by the switching control unit 203 of the CIS2.

[0121] With switch 3 open, transmitter 201 outputs an HS positive signal to communication line 41 and an HS negative signal to communication line 42. Receiver 101 receives the HS positive signal output from transmitter 201 via communication line 41 and the HS negative signal via communication line 42.

[0122] With switch 3 closed, transceiver 102 and transceiver 202 perform BC communication via communication line 26, the section of communication line 42 between branch point 25 and branch point 30, and communication line 31.

[0123] In this manner, when communication using the first signal is performed, the switching control unit 203 transmits a switch switching signal to the second communication unit AP1 to disconnect the first branch line. When communication using the second signal is performed, the switching control unit 203 transmits a switch switching signal to the second communication unit AP1 to connect the first branch line. The second communication unit AP1 then transmits the switch switching signal received from the switching control unit 203 to the switch 3 to disconnect or connect the first branch line.

[0124] <3.4. Effects of Modified Version of the Third Embodiment> As described above, the switching control unit 203 of the CIS2 in this modified version transmits a switch switching signal to AP1, and transmits the switch switching signal to switch 3 via AP1 using the BC communication line 31. In this way, even with a configuration in which the CIS2 is the source point of the switch switching signal, the degradation of the signal waveform due to reflected waves can be reduced between the CIS2 and AP1 by performing HS communication with switch 3 in an open state. Therefore, it is possible to maintain signal quality, achieve high transmission rates and long transmission distances, and improve communication performance.

[0125] <4. Fourth Embodiment> <4.1. Signal Processing Device According to the Fourth Embodiment> Figure 15 is a diagram showing the signal flow in the signal processing device according to the fourth embodiment. The signal processing device 100 according to this embodiment will be described with reference to Figure 15. In the following description, the operation of each part, which is the same as in the first embodiment, may be omitted.

[0126] In this embodiment, a capacitor 43 is located near the receiver 101 in the communication line 41. In this embodiment, a capacitor 44 is located near the receiver 101 in the communication line 42. The capacitor 44 is located at least on the receiver 101 side of the branching point 30. That is, the capacitor 44 is located between the first branching point in the first communication line and the second communication unit AP1.

[0127] Figure 16 is a diagram illustrating the signal flow in a signal processing device according to the fourth embodiment. State 301 shows the signal flow when capacitors 43 and 44 are not provided. State 302 shows the signal flow of the signal processing device 100 with capacitors 43 and 44 provided.

[0128] If capacitors 43 and 44 are not provided, as shown in state 301, the HS communication signal flows into the receiver 101 of AP1 via the communication line 42. Also, the BC communication signal from CIS2 to AP1 flows to the transceiver 102 via the communication line 31 through the branching point 30, and also propagates to AP1 via the communication line 42. Similarly, the BC communication signal from AP1 to CIS2 is sent to CIS2 via the branching point 30, and also propagates to AP1 via the communication line 42. In this way, the signal component of the BC communication signal is split into two, so in state 301, the amplitude of the BC communication signal transmitted to the transceiver 102 or 202 is attenuated.

[0129] On the other hand, in the signal processing device 100 according to this embodiment, as shown in state 302, the HS communication signal has a high frequency, so it passes through capacitors 43 and 44 and flows into the receiver 101 of AP1 via the communication line 42. In contrast, the BC communication signal has a low frequency, so the impedance from capacitors 43 and 44 to AP1 is high for the BC communication signal, making it difficult for it to pass through capacitor 44. Therefore, the BC communication signal is transmitted to the transceiver 102 or 202 without the signal components being separated, so in state 302, the amplitude of the BC communication signal transmitted to the transceiver 102 or 202 does not decrease. For this reason, the transceiver 102 and the transceiver 202 can perform BC communication using a signal with no amplitude reduction.

[0130] <4.2. Effects> As described above, in the signal processing device 100 according to this embodiment, capacitors 43 and 44 are arranged near the receiver 101 of the communication lines 41 and 42. This reduces signal degradation in BC communication between the transceiver 102 and the transceiver 202. Therefore, it is possible to maintain signal quality, achieve higher transmission rates and longer transmission distances, and improve communication performance.

