JP2004215037A - System and method of in-vehicle communication and communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure stable communication by a communication system connecting onboard equipment with improved accuracy of reception processing on the receiving side. <P>SOLUTION: The onboard equipment on the transmission side converts a serial signal for transmission into a parallel signal in a serial/parallel converter 31a, separates the converted signal into a plurality of group signals in a transmission signal processor 31, adds a header signal to the top group signal in a mapping section 31b, lines the signals serially, and maps the signals so that the positive and negative signs of the respective signals appear alternately, and then writes the mapped content into the header signal. A multi-level modulator 31c performs multi-level modulation of the mapped signals, and a signal frame section 31d constructs and outputs a signal frame. The onboard equipment on the receiving side identifies an operation frequency of the transmission side by detecting the frequency of the received signal. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to communication between in-vehicle devices connected by a metal communication line, and embedding an operating frequency component of a transmitting-side in-vehicle device in a signal to be transmitted, so that a receiving-side in-vehicle device performs reception processing in synchronization with a transmitting side. TECHNICAL FIELD The present invention relates to an in-vehicle communication system, an in-vehicle communication method, and a communication device that enable the communication.
[0002]
[Prior art]
Various in-vehicle devices such as a monitor device, a camera device, and a navigation device mounted on a vehicle are incorporated into a high-speed information communication system built in the vehicle. In a high-speed information communication system, communication is performed at a communication speed of several tens to several hundreds Mbps.
[0003]
When the above-mentioned in-vehicle devices are connected in a network via a metal communication line to perform communication at a high speed of several tens to several hundreds Mbps, the frequency of a signal carrier increases and noise is radiated from the metal communication line. Such noise may adversely affect the operation of other in-vehicle devices. Particularly, when communication is performed at 50 Mbps or more, the noise interferes with the frequency band of the FM radio and deteriorates the reception condition of the in-vehicle radio tuner. Further, when the signal carrier is rectangular, noise is easily radiated, and the influence is increased.
[0004]
Further, when the frequency band of the signal carrier is high, crosstalk in which noise of one cable is mixed into the other cable among a plurality of twisted pair cables forming the metal communication line, and time required for transmission / reception processing. The deviation tends to cause a phenomenon called jitter that makes it difficult to carry accurate signals. Therefore, in consideration of such an event, in a high-speed information communication system constructed in a vehicle, it is considered appropriate to use a POF (plastic optical fiber) cable for connecting each vehicle-mounted device.
The connection of the in-vehicle device is also disclosed in Patent Document 1 below.
[0005]
[Patent Document 1]
JP 2002-152244 A
[0006]
[Problems to be solved by the invention]
The POF cable generally has a prescribed curvature at the time of wiring in order to secure stable communication. On the other hand, in a vehicle in which a communication system is constructed, various in-vehicle devices are arranged in a limited space in the vehicle, and a POF cable is laid in the remaining space. Wiring is very difficult. Further, compared to metal communication lines, POF cables are more likely to be disconnected due to pinching or stepping on an operator during a vehicle assembly process, and there is a problem that these disconnection factors must be considered during assembly. .
[0007]
Further, in a high-speed information communication system to which a POF cable is applied, a retrofitting device may be incorporated by a user, and the work of attaching such a retrofitting device may be performed by securing the specified curvature of the POF cable. However, there is a problem that it is difficult to mount the retrofitting device. Furthermore, a communication system using a POF cable requires devices such as photoelectric conversion and light-to-light conversion, which raises a problem that the cost required for system construction increases.
[0008]
On the other hand, in some consumer communication systems, high-speed communication of several tens to several hundreds Mbps is enabled by using a metal communication line by modulating a signal and converting the signal into an analog signal for communication. However, in this communication system, the extent to which the communication band can be compressed by modulation is about one half of the original level, so that the effect of noise radiated in a vehicle equipped with many devices operating in various bands is reliably avoided. However, the degree of compression of the communication band is insufficient, which is a factor preventing such a consumer communication system from being diverted to a vehicle.
[0009]
In addition, when performing high-speed communication, it is necessary to synchronize the receiving process of the in-vehicle device on the receiving side with the operating frequency of the transmitting circuit of the in-vehicle device on the transmitting side in order to reliably perform the receiving process in the in-vehicle device on the receiving side. In addition, there is a problem that the in-vehicle device on the receiving side must perform the receiving process in synchronization with the extreme phase of the analog signal to be transmitted. Further, in the metal communication line, since the amplitude of the signal is attenuated by communication at a high rate, it is necessary to consider the attenuation of the amplitude in order to ensure the reliability of communication.
[0010]
The present invention has been made in view of such circumstances, and by embedding an operating frequency component of a transmitting side in a signal to be transmitted, communication stability in a communication system constructed by connecting on-vehicle devices via a metal communication line. It is an object of the present invention to provide an in-vehicle communication system, an in-vehicle communication method, and a communication device capable of ensuring the communication.
It is another object of the present invention to provide an in-vehicle communication system in which a signal to be transmitted is subjected to multi-level modulation to improve the degree of compression of a communication band as compared with the related art, thereby enabling high-speed communication through a metal communication line.
[0011]
Another object of the present invention is to provide an in-vehicle communication system in which the waveform of a signal to be transmitted is deformed to reduce the amount of noise radiated from a metal communication line and suppress adverse effects on surroundings.
Still another object of the present invention is to provide an in-vehicle communication system in which a more stable communication is ensured by notifying a receiving side of an extreme phase of a signal to be transmitted.
Another object of the present invention is to provide an in-vehicle communication system in which the reliability of communication is ensured by appropriately compensating for the attenuation of the signal amplitude due to communication.
[0012]
[Means for Solving the Problems]
An in-vehicle communication system according to a first aspect of the present invention is a communication system in a vehicle in which a transmitting-side in-vehicle device converts a signal by a D / A converter and transmits the signal, and a receiving-side in-vehicle device converts a received signal by an A / D converter. A generating means for generating a plurality of group signals alternately positive and negative by dividing a serial signal; and an output means for outputting the group signals generated by the generating means to the D / A conversion means, The on-vehicle device includes a frequency detecting means for detecting a frequency of the received signal, and a signal restoring means for restoring a serial signal from the signal converted by the A / D converting means in synchronization with the frequency detected by the frequency detecting means. It is characterized by having.