[0131] <5. Fifth Embodiment> <5.1. Signal Processing Device According to the Fifth Embodiment> Figure 17 is a diagram showing the signal flow in the signal processing device according to the fifth embodiment. The signal processing device 100 according to this embodiment will be described with reference to Figure 17. In the following description, the operation of each part, which is the same as in the first embodiment, may be omitted.

[0132] In this embodiment, the signal processing device 100 has an inductor 6 instead of a switch 3 on the communication line 31 extending from the branching point 30 to the transceiver 102. The HS signal has a frequency band of high-frequency components, and the BS signal has a frequency band of low-frequency components, and the HS signal and the BS signal have different frequency bands. The inductor 6 has an inductance such that at the branching point 30, the communication line 31 side has high impedance when viewed from the perspective of the HS communication signal, and low impedance when viewed from the perspective of the BC communication signal. Thus, the first switching unit is an inductor 6 that has an inductance that does not allow the first signal to pass through, but allows the second signal to pass through.

[0133] By arranging an inductor 6 with such inductance, when the HS signal flows through the communication line 42, the inductor 6 can be considered equivalent to the switch 3 being open with respect to the HS signal. Therefore, reflected waves to the HS signal can be suppressed.

[0134] Furthermore, when a BC signal flows through the communication line 42, the inductor 6 can be considered equivalent to the switch 3 being in a closed state with respect to the BC signal. Therefore, the transceiver 102 and the transceiver 202 can perform BC communication via the communication line 26, the portion of the communication line 42 between branching point 25 and branching point 30, and the communication line 31.

[0135] <5.2. Effects> As described above, the signal processing device 100 according to this embodiment can use the inductor 6 to disconnect the communication line 31 connecting the branching point 30 to the transceiver 102 for HS communication and connect it for BC communication. In this way, when performing HS communication, the influence of reflected waves generated by the communication line 31 for BC communication after the branching point 30 becoming an open stub can be suppressed, and the degradation of the signal waveform of HS communication can be reduced. Therefore, it is possible to maintain signal quality, achieve higher transmission rates and longer transmission distances, and improve communication performance.

[0136] <5.3. Modification of the Fifth Embodiment> Figure 18 is a diagram showing the signal flow in a signal processing device according to a modification of the fifth embodiment. The signal processing device 100 according to this modification will be described with reference to Figure 18.

[0137] In this modified example, a capacitor 43 is placed near the receiver 101 in the communication line 41. In addition, a capacitor 44 is placed near the receiver 101 in the communication line 42 according to this embodiment. The capacitor 44 is provided at least on the receiver 101 side of the branching point 30.

[0138] Figure 19 is a diagram illustrating the signal flow in a signal processing device according to a modified example of the fifth embodiment. Since a capacitor 44 is placed in the communication line 42, the impedance from the capacitor 44 to AP1 is high for the BC communication signal, and as shown by arrow Q1, the BC communication signal cannot pass through the capacitor 44. Therefore, the BC communication signal is sent to the transceiver 102 or 202 via the communication line 31 without any reduction in amplitude.

[0139] Furthermore, an inductor 6 is placed on the communication line 31 extending from the branching point 30 to the transceiver 102. The inductor 6 has an inductance such that the communication line 31 branched at the branching point 30 has a high impedance when viewed from the perspective of the HS communication signal and a low impedance when viewed from the perspective of the BC communication signal. As a result, similar to the fifth embodiment, the HS communication signal does not pass through the inductor 6 as shown by arrow Q2, and the influence of reflected waves on the HS signal can be suppressed.

[0140] <5.4. Effects of Modified Form of the Fifth Embodiment> As described above, in the signal processing device 100 according to this embodiment, an inductor 6 is placed between the branching point 30 and the transceiver 102, and a capacitor 44 is placed between the branching point 30 and the receiver 101. This makes it possible to suppress the effects of reflected waves that occur when HS communication is performed, as the communication line 31 for BC communication after the branching point 30 becomes an open stub, thereby reducing the degradation of the signal waveform of HS communication. It also makes it possible to reduce the degradation of the BC communication signal between the transceiver 102 and the transceiver 202. Therefore, it is possible to maintain signal quality, achieve higher transmission rates and longer transmission distances, and improve communication performance.

[0141] <6. Examples of Application to Endoscopic Surgical Systems> The technology disclosed herein (this technology) can be applied to various products. For example, the technology disclosed herein may be applied to an endoscopic surgical system.

[0142] Figure 20 shows an example of a schematic configuration of an endoscopic surgical system.

[0143] Figure 20 illustrates a surgeon (physician) 11131 performing surgery on a patient 11132 on a patient bed 11133 using an endoscopic surgical system 11000. As shown in the figure, the endoscopic surgical system 11000 consists of an endoscope 11100, other surgical instruments 11110 such as a pneumoperitoneum tube 11111 and an energy treatment device 11112, a support arm device 11120 for supporting the endoscope 11100, and a cart 11200 equipped with various devices for endoscopic surgery.

[0144] The endoscope 11100 consists of a barrel 11101, the tip of which is inserted into the body cavity of the patient 11132 for a predetermined length, and a camera head 11102 connected to the base end of the barrel 11101. In the illustrated example, the endoscope 11100 is shown as a so-called rigid endoscope having a rigid barrel 11101, but the endoscope 11100 may also be configured as a so-called flexible endoscope having a flexible barrel.

[0145] An opening into which an objective lens is fitted is provided at the tip of the endoscope tube 11101. A light source device 11203 is connected to the endoscope 11100, and the light generated by the light source device 11203 is guided to the tip of the endoscope tube 11101 by a light guide extending inside the endoscope tube 11101, and is irradiated through the objective lens towards the object to be observed inside the body cavity of the patient 11132. The endoscope 11100 may be a straight-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

[0146] The camera head 11102 contains an optical system and an image sensor. Reflected light from the object being observed (observation light) is focused onto the image sensor by the optical system. The image sensor converts the observation light into electrical signals, generating an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observed image. This image signal is transmitted as RAW data to the camera control unit (CCU) 11201.

[0147] The CCU 11201 is composed of a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and other components, and comprehensively controls the operation of the endoscope 11100 and the display device 11202. Furthermore, the CCU 11201 receives an image signal from the camera head 11102 and performs various image processing operations on that image signal, such as development processing (demosaic processing), to display an image based on that image signal.

[0148] The display device 11202 displays an image based on an image signal that has been processed by the CCU 11201, under control from the CCU 11201.

[0149] The light source device 11203 consists of a light source such as an LED (Light Emitting Diode) and supplies illumination light to the endoscope 11100 when photographing the surgical area, etc.

[0150] The input device 11204 is an input interface for the endoscopic surgical system 11000. The user can input various types of information and instructions to the endoscopic surgical system 11000 via the input device 11204. For example, the user can input instructions to change the imaging conditions (type of light, magnification, focal length, etc.) of the endoscope 11100.

[0151] The treatment instrument control device 11205 controls the drive of the energy treatment instrument 11112 for purposes such as tissue cauterization, incision, or blood vessel sealing. The insufflation device 11206 injects gas into the body cavity of the patient 11132 via the insufflation tube 11111 to inflate the body cavity for the purpose of securing a field of view by the endoscope 11100 and securing the operator's workspace. The recorder 11207 is a device capable of recording various information related to the surgery. The printer 11208 is a device capable of printing various information related to the surgery in various formats such as text, images, or graphs.

[0152] The light source device 11203 that supplies illumination light to the endoscope 11100 when photographing the surgical area can be configured as a white light source consisting of, for example, an LED, a laser light source, or a combination thereof. When the white light source is configured as a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, so the white balance of the captured image can be adjusted in the light source device 11203. In this case, it is also possible to capture images corresponding to each of the RGB colors in time-division by irradiating the observation target with laser light from each of the RGB laser light sources in time-division and controlling the drive of the image sensor of the camera head 11102 in synchronization with the irradiation timing. According to this method, a color image can be obtained without providing a color filter on the image sensor.

[0153] Furthermore, the light source device 11203 may be controlled to change the intensity of the light it outputs at predetermined time intervals. By controlling the drive of the image sensor of the camera head 11102 in synchronization with the timing of the change in light intensity, images can be acquired in time-division order, and these images can be combined to generate high dynamic range images without so-called black crushing and white clipping.