[0013]
An in-vehicle communication system according to a second aspect of the present invention is a communication system in a vehicle in which a transmitting in-vehicle device converts a signal by a D / A converter and transmits the signal, and a receiving in-vehicle device converts a received signal by an A / D converter. , Dividing means for dividing the serial signal into n-bit group signals (where n is an integer of 2 or more), and adding means for adding an n-bit header signal to the head of the group signal divided by the dividing means. Bit conversion means for performing bit conversion such that the signals connected before and after are alternately positive and negative; writing means for writing the conversion content of the bit conversion means into the header signal; Output means for outputting to the A-conversion means, the reception-side in-vehicle device comprises: a frequency detection means for detecting a frequency of a reception signal; and the A / D conversion means in synchronization with the frequency detected by the frequency detection means. Is converted Characterized in that it comprises a signal restoration unit for restoring the serial signal from the signal.
[0014]
A communication system in a vehicle according to a third invention is characterized in that the adding means includes means for adding the header signal for each group signal obtained by subtracting 1 from n.
[0015]
A communication system in a vehicle according to a fourth invention, wherein the output means is a multi-level modulation means for multi-level modulating the header signal and the group signal to a modulation wave signal, and the modulation wave signal multi-level modulated by the multi-level modulation means. To the D / A conversion means, the signal restoration means demodulating the signal converted by the A / D conversion means into the header signal and the group signal, and demodulating by the demodulation means. Means for restoring a serial signal from the demodulated group signal based on the header signal thus demodulated.
[0016]
The in-vehicle communication system according to a fifth invention is characterized in that the transmitting-side in-vehicle device further includes a deforming unit that deforms a waveform of the modulated wave signal output from the output unit into a sinusoidal curved waveform. .
[0017]
In the in-vehicle communication system according to a sixth aspect, the transmitting-side in-vehicle device further includes a reference wave generating unit that generates a reference wave signal having an extreme value of the same sign in synchronization with a phase at which the extreme value of the modulated wave signal is reached. The receiving-side in-vehicle device further includes phase detection means for detecting a phase at which the received reference wave signal becomes an extreme value, and the demodulation means synchronizes with the phase detected by the phase detection means, It is characterized by comprising means for demodulating into a header signal and a group signal.
[0018]
In the in-vehicle communication system according to a seventh aspect, the transmitting-side in-vehicle device further includes an amplitude reference-wave generating unit that generates an amplitude reference-wave signal for determining the degree of attenuation, and the receiving-side in-vehicle device further includes: Amplitude storage means for storing the amplitude of the wave signal; amplitude detection means for detecting the amplitude of the received amplitude reference wave signal; and the amplitude detected by the amplitude detection means and the amplitude stored in the amplitude storage means. Comparing means for performing comparison, and amplifying means for amplifying a signal received so as to match the amplitude detected by the amplitude detecting means with the amplitude stored in the amplitude storing means based on the comparison of the comparing means. It is characterized by having.
An in-vehicle communication system according to an eighth aspect is characterized in that the adding means includes means for alternately changing the sign of the preceding and succeeding header signals when n is an odd number.
[0019]
In the in-vehicle communication method according to the ninth aspect, the in-vehicle device on the transmitting side converts the signal by the D / A converter and transmits the signal, and the on-vehicle device on the receiving side converts the received signal by the A / D converter. The transmitting-side in-vehicle device, wherein the transmitting-side in-vehicle device divides a serial signal to generate a plurality of alternately positive / negative group signals, and outputs the generated group signals to the D / A conversion means; Is characterized in that a frequency of a received signal is detected, and a serial signal is restored from the signal converted by the A / D converter in synchronization with the detected frequency.
[0020]
A communication device according to a tenth aspect of the present invention is a communication device for converting a digital signal into an analog signal by a D / A converter and transmitting the analog signal, wherein the serial signal is divided into n-bit group signals (where n is 2 The above-mentioned integer), an adding means for adding an n-bit header signal to the head of the group signal divided by the dividing means, and a bit conversion for performing bit conversion so that positive and negative of each of the preceding and following signals are alternated. Means, writing means for writing the conversion content of the bit conversion means into the header signal, and output means for outputting the respective signals to the D / A conversion means.
[0021]
According to the first invention and the ninth invention, the transmitting side divides the serial signal to generate a plurality of group signals which are alternately positive and negative, and transmits the analog signal D / A converted from the group signal, while receiving the signal. By detecting the frequency of the received analog signal, the side can specify the ratio of positive and negative changes of the group signal generated on the transmitting side. Since the rate at which the sign of the group signal changes corresponds to the operating frequency component of the transmitting side, the receiving side can specify the operating frequency of the transmitting side by appropriately scaling the specified rate, and synchronize with the specified operating frequency. Then, by performing the receiving process related to the restoration of the signal, stable communication can be secured.
[0022]
In the second invention and the tenth invention, the transmitting side adds a header signal to the group signal obtained by dividing the serial signal, and converts the header signal into a content converted so that each of the preceding and succeeding signals becomes positive and negative alternately. Since the writing is performed, the transmitting side can embed the operating frequency component of the transmitting side in the transmission signal at the above-described positive / negative changing ratio. Further, the receiving side can specify the operating frequency component of the transmitting side by detecting the frequency of the transmitted signal, and can also determine the operating frequency from the specified operating frequency component.
[0023]
Furthermore, since the transmitted signal also contains the alternately converted contents, the original signal can be reliably restored by restoring the received group signal based on the converted contents, and the communication reliability is also improved. Can be secured. Note that the number of bits for dividing the serial signal can be an integer of 2 or more, and the upper limit depends on the communication capability and required communication speed of each vehicle-mounted device included in the communication system of the present invention, For example, it is preferable to increase the number of bits when the communication capability is high, and to reduce the number of bits when the communication capability is low.
[0024]
According to the third aspect, a header signal is added for each group signal obtained by subtracting 1 from the number of bits of the group signal. Therefore, when transmitting, the number of signals constituting one frame and the number of bits included in each signal are determined. The numbers will be the same. Accordingly, it is possible to prevent each bit for writing the converted content of the header signal from becoming short or excessive, and to efficiently perform communication using the communication band of the metal communication line.