[0154] Furthermore, the light source device 11203 may be configured to supply light in a predetermined wavelength band corresponding to special light observation. In special light observation, for example, by utilizing the wavelength dependence of light absorption in body tissue and irradiating with narrow-band light compared to the irradiation light used during normal observation (i.e., white light), so-called narrow-band imaging is performed to image predetermined tissues such as blood vessels on the surface of mucosa with high contrast. Alternatively, in special light observation, fluorescence observation may be performed to obtain an image from fluorescence generated by irradiation with excitation light. In fluorescence observation, excitation light is irradiated onto body tissue and fluorescence from the body tissue is observed (autofluorescence observation), or a reagent such as indocyanine green (ICG) is injected into body tissue and excitation light corresponding to the fluorescence wavelength of the reagent is irradiated onto the body tissue to obtain a fluorescence image. The light source device 11203 may be configured to supply narrow-band light and / or excitation light corresponding to such special light observation.

[0155] Figure 21 is a block diagram showing an example of the functional configuration of the camera head and CCU.

[0156] The camera head 11102 includes a lens unit 11401, an imaging unit 11402, a drive unit 11403, a communication unit 11404, and a camera head control unit 11405. The CCU 11201 includes a communication unit 11411, an image processing unit 11412, and a control unit 11413. The camera head 11102 and the CCU 11201 are connected to each other via a transmission cable 11400 so that they can communicate with each other.

[0157] The lens unit 11401 is an optical system provided at the connection point with the lens barrel 11101. Observation light taken in from the tip of the lens barrel 11101 is guided to the camera head 11102 and then incident on the lens unit 11401. The lens unit 11401 is composed of a combination of multiple lenses, including a zoom lens and a focus lens.

[0158] The imaging unit 11402 may consist of one image sensor (a so-called single-chip type) or multiple image sensors (a so-called multi-chip type). If the imaging unit 11402 is configured as a multi-chip type, for example, each image sensor may generate image signals corresponding to RGB, and these may be combined to obtain a color image. Alternatively, the imaging unit 11402 may be configured to have a pair of image sensors for acquiring image signals for the right eye and left eye, respectively, corresponding to 3D (dimensional) display. By performing 3D display, the surgeon 11131 can more accurately grasp the depth of the biological tissue in the surgical area. In addition, if the imaging unit 11402 is configured as a multi-chip type, multiple lens units 11401 may be provided corresponding to each image sensor.

[0159] Furthermore, the imaging unit 11402 does not necessarily have to be located on the camera head 11102. For example, the imaging unit 11402 may be located inside the lens barrel 11101, directly behind the objective lens.

[0160] The drive unit 11403 is composed of actuators and, under control from the camera head control unit 11405, moves the zoom lens and focus lens of the lens unit 11401 along the optical axis by a predetermined distance. This allows the magnification and focus of the image captured by the imaging unit 11402 to be adjusted as appropriate.

[0161] The communication unit 11404 is composed of communication devices for sending and receiving various types of information with the CCU 11201. The communication unit 11404 transmits the image signal obtained from the imaging unit 11402 as RAW data to the CCU 11201 via the transmission cable 11400.

[0162] Furthermore, the communication unit 11404 receives a control signal from the CCU 11201 to control the drive of the camera head 11102 and supplies it to the camera head control unit 11405. The control signal includes information about imaging conditions, such as information to specify the frame rate of the captured image, information to specify the exposure value at the time of imaging, and / or information to specify the magnification and focus of the captured image.

[0163] The imaging conditions such as frame rate, exposure value, magnification, and focus may be specified by the user as appropriate, or they may be automatically set by the control unit 11413 of the CCU 11201 based on the acquired image signal. In the latter case, the endoscope 11100 is equipped with so-called AE (Auto Exposure), AF (Auto Focus), and AWB (Auto White Balance) functions.

[0164] The camera head control unit 11405 controls the driving of the camera head 11102 based on the control signal received from the CCU 11201 via the communication unit 11404.

[0165] The communication unit 11411 is comprised of a communication device for sending and receiving various types of information with the camera head 11102. The communication unit 11411 receives image signals transmitted from the camera head 11102 via the transmission cable 11400.

[0166] Furthermore, the communication unit 11411 transmits control signals to the camera head 11102 to control the driving of the camera head 11102. Image signals and control signals can be transmitted by telecommunications, optical communications, etc.

[0167] The image processing unit 11412 performs various image processing operations on the image signal, which is RAW data transmitted from the camera head 11102.

[0168] The control unit 11413 performs various controls related to imaging the surgical area, etc., by the endoscope 11100, and the display of the images obtained from imaging the surgical area, etc. For example, the control unit 11413 generates a control signal to control the driving of the camera head 11102.