[0025]
If the serial signal is divided into two bits, the header signal and the group signal are continuously connected before and after. Therefore, the bit conversion of each signal is performed by the bit conversion means so that the positive and negative of the header signal and the group signal alternate. Done. Also, when the serial signal is divided into three or more bits, the header signal and the group signal are connected before and after, and the required number of group signals are connected before and after the header signal. The bit conversion is performed so that the positive and negative of the signal and the group signal are alternately performed, and the bit conversion is performed so that the positive and negative of each of the group signals in which the required number continues before and after are alternately performed.
[0026]
According to the fourth aspect of the present invention, since the header signal and the group signal are multi-level modulated into the modulated wave signal, the degree of compression of the communication band can be improved as compared with the conventional art, and high-speed communication can be realized by the metal communication line. Interference with the receiving frequency band can be avoided, and adverse effects due to noise radiated from the metal communication line can be suppressed. In order to further ensure the stability of communication, a header signal and a group signal generated by dividing a serial signal are subjected to bit processing such as gray coding and then multi-level modulation is performed. Is also good.
[0027]
Further, it is preferable to apply pulse modulation such as PAM (Pulse Amplitude Modulation) and PWM (Pulse Width Modulation) to the multi-level modulation.
[0028]
According to the fifth aspect, since the waveform of the modulated wave signal is deformed into a sinusoidal curved shape, the rectangular component of the modulated wave signal is removed, and the amount of noise radiated from the metal communication line can be reduced.
According to the sixth aspect, the transmitting side generates a reference wave signal synchronized with the extreme value phase of the modulated wave signal and transmits the generated reference wave signal to the receiving side, so that the receiving side changes the extreme value phase of the transmitted reference wave signal. By detecting and performing reception processing in synchronization with the detected phase, the phases of the header signal and the group signal included in the reception signal can be specified, and stable reception processing can be realized even when high-speed communication is performed.
[0029]
According to the seventh aspect, the transmitting side generates the amplitude reference wave signal for determining the degree of attenuation and transmits it to the receiving side, so that the receiving side detects the amplitude of the transmitted amplitude reference wave signal and stores the amplitude stored in advance. By comparing with the amplitude of the reference wave signal, the degree of attenuation of the amplitude due to communication can be determined. Therefore, the receiving side can return the amplitude level of the modulated wave signal to the level of the transmission state by amplifying the received modulated wave signal so as to return the degree of the amplitude attenuation to the original level, and the communication reliability is further improved. Can build a system. Note that the amplitude reference wave signal and the reference wave signal related to the phase synchronization determination may be shared, and the determination of the degree of amplitude and the synchronization of the phase may be performed by one reference wave signal.
[0030]
According to the eighth aspect, when the number of bits for dividing the serial signal is an odd number, the sign of the preceding and succeeding header signals is alternately changed, so that the sign of the preceding and succeeding header signal and the group signal can be alternately changed. In addition, the operating frequency component on the transmitting side can be reliably embedded in the signal to be transmitted. That is, when the number of bits to be divided is an odd number, if a header signal of the same code is added, the last group signal included in the previous one frame and the header signal included in the subsequent one frame have the same code. As described above, by making the added header signal alternately positive and negative, the signal to be transmitted can be alternately positive and negative for each signal as a whole, and a component corresponding to the operating frequency can be embedded in the signal.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings showing the embodiments.
FIG. 1 shows an overall configuration of an in-vehicle communication system 1 according to a first embodiment of the present invention. The in-vehicle communication system 1 is built in the vehicle S, and includes on-vehicle devices such as a monitor device 2, a camera device 3, and a navigation device 4.
[0032]
Each of the in-vehicle devices 2 to 4 has two connection connector portions 2a, 2b to 4a, and 4b, and the connection connector portions 2b and 3a, and the connection connector portions 2a and 4a are connected to a UTP (Unshielded Twisted Pair). By connecting the metal communication lines C1 and C2 respectively, the in-vehicle communication system 1 having a tree structure is constructed. The in-vehicle devices 2 to 4 mutually transmit and receive various signals via the metal communication lines C1 and C2.
[0033]
FIG. 2 shows an internal configuration of the monitor device 2 and the camera device 3 connected by the metal communication line C1 in the in-vehicle communication system 1. The monitor device 2 internally includes a multi-level encoding circuit section 20 which is electrically connected to the two connector sections 2a and 2b. The multi-level encoding circuit section 20 has a PHY / LINK corresponding to a physical layer of the system. The circuit section 2c is connected. The PHY / LINK circuit section 2c is connected to a monitor video processing circuit section 2d that performs signal display processing.
[0034]
The multi-level encoding circuit 20 processes the received signal and transmits it to the monitor video processing circuit 2d via the PHY / LINK circuit 2c, and the monitor video processing circuit 2d does not illustrate the transmitted signal. A process for displaying on the screen of the monitor device 2 is performed.
[0035]
On the other hand, the camera device 3 has basically the same configuration as that of the monitor device 2, and includes a multi-level encoding circuit unit 30 electrically connected to the two connector units 2a and 2b, and a PHY / PHY layer corresponding to a physical layer. A LINK circuit section 3c and a camera video processing circuit section 3d for processing a captured video signal are provided. The PHY / LINK circuit section 3c transmits the video signal from the camera video processing circuit section 3d to the multi-level encoding circuit section 30 as a serial signal, and the multi-level encoding circuit section 30 transmits the transmitted signal to the multi-level encoding circuit section 30 for transmission. Performs processing and transmits the processed signal to the outside.
[0036]
The metal communication line C1 for connecting the connection connector 2b of the monitor device 2 and the connection connector 3a of the camera device 3 is composed of two twisted pair wires C1a and C1b. Each twisted pair line C1a, C1b is formed by two signal lines, one twisted pair line C1a is used for transmitting a signal from the monitor device 2 to the camera device 3, and the other twisted pair line C1b is used for monitoring from the camera device 3. Used when transmitting a signal to the device 2. The other on-vehicle devices included in the navigation device 4 and the in-vehicle communication system 1 shown in FIG. 1 also have the same internal configuration as the monitor device 2 and the camera device 3, and include a multi-level encoding circuit unit and a PHY / LINK. It has a processing circuit unit related to its function in addition to the circuit unit.
[0037]
FIG. 3 shows only elements necessary for the multi-level encoding circuit units 30 and 20 when transmitting a signal from the camera device 3 to the monitor device 2. The camera device 3 serving as a transmitting-side in-vehicle device includes a multi-level encoding circuit unit 30, a signal generation circuit unit 36, a transmission signal processing unit 31, a transmission digital filter unit 32, a D / A conversion unit 33, an amplification unit 34, and transmission-side timing. The circuit unit 35 is provided as an element necessary for transmission. Further, the monitor device 2 serving as a receiving-side in-vehicle device includes a multi-level encoding circuit section 20, a clock generation circuit section 26, an amplification section 24, an A / D conversion section 23, a reception digital filter section 22, a reception signal processing section 21, A reception-side timing circuit unit 25 is provided as an element necessary for reception.
[0038]
In some cases, the camera device 3 receives a signal and functions as a receiving-side in-vehicle device. Therefore, the multi-level encoding circuit unit 30 includes the multi-level encoding circuit of the monitor device 2 in addition to the units 31 to 36 described above. A clock generation circuit unit and an amplification unit (not shown) similar to the units 21 to 26 described in the unit 20 are provided. In addition, since the monitor device 2 may also function as a transmitting-side in-vehicle device, the multi-level encoding circuit unit 20 includes a signal generation circuit unit for transmission processing, a transmission signal processing unit, and the like (not shown).
[0039]
When the camera device 3 transmits a digital serial signal related to imaging, the transmission signal processing unit 31 of the multi-level encoding circuit unit 30 performs parallelization of the serial signal, header signal addition, and mapping as shown in FIG. , Important processes related to transmission, such as multi-level modulation and framing. When the monitor device 2 receives a signal, important processes related to reception such as demodulation and inverse mapping of the signal received by the received signal processing unit 21 of the multi-level encoding circuit unit 20 are performed.
[0040]
Therefore, hereinafter, first, the transmission signal processing unit 31 of the camera device 3 and the respective units 32 to 36 around the transmission signal processing unit 31 will be described, and thereafter, the respective units 21 to 26 of the monitor device 2 will be described.
[0041]
FIG. 4A shows an internal configuration of a transmission signal processing unit 31 of the camera device 3, wherein the transmission signal processing unit 31 divides a serial signal to be transmitted and generates a plurality of group signals that are alternately positive and negative. It functions as an output unit that outputs the generated group signal to the D / A conversion unit 33. The transmission signal processing unit 31 converts a serial signal into a parallel signal, a serial / parallel conversion unit 31a, a mapping unit 31b that performs mapping such as conversion of each bit of the parallel signal and addition of a header signal, and performs multi-level modulation of the signal. It comprises a multi-level modulation section 31c and a signal frame section 31d for constructing a signal frame for transmission, and the above-mentioned output means includes the multi-level modulation section 31c and the signal frame section 31d.
[0042]
The serial / parallel conversion unit 31a functions as a dividing unit that divides the serial signal transmitted from the PHY / LINK circuit unit 3c into a group signal of n bits (n is an integer of 2 or more, the same applies hereinafter). As shown in FIG. 6, the serial / parallel converter 31a according to the present embodiment converts a serial signal having consecutive bits such as "1101010111111..." Into a group of three bits such as "110" and "101". The signal is divided into two signals and parallelized.
[0043]
The mapping unit 31b includes an adding unit that adds an n-bit header signal to the head of the group signal, a bit converting unit that performs bit conversion of the group signal so that each of the preceding and succeeding signals is alternately positive and negative, and It functions as writing means for writing the contents of the conversion into the header signal.
[0044]
As shown in FIG. 5, the adding unit of the mapping unit 31b adds n bits to the head of each of the “n−1” group signals for the n-bit group signals divided by the serial / parallel conversion unit 31a. A number of header signals are added. In addition, a group in which one header signal and “n−1” group signals added to the head are combined is constructed as one signal frame having n × n bits by a signal frame unit 31d described later. Is done.
[0045]
The adding means of the present embodiment adds a 3-bit header signal in response to the parallelization of the serial signal into a 3-bit group signal. Are specified (“1” in the figure), and the remaining two bits are undetermined (indicated by x in the figure).
[0046]
Also, the header signal added to the preceding and succeeding signal frames is obtained by alternating the most significant bits with "1" and "0", that is, alternately with the header signals "1xx" and "0xx". Like that. By doing so, the preceding and succeeding header signals are alternately positive and negative as a result of the multi-level modulation by the multi-level modulation section 31c described later. In this embodiment, the header signal to be added first is “1xx”, but the first header signal can be set to “0xx”.
[0047]
The bit conversion means of the mapping unit 31b converts (maps) the most significant bit of each group signal included in each signal frame so that the signs of the header signal and the head group signal are reversed, and the head signal is inverted. The signs of the group signal and the second group signal are reversed. The mapping of the most significant bit of each group signal is performed based on the mapping table of FIG. 7 stored in the mapping unit 31b.
[0048]
Further, the writing unit of the mapping unit 31b refers to the “bit corresponding to the header signal” column of the mapping table shown in FIG. 7 and writes the content of the mapping into “x” of the undetermined bit of the header signal. The mapping content for the first group signal is written to the middle bit “x”, and the mapping content for the second group signal is written to the least significant bit “x”.
[0049]
Specific processing of the bit conversion means and the writing means of the above-described mapping unit 31b will be described with reference to the table of FIG. As shown in FIG. 8A, the header signal is “1xx”, the first group signal as the first group signal as a signal before mapping is “001”, and the second group signal as the second group signal is “1xx”. 011 ”, first, the most significant bit of the first group signal is“ 0 ”, and the most significant bit of the header signal which is the signal before the first group signal is“ 1 ”. 7, the most significant bit of the first group signal after the mapping is designated as “0”. In addition, when such mapping is performed, the bit indicating the mapping content becomes “0” from the mapping table of FIG. 7, and this “0” is written in the middle bit “x” of the header signal.