[0169] Furthermore, the control unit 11413 displays the captured image showing the surgical area, etc., on the display device 11202 based on the image signal processed by the image processing unit 11412. At this time, the control unit 11413 may recognize various objects in the captured image using various image recognition technologies. For example, the control unit 11413 can recognize surgical instruments such as forceps, specific biological sites, bleeding, mist when using the energy treatment device 11112, etc., by detecting the shape and color of the edges of objects included in the captured image. When the control unit 11413 displays the captured image on the display device 11202, it may use the recognition results to superimpose various surgical support information onto the image of the surgical area. By superimposing the surgical support information and presenting it to the surgeon 11131, the burden on the surgeon 11131 can be reduced, and the surgeon 11131 can proceed with the surgery reliably.

[0170] The transmission cable 11400 connecting the camera head 11102 and the CCU 11201 is an electrical signal cable compatible with electrical signal communication, an optical fiber compatible with optical communication, or a composite cable thereof.

[0171] In the illustrated example, communication was performed via a wired connection using a transmission cable 11400, but communication between the camera head 11102 and the CCU 11201 may be performed wirelessly.

[0172] The above describes an example of an endoscopic surgical system to which the technology described herein may be applied. The technology described herein can be applied to the imaging unit 11402 of the camera head 11102, etc., among the configurations described above. By applying the technology described herein to the imaging unit 11402 of the camera head 11102, the signal quality is improved and clearer surgical images can be obtained, so that the surgeon 11131 can reliably confirm the surgical area.

[0173] While an endoscopic surgical system has been described here as an example, the technology described herein may also be applied to other systems, such as microsurgical systems.

[0174] Furthermore, while the above embodiments described a system including a CIS2 and AP1 mounted on a camera as one of the signal superposition systems, signal superposition systems that transmit two types of signals to different destinations through a single line are used in a variety of other fields. The technologies described in each embodiment and its modifications are applicable to any signal processing device having such a signal superposition system.

[0175] While embodiments of this disclosure have been described above, the technical scope of this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of this disclosure. Furthermore, components from different embodiments and modifications may be combined as appropriate.

[0176] Furthermore, the effects described herein are merely illustrative and not limited to those described herein, and other effects may also occur.