[0050]
Next, the most significant bit of the second group signal is “0” and the most significant bit of the mapped first group signal, which is the most significant bit of the previous signal, is “0”. The most significant bit after mapping is converted to “1” by the mapping table of “1”. When such mapping is performed, the bit indicating the mapping content becomes “1” from the mapping table of FIG. 7, and this “1” is written to the least significant bit “x” of the header signal. Therefore, the header signal “1xx”, the first group signal “001”, and the second group signal “011” before mapping are respectively converted into “101”, “001”, and “111” by mapping.
[0051]
The multi-level modulation section 31c of the transmission signal processing section 31 shown in FIG. 4A stores the PAM signal generation table shown in FIG. 10 and based on the PAM signal generation table, the mapped header signal and each group signal. Function as multi-level modulation means for performing multi-level modulation on the PAM signal, which is a modulated wave signal.
[0052]
The specific processing of the multi-level modulation unit 31c will be described with reference to the processing of the above-described mapped header signal "101", first group signal "001", and second group signal "111" in the table of FIG. Then, “101” of the header signal is modulated to “3” of the corresponding PAM signal based on the PAM signal generation table of FIG. 10, and similarly, the first group signal “001” is changed to “−5”, and the second The group signal “111” is modulated to “7”.
[0053]
By performing the multi-level modulation as described above, the header signal is positive, the first group signal is negative, and the second group signal is positive, as shown in the graph representing the amplitude for each signal in FIG. The operation frequency component of the transmission signal processing unit 31 is embedded in the signal to be transmitted by alternately switching between the positive and negative.
[0054]
Note that, in order to compare with the above-described processing of generating a positive signal and a negative signal alternately by adding a header signal and mapping by the mapping section 31b, the signal parallelized by the serial / parallel conversion section 31a is not mapped by the multi-level modulation section 31c. An example of multi-level modulation will be described with reference to the table of FIG. 9A and the graph of FIG. 9B.
[0055]
As shown in FIG. 9A, when multi-level modulation is performed on the first group signal “001” and the second group signal “011” to which no header signal is added, based on the PAM signal generation table of FIG. , The PAM signal after multi-level modulation becomes “−5” and “−1”. The PAM signals “−5” and “−1” only show a straight line increasing in the negative region as shown in the graph representing the amplitude for each signal in FIG. Positive / negative corresponding to the component alternately changes and cannot be embedded. Therefore, by performing various processes described above by the mapping unit 31b, the present invention can embed an operating frequency component on the transmission side in a signal to be transmitted and transmit the signal to the reception side.
[0056]
The signal frame unit 31d of the transmission signal processing unit 31 shown in FIG. 4A performs a process of constructing the signal frame shown in FIG. 5 from the header signal of the multi-level modulated PAM signal and each group signal. The signal frame unit 31d constructs a signal frame each time a PAM signal is output from the multi-level modulation unit 31c, passes the constructed signal frame through the transmission digital filter unit 32 shown in FIG. It also functions as a means for outputting the data to the device 33 as needed.
[0057]
The transmission digital filter unit 32 shown in FIG. 3 located on the downstream side of the transmission signal processing unit 31 described above is a roll-off type digital filter, and outputs a PAM signal included in a signal frame output from the transmission signal processing unit 31 as needed. It functions as a deforming means for deforming the waveform into a sinusoidal curved waveform.
[0058]
Since the PAM signal of the signal frame output from the transmission signal processing unit 31 is a rectangular wave 10 including harmonic components as shown in FIG. 11A, the transmission digital filter unit 32 10a is rounded and deformed into a shape shown by a broken line in the figure to obtain a signal 11 having a sinusoidal waveform shown in FIG. By deforming into such a waveform, harmonic components are removed, and noise radiation accompanying the communication of the signal is reduced.
[0059]
The D / A converter 33 shown in FIG. 3 functions as a D / A converter, and converts the transmission digital signal subjected to the various processes described above into an analog signal. The converted analog signal is amplified to a required size by the amplifier 34, and then transmitted from the connector 3a through the twisted pair line C1b. Therefore, the signal transmitted in this manner is compressed at a higher rate by the multi-level modulation than the conventional communication system. Therefore, the band used for communication and the transmission clock are lowered to keep the communication band away from the FM band. . As a result, even when high-speed communication is performed using the twisted pair line C1b, which is a metal communication line, it is possible to prevent the in-vehicle devices from being affected by emission noise.
[0060]
The transmission-side timing circuit unit 35 shown in FIG. 3 controls the operation timings of the transmission signal processing unit 31, the transmission digital filter unit 32, and the D / A conversion unit 33 in a clock-wise manner to control each of the units 31 to 33. Are controlled to perform a synchronized operation.
[0061]
Further, the signal generation circuit unit 36 provided on the upstream side of the transmission signal processing unit 31 synchronizes with the phase having the extreme value of the waveform of the PAM signal shown in FIG. It functions as a reference wave generation unit that generates a wave signal. In the present embodiment, the reference wave signal is also used as an amplitude reference wave signal for determining the degree of attenuation, so that the signal generation circuit unit 36 also functions as amplitude reference wave generation means.
[0062]
The reference wave signal is used for phase synchronization at the time of performing demodulation processing on the signal received on the monitor device 2 side and for determining the degree of attenuation of amplitude due to communication. Note that the reference signal has different extreme values of the header signal and the group signal so that the phases of the header signal and the group signal can be distinguished from the signal received for the phase synchronization. Due to the difference, the phase of the header signal and the phase of the group signal can be determined on the receiving side.
[0063]
The reference wave signal generated in this manner is used when the ignition switch of the vehicle S is turned on and the in-vehicle communication system 1 is started, when the in-vehicle communication system 1 is reset, and when the camera device 3 and the monitor device 2 are connected. The signal is output from the signal generation circuit section 36 when a signal is not transmitted / received between them, and transmitted from the camera apparatus 3 to the monitor apparatus 2.
[0064]
On the other hand, the monitor device 2 shown in FIG. 3 includes the amplification unit 24, the clock generation circuit unit 26, and the like in the multi-level encoding circuit unit 20 as described above, and the amplification unit 24 receives the analog signal received through the connection connector unit 2b. The received signal is amplified to a required size. The clock generation circuit unit 26 functions as frequency detection means for detecting the frequency of the amplified received signal, and multiplies the detected frequency by a required value by a constant to operate in the same manner as the units 31 and 32 on the transmission side. Generating frequency. The clock generation circuit section 26 transmits the generated operating frequency to the reception-side timing circuit section 25 and the A / D conversion section 23.
[0065]
The reception-side timing circuit unit 25 controls the operation of the reception digital filter unit 22 and the reception signal processing unit 21 in synchronization with the transmitted operating frequency. Operates at the same clock as that of the camera device 3 on the transmission side, and can perform synchronized processing on the transmission and reception sides even when high-speed communication is performed, thereby ensuring communication stability.
[0066]
The A / D converter 23 corresponds to an A / D converter, and converts a received analog signal into a digital signal. This conversion process is also performed in synchronization with an operation clock transmitted from the clock generation circuit unit 26. . Further, the reception digital filter unit 22 performs an equalizer-like process, shapes a waveform that is corrupted by communication, and outputs the waveform to the reception signal processing unit 21. The reception signal processing unit 21 functions as a signal restoration unit that restores the original serial signal from the signal converted by the A / D conversion unit 23 and shaped by the reception digital filter unit 22.
[0067]
FIG. 4B shows an internal configuration of the reception signal processing unit 21 and includes a demodulation unit 21a, an inverse mapping unit 21b, and a parallel / serial conversion unit 21c.
[0068]
The demodulation unit 21a functions as a demodulation unit that demodulates a signal that has been processed by the A / D conversion unit 23 and the reception digital filter unit 22 into a header signal and a group signal generated on the transmission side. The demodulation unit 21a also stores the PAM signal generation table shown in FIG. 10, and obtains a 3-bit value corresponding to the extremum at the specified phase in the received signal based on the PAM signal generation table. The header signal and the group signal are demodulated. In addition, the level adjustment unit 21e and the phase synchronization unit 21d included in the demodulation unit 21a are used to specify the phase.
[0069]
The level adjuster 21e adjusts the attenuation of a signal transmitted through the twisted pair line C1b, and a memory (shown in FIG. 1) corresponding to an amplitude storage unit that stores in advance the amplitude of a reference wave signal transmitted by the camera device 3. And functions as amplitude detecting means, comparing means, and amplifying means.
[0070]
The amplitude detector of the level adjuster 21e detects the amplitude of the received reference wave signal, and the comparator compares the amplitude stored in the memory with the detected amplitude. The amplification means of the level adjustment unit 21e adjusts the level of the amplitude based on the comparison so that the detected amplitude matches the amplitude stored in the memory. By thus returning the amplitude of the received signal to the level at the time of transmission, the demodulation accuracy of the demodulation unit 21a is improved and the reliability of communication is ensured.
[0071]
In addition, the phase synchronization unit 21d functions as a phase detection unit that detects a phase at which the monitor apparatus 2 receives the extreme value of the reference wave signal from the camera apparatus 3. That is, the phase synchronization unit 21d detects the phase of the header signal and the phase of the group signal from the different extreme values of the received reference wave signal. Therefore, the demodulation unit 21a specifies the phase of the header signal and the group signal of the signal received in synchronization with each phase detected by the phase synchronization unit 21a, and demodulates the header signal and the group signal from the extreme value of the specified phase. ing.
[0072]
The reverse mapping unit 21b of the reception signal processing unit 21 shown in FIG. 4B generates a group signal before mapping from the similarly demodulated group signal based on the header signal demodulated by the demodulation unit 21a. . The inverse mapping unit 21b stores the mapping table shown in FIG. 7, and generates a signal before mapping by inverse mapping each of the most significant bits of the group signal from the values of the lower two bits of the header signal. The inverse mapping unit 21b outputs only the generated group signal before mapping to the parallel / serial conversion unit 21c, and does not output a header signal.
[0073]
The parallel / serial conversion unit 21c functions as a unit that connects the group signals before mapping generated by the reverse mapping unit 21 and restores the original serial signals. The parallel / serial conversion unit 21c performs a restoration process each time a group signal is received from the inverse mapping unit 21b, and outputs the restored serial signal to the PHY / LINK circuit unit 2c shown in FIG. 2 as needed.
[0074]
Next, a series of processing contents according to the in-vehicle communication method when a signal is transmitted from the camera device 3 to the monitor device 2 in the in-vehicle communication system 1 described above is divided into a transmitting-side process and a receiving-side process. A description will be given based on the first and second flowcharts of FIGS.
[0075]
First, as shown in the first flowchart of FIG. 12A, the camera device 3 generates a reference wave signal that also serves as an amplitude reference wave signal (S1), at the time of system startup of the in-vehicle communication system 1 and at the time of bus reset. The generated reference wave signal is transmitted to the monitor device 2 (S2). Next, the camera device 3 generates a plurality of group signals by dividing the serial signal to be transmitted as shown in FIG. 6 (parallelization), adds a header signal to the generated group signals, and performs mapping and multi-value processing. After the modulation, a transmission signal process of constructing a signal frame (framing) is performed (S3).
[0076]
Further, the camera device 3 modifies the waveform of the modulated wave signal (PAM signal) included in the signal frame subjected to the transmission signal processing (S4), and outputs the signal subjected to the waveform modification to the D / A converter 33. Then, the analog signal is converted into an analog signal (S5), and the analog signal is transmitted to the monitor device 2 (S6).
[0077]
On the other hand, as shown in the second flowchart of FIG. 12B, the monitor device 2 on the receiving side first receives the reference wave signal (S10), and performs phase synchronization of the demodulation unit 21a based on the received reference wave signal. The unit 21d and the level adjusting unit 21e perform a phase synchronization process on the extreme value of the signal received and a process related to the adjustment of the amplitude level of the received signal (S11).
[0078]
After performing the above-described preparation processing, the monitor device 2 receives an analog signal from the camera device 3 through the twisted pair line C1b (S12), detects the frequency of the received analog signal, and generates an operating frequency on the transmission side. (S13) The following processing is performed in synchronization with the generated operating frequency. That is, the received signal is converted into a digital signal by the A / D converter 23 (S14), and the converted digital signal is subjected to signal processing such as demodulation, inverse mapping and serialization to restore the original serial signal. Signal processing (S15).