[0177] Furthermore, this technology can also take the following configurations: (1) A signal processing device comprising: a first communication unit and a second communication unit that communicate using first and second signals of different types; a first communication line that connects the first communication unit and the second communication unit and transmits the first signal; a first branch line that branches off at a first branch point in the first communication line located outside the second communication unit and connects to the second communication unit, and transmits the second signal together with the portion of the first communication line from the first communication unit to the first branch point; and a first switching unit located near or at the first branch point on the first branch line, which, when communication using the first signal is performed, blocks the propagation of the first signal to the first branch line, and when communication using the second signal is performed, allows the second signal to pass through the first branch line. (2) The signal processing device according to (1) above, wherein the first communication unit and the second communication unit communicate using first and second signals with different transmission speeds. (3) The signal processing device according to (1) or (2), wherein the first communication unit and the second communication unit are connected together with the first communication line by a second communication line, and the differential signal of the first signal is transmitted and received using both the first communication line and the second communication line. (4) The signal processing device according to (3), further comprising: a second branch line that branches off at a second branch point in the second communication line located outside the second communication unit and connects to the second communication unit, and transmits the second signal via the portion of the second communication line from the first communication unit to the second branch point; and a second switching unit located near or at the second branch point on the second branch line, which, when communication using the second signal is performed, blocks the propagation of the differential signal of the first signal to the second branch line, and when communication using the second signal is performed, allows the second signal to pass through the second branch line. (5) The signal processing apparatus according to (4), wherein the first communication unit and the second communication unit transmit and receive differential signals of the second signal using both the portion of the first communication line from the first communication unit to the first branch point and the first branch line, and the portion of the second communication line from the first communication unit to the second branch point and the second branch line.(6) The signal processing device according to (4), wherein the first communication unit and the second communication unit transmit and receive different second signals on the portion of the first communication line from the first communication unit to the first branch point and the first branch line, and on the portion of the second communication line from the first communication unit to the second branch point and the second branch line. (7) The signal processing device according to any one of (4) to (6), wherein the first switching unit and the second switching unit simultaneously block the propagation of the differential signal of the first signal to the first branch line and block the propagation of the differential signal of the first signal to the second branch line, and also simultaneously allow the passage of the second signal on the first branch line and the passage of the second signal on the second branch line. (8) The signal processing device according to (4), wherein the first switching unit and the second switching unit simultaneously block the propagation of the differential signal of the first signal to the first branch line and block the propagation of the differential signal of the first signal to the second branch line, and also enable the passage of the second signal through the first branch line and the passage of the second signal through the second branch line at different timings. (9) The signal processing device according to any one of (1) to (8), wherein the first switching unit is a switch for disconnecting or connecting the first branch line, and the second communication unit is a switching control unit that controls the switch to disconnect the first branch line when communication using the first signal is performed, and to connect the first branch line when communication using the second signal is performed. (10) The signal processing device according to (9), wherein the switching control unit transmits a switch switching signal to the switch to control the switching of the switch using the first branch line. (11) The signal processing device according to any one of (1) to (8) above, wherein the first switching unit is a switch for disconnecting or connecting the first branch line, the first communication unit includes a switching control unit that transmits a switch switching signal for disconnecting the first branch line to the second communication unit when communication using the first signal is performed, and transmits a switch switching signal for connecting the first branch line to the second communication unit when communication using the second signal is performed, and the second communication unit transmits the switch switching signal received from the first communication unit to the switch for disconnecting or connecting the first branch line.(12) The signal processing device according to any one of (1) to (8), wherein the first switching unit is an inductor having an inductance that does not allow the first signal to pass through and allows the second signal to pass through. (13) The signal processing device according to any one of (1) to (12), wherein a capacitor is located between the first branch point and the second communication unit in the first communication line. (14) A signal processing board having a communication unit that communicates using first and second signals of different types; a first communication line that transmits the first signal to the communication unit; a first branch line that branches off at a first branch point in the first communication line located outside the communication unit and connects to the communication unit, and transmits the second signal together with the portion of the first communication line from the communication unit to the first branch point on the opposite side of the communication unit; and a switching unit located near or at the first branch point on the first branch line, which, when communication using the first signal is performed, blocks the propagation of the first signal to the first branch line, and when communication using the second signal is performed, allows the second signal to pass through the first branch line. (15) A signal processing method by a first communication unit and a second communication unit that communicate using different types of first and second signals, wherein the first communication unit and the second communication unit transmit the first signal on a first communication line connecting the first communication unit and the second communication unit, a first branch line that branches off at a first branch point in the first communication line located outside the second communication unit and connects to the second communication unit, and the second signal is transmitted on the portion of the first communication line from the first communication unit to the first branch point, and when communication using the first signal is performed, the propagation of the first signal to the first branch line is blocked near the first branch point on the first branch line or at the first branch point, and when communication using the second signal is performed, the signal processing method is performed to allow the second signal to pass through the first branch line.

[0178] 1 AP 2 CIS 3, 3A, 3B Switch 5, 5A, 5B Dedicated Line 6 Inductor 11 Differential Amplifier 12 Switch Control Driver 13 BC Transmitter Driver 14 BC Receiver Driver 21 HS Transmitter Driver 22 Inverting HS Transmitter Driver 23 BC Receiver Driver 24 BC Transmitter Driver 25, 25A, 25B, 30, 30A, 30B Branch Point 26, 31, 41, 42 Communication Line 43, 44 Capacitor 100 Signal Processing Unit 101 Receiver 102, 102A, 102B Transceiver 103 Switching Control Unit 104 HS Communication Signal Processing Unit 105 BC Communication Signal Processing Unit 201 Transmitter 202, 202A, 202B Transceiver

Claims

1. A signal processing device comprising: a first communication unit and a second communication unit that communicate using first and second signals of different types; a first communication line connecting the first communication unit and the second communication unit and transmitting the first signal; a first branch line that branches off at a first branch point in the first communication line located outside the second communication unit and connects to the second communication unit, and transmits the second signal together with the portion of the first communication line from the first communication unit to the first branch point; and a first switching unit located near or at the first branch point on the first branch line, which, when communication using the first signal is performed, blocks the propagation of the first signal to the first branch line, and when communication using the second signal is performed, allows the second signal to pass through the first branch line.