[0079]
The restored serial signal is output from the multi-level encoding circuit unit 20 to the monitor video processing circuit unit 2d via the PHY / LINK circuit unit 2c, and the video signal of the camera device 3 transmitted by high-speed communication is output from the monitor device 2. Displayed on the screen. The above description is for the case where a signal is transmitted from the camera device 3 to the monitor device 2. However, when the signal is transmitted from the monitor device 2 to the camera device 3, and when other in-vehicle devices of the in-vehicle communication system 1 are transmitted. The same processing is performed when communication is performed between devices.
[0080]
The communication system 1 in the vehicle, the camera device 3 corresponding to the communication device on the transmitting side, the monitor device 2 corresponding to the communication device on the receiving side, and the communication method in the vehicle are not limited to the above-described embodiments, and various modifications are made. Examples can be applied.
[0081]
For example, the present invention can be applied to a communication system formed of a ring type, a star type, a daisy chain type, or the like, in addition to a tree structure communication system. Further, as shown in FIG. 2, the multi-level encoding circuit units 20 and 30 and the PHY / LINK circuit units 2c and 3c are separate units, but both may be made into one chip to reduce the size. .
[0082]
When the communication speed is not extremely high, for example, various processes related to generation of the reference wave signal, reception of the reference wave signal, phase synchronization, and level adjustment can be omitted as appropriate. Further, when the influence of the radiation noise is low due to the arrangement of the on-vehicle equipment, the processing related to the waveform deformation of the signal to be transmitted may be omitted. Further, in the multi-level modulation in the multi-level modulation section 31c, the header signal and the group signal may be modulated into a PWM signal.
[0083]
If it is necessary to further enhance the reliability of communication, gray coding is performed such that only one bit changes according to the value of the header signal and the group signal after mapping by the mapping unit 31b. After the processing, the multi-level modulation section 31c may perform multi-level modulation. In the case where the gray encoding process is performed as described above, a gray encoding processing unit is newly provided between the mapping unit 31b and the multi-level modulation unit 31c in the transmission signal processing unit 31 illustrated in FIG. I do.
[0084]
Furthermore, the serial / parallel converter 31a on the transmission side can also divide the serial signal by an even number of bits other than an odd number. The most significant bit of the header signal added to the signal frame to be added is not alternated with “1” and “0”, but is set to one of “1” and “0”. By doing so, the header signal can reverse the sign of the preceding and succeeding group signals.
[0085]
Furthermore, when the mapping section 31b is divided by an odd number of bits, the transmission signal processing section 131 of FIG. As shown in (1), the first and second switch units 131h and 131i and the mapping unit 131b to the signal frame unit 131g may be provided respectively for positive and negative.
[0086]
The transmission signal processing unit 131 of the modified example switches the first switch unit 131h up and down every time the serial / parallel changing unit 131a parallelizes a group signal corresponding to one signal frame. For example, when the serial / parallel changing unit 131a divides into three-bit group signals, the first switch unit 131h is switched every time two group signals pass.
[0087]
The primary mapping unit 131b, the primary multi-level modulation unit 131c, and the primary signal frame unit 131d arranged on the upper side perform processing on the signal whose most significant bit of the header signal added by the primary mapping unit 131b is “1”. Things. On the other hand, the negative mapping unit 131e, the negative multi-level modulation unit 131f, and the negative signal frame unit 131g arranged on the lower side correspond to the signal whose most significant bit of the header signal added by the negative mapping unit 131e is “0”. Processing is performed.
[0088]
The second switch unit 131i located on the downstream side is switched each time each signal corresponding to one signal frame is processed by the upper units 131b to 131d and the lower units 131e to 131g. By switching the second switch unit 131i in this manner, a signal frame including a positive header signal generated by each of the upper units 131b to 131d and a negative header signal generated by each of the lower units 131e to 131g are converted. The signal frames that are included are alternately arranged, and the positive and negative of each signal output from the transmission signal processing unit 131 are alternately embedded to reliably embed the operating frequency component on the transmission side in the signal.
[0089]
【The invention's effect】
As described in detail above, in the first invention and the ninth invention, a plurality of group signals that are alternately positive and negative are generated and transmitted, and by detecting the frequency of the received signal, The operating frequency component can be specified on the receiving side, and stable communication can be ensured by performing various processes related to reception in accordance with the specified operating frequency component.
[0090]
In the second invention and the tenth invention, a header signal is added to the group signal to convert each signal so that the signal becomes alternately positive and negative, and the converted contents are written in the header signal. Based on the contents, the received group signal can be reliably restored, and communication stability can be further secured.
According to the third invention, efficient communication processing can be performed by adding a header signal to each group signal of the number obtained by subtracting 1 from the number of bits of the group signal.
[0091]
According to the fourth aspect of the present invention, since the header signal and the group signal are multi-level modulated to the modulated wave signal, the degree of compression of the communication band can be improved, high-speed communication can be realized by the metal communication line, and the adverse effect of radiation noise is suppressed. it can.
According to the fifth aspect, since the waveform is deformed into a sinusoidal curved shape, the amount of radiation noise can be reduced.
[0092]
According to the sixth aspect, since the reference wave signal is generated and transmitted to the receiving side, the receiving side can specify the extreme value of each signal, and can perform more highly accurate receiving processing.
According to the seventh aspect, since the amplitude reference wave signal for determining the degree of attenuation is generated and transmitted to the receiving side, the influence of attenuation due to communication using the metal communication line can be reduced.
[0093]
According to the eighth aspect, when the number of bits for dividing the serial signal is an odd number, the sign of the signal to be transmitted can be alternately changed by changing the sign of the preceding and succeeding header signals alternately. The process of embedding the operating frequency component on the transmission side can be performed stably.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an in-vehicle communication system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a connection state between some devices of the in-vehicle communication system according to the embodiment, and an internal configuration of each device.
FIG. 3 is a schematic diagram illustrating a transmission processing configuration of a transmission-side in-vehicle device and a reception processing configuration of a reception-side in-vehicle device;
FIG. 4A is a schematic diagram illustrating an internal configuration of a transmission signal processing unit, and FIG. 4B is a schematic diagram illustrating an internal configuration of a reception signal processing unit.
FIG. 5 is a schematic diagram showing a configuration of one signal frame.
FIG. 6 is a diagram illustrating a signal processing state in a transmission signal processing unit.
FIG. 7 is a chart showing a mapping table.
FIG. 8A is a table showing values before and after mapping and values after multi-level modulation for an example signal to be transmitted, and FIG. 8B is a graph showing amplitudes for each signal after multi-level modulation.
9A is a chart showing values after multi-level modulation for signals to be compared, and FIG. 9B is a graph showing amplitudes for each signal after multi-level modulation.
FIG. 10 is a table showing a PAM signal generation table.
11A is a graph showing a signal generated by a transmission signal processing unit, and FIG. 11B is a graph showing a signal whose waveform has been deformed by a transmission digital filter unit.
FIG. 12A is a first flowchart relating to processing on the transmission side, and FIG. 12B is a second flowchart relating to processing on the reception side.
FIG. 13 is a schematic diagram illustrating an internal configuration of a transmission signal processing unit according to a modification.
[Explanation of symbols]
1 In-vehicle communication system
21 Received signal processing unit
21a demodulation unit
21b Reverse mapping unit
21c Parallel / serial converter
21d phase synchronization unit
21e Level adjustment unit
25 Receiver timing circuit
26 Clock generation circuit
31 transmission signal processing unit
31a Serial / parallel converter
31b Mapping unit
31c Multi-level modulation section
31d signal frame part
32 Transmission digital filter
35 Transmitting-side timing circuit
36 signal generation circuit

Claims (10)

An in-vehicle communication system in which a transmitting in-vehicle device converts a signal by a D / A converter and transmits the signal, and a receiving in-vehicle device converts the received signal by an A / D converter.
Generating means for dividing the serial signal and generating a plurality of group signals that are alternately positive and negative;
Output means for outputting the group signal generated by the generation means to the D / A conversion means,
The receiving in-vehicle device,
Frequency detection means for detecting the frequency of the received signal;
A communication system in a vehicle, comprising: signal restoration means for restoring a serial signal from a signal converted by the A / D conversion means in synchronization with a frequency detected by the frequency detection means. An in-vehicle communication system in which a transmitting in-vehicle device converts a signal by a D / A converter and transmits the signal, and a receiving in-vehicle device converts the received signal by an A / D converter.
Dividing means for dividing the serial signal into n-bit group signals (n is an integer of 2 or more);
Adding means for adding an n-bit header signal to the head of the group signal divided by the dividing means;
Bit conversion means for performing bit conversion such that positive and negative of each of the signals connected before and after are alternated,
Writing means for writing the conversion content of the bit conversion means into the header signal;
Output means for outputting each of the signals to the D / A conversion means,
The receiving in-vehicle device,
Frequency detection means for detecting the frequency of the received signal;
A communication system in a vehicle, comprising: signal restoration means for restoring a serial signal from a signal converted by the A / D conversion means in synchronization with a frequency detected by the frequency detection means. The adding means,
3. The in-vehicle communication system according to claim 2, further comprising means for adding the header signal for each group signal obtained by subtracting 1 from n. The output means,
Multi-level modulation means for multi-level modulation of the header signal and the group signal into a modulated wave signal,
Means for outputting a modulated wave signal obtained by the multi-level modulation means to the D / A conversion means,
The signal restoration means,
Demodulation means for demodulating the signal converted by the A / D conversion means into the header signal and the group signal;
4. The in-vehicle communication system according to claim 2, further comprising: means for restoring a serial signal from the demodulated group signal based on the header signal demodulated by the demodulation means. The transmitting-side in-vehicle device further includes:
The in-vehicle communication system according to claim 4, further comprising: a deforming unit configured to deform a waveform of the modulated wave signal output from the output unit into a sinusoidal curved waveform. The transmitting-side in-vehicle device further includes:
A reference wave generation unit that generates a reference wave signal having an extreme value of the same sign in synchronization with a phase that becomes an extreme value of the modulated wave signal,
The receiving-side in-vehicle device further includes:
A phase detection unit that detects a phase that is an extreme value of the received reference wave signal,
The demodulation means,
The in-vehicle communication system according to claim 4 or 5, further comprising: means for demodulating the header signal and the group signal in synchronization with the phase detected by the phase detection means. The transmitting-side in-vehicle device further includes:
An amplitude reference wave generation unit that generates an amplitude reference wave signal for attenuation degree determination,
The receiving-side in-vehicle device further includes:
Amplitude storage means for storing the amplitude of the amplitude reference wave signal,
Amplitude detection means for detecting the amplitude of the received amplitude reference wave signal,
Comparison means for comparing the amplitude detected by the amplitude detection means and the amplitude stored in the amplitude storage means,
5. An amplifying means for amplifying a received signal such that an amplitude detected by said amplitude detecting means is matched with an amplitude stored in said amplitude storing means based on a comparison of said comparing means. 7. The in-vehicle communication system according to any one of 6. The adding means,
8. The in-vehicle communication system according to claim 2, further comprising: means for alternately changing the sign of the preceding and succeeding header signals when n is an odd number. The in-vehicle communication method in which the transmitting in-vehicle device converts the signal by the D / A converter and transmits the signal, and the receiving in-vehicle device converts the received signal by the A / D converter.
The transmitting-side in-vehicle device,
Generates a plurality of group signals that are alternately positive and negative by dividing the serial signal,
Outputting the generated group signal to the D / A conversion means;
The receiving in-vehicle device,
Detect the frequency of the received signal,
An in-vehicle communication method, wherein a serial signal is restored from a signal converted by the A / D conversion means in synchronization with a detected frequency. In a communication device that converts a digital signal into an analog signal by a D / A converter and transmits the analog signal,
Dividing means for dividing the serial signal into n-bit group signals (n is an integer of 2 or more);
Adding means for adding an n-bit header signal to the head of the group signal divided by the dividing means;
Bit conversion means for performing bit conversion such that positive and negative of each of the signals connected before and after are alternated,
Writing means for writing the conversion content of the bit conversion means into the header signal;
An output unit for outputting each of the signals to the D / A conversion unit.

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