2. The signal processing apparatus according to claim 1, wherein the first communication unit and the second communication unit communicate using the first signal and the second signal, which have different transmission speeds.

3. The signal processing apparatus according to claim 1, wherein the first communication unit and the second communication unit are connected together with the first communication line by a second communication line, and the differential signal of the first signal is transmitted and received using both the first communication line and the second communication line.

4. The signal processing device according to claim 3, further comprising: a second branch line that branches off at a second branch point in the second communication line located outside the second communication unit and connects to the second communication unit, and transmits the second signal via the portion of the second communication line from the first communication unit to the second branch point; and a second switching unit located near or at the second branch point on the second branch line, which, when communication using the second signal is performed, blocks the propagation of the differential signal of the first signal to the second branch line, and when communication using the second signal is performed, allows the second signal to pass through the second branch line.

5. The signal processing apparatus according to claim 4, wherein the first communication unit and the second communication unit transmit and receive differential signals of the second signal using both the portion of the first communication line from the first communication unit to the first branch point and the first branch line, and the portion of the second communication line from the first communication unit to the second branch point and the second branch line.

6. The signal processing device according to claim 4, wherein the first communication unit and the second communication unit transmit and receive different second signals on the portion of the first communication line from the first communication unit to the first branch point and the first branch line, and on the portion of the second communication line from the first communication unit to the second branch point and the second branch line.

7. The signal processing apparatus according to claim 4, wherein the first switching unit and the second switching unit simultaneously block the propagation of the differential signal of the first signal to the first branch line and block the propagation of the differential signal of the first signal to the second branch line, and also simultaneously allow the passage of the second signal through the first branch line and the passage of the second signal through the second branch line.

8. The signal processing device according to claim 4, wherein the first switching unit and the second switching unit simultaneously block the propagation of the differential signal of the first signal to the first branch line and block the propagation of the differential signal of the first signal to the second branch line, and also enable the passage of the second signal through the first branch line and the passage of the second signal through the second branch line at different timings.

9. The signal processing apparatus according to claim 1, wherein the first switching unit is a switch for disconnecting or connecting the first branch line, and the second communication unit is a switching control unit that controls the switch to disconnect the first branch line when communication using the first signal is performed, and to connect the first branch line when communication using the second signal is performed.

10. The signal processing device according to claim 9, wherein the switching control unit transmits a switch switching signal to the switch for controlling the switching of the switch using the first branch line.

11. The signal processing apparatus according to claim 1, wherein the first switching unit is a switch for disconnecting or connecting the first branch line, the first communication unit includes a switching control unit that, when communication using the first signal is performed, transmits a switch switching signal for disconnecting the first branch line to the second communication unit, and when communication using the second signal is performed, transmits a switch switching signal for connecting the first branch line to the second communication unit, and the second communication unit transmits the switch switching signal received from the first communication unit to the switch for disconnecting or connecting the first branch line.

12. The signal processing apparatus according to claim 1, wherein the first switching unit is an inductor having an inductance that prevents the first signal from passing through and allows the second signal to pass through.

13. The signal processing device according to claim 1, further comprising a capacitor between the first branch point and the second communication unit in the first communication line.

14. A signal processing board comprising: a communication unit that communicates using a first signal and a second signal of different types; a first communication line that transmits the first signal to the communication unit; a first branch line that branches off at a first branch point in the first communication line located outside the communication unit and connects to the communication unit, and transmits the second signal together with the portion of the first communication line from the communication unit to the first branch point on the opposite side of the communication unit; and a switching unit located near or at the first branch point on the first branch line, which, when communication using the first signal is performed, blocks the propagation of the first signal to the first branch line, and when communication using the second signal is performed, allows the second signal to pass through the first branch line.

15. A signal processing method by a first communication unit and a second communication unit that communicate using different types of first and second signals, wherein the first communication unit and the second communication unit transmit the first signal on a first communication line connecting the first communication unit and the second communication unit, a first branch line that branches off at a first branch point in the first communication line located outside the second communication unit and connects to the second communication unit, and the second signal is transmitted on the portion of the first communication line from the first communication unit to the first branch point, and when communication using the first signal is performed, the propagation of the first signal to the first branch line is blocked near the first branch point on the first branch line or at the first branch point, and when communication using the second signal is performed, the signal processing method is performed to allow the second signal to pass through the first branch line.

Images