JPH0750619A - Intra vehicle communication system - Google Patents

Abstract

PURPOSE:To make the communication system to be immune against noise, to reduce a wiring amount, to make the power density of signals small and to reduce influence to other equipments. CONSTITUTION:When the various kinds of switches on a control panel 7 are operated, a communication control circuit 10 generates command codes corresponding to signals outputted from the operated switch and outputs base band signals including the command codes to an SS modulation circuit 11. The SS modulation circuit 11 performs spectrum spreading to the inputted base band signals including the command codes and sends them out through a PLI 13 on a power line 1. The signals SS modulated and sent out from the transmission/reception part 6A of another on-vehicle electric apparatus are inputted through the PLI 13 of the control panel 7 to an SS demodulation circuit 12. The SS demodulation circuit 12 demodulates the inputted signals to the original base band signals. The communication control, circuit 10 inputs the demodulated base band signals, analyzes commands and sends out control signals to a function control circuit 7B based on the analyzed commands.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system between devices mounted on vehicles such as buses and railways.

[0002]

2. Description of the Related Art Conventionally, communication between devices mounted on a vehicle such as a bus is usually performed by providing a dedicated line such as RS232C and RS422. However, in the method of providing a dedicated line and performing communication between devices, since it is necessary to connect each device with a dedicated line, there is a problem that the amount of wiring of the dedicated line increases. For example, a bus currently requires 200 to 300 wiring harnesses. Therefore, it is necessary to perform each wiring such as erroneous wiring and check such as disconnection, and as the wiring amount increases, the wiring work becomes enormous.

Therefore, in order to solve such a problem of the dedicated line, a method of utilizing a power line connected to each device has been proposed as a communication method that does not use the dedicated line.

For example, in Japanese Utility Model Publication No. 63-43525, FM
This is a method of sending a modulated signal to a power line. As another example, a method of sending an AM-modulated signal to a power line has also been proposed.

[0005]

The above-described method of transmitting the FM-modulated or AM-modulated signal to the power line is excellent for reducing the amount of wiring in the vehicle, but is weak to noise in the actual use state. The current situation is that it is not practically usable.

The object of the present invention is to resist noise and
An object of the present invention is to provide an in-vehicle communication method that can reduce the wiring amount and the signal power density, and has less influence on other devices.

[0007]

In order to solve the above problems, a communication system for communicating between devices mounted in a vehicle such as a bus according to the present invention using a power line, an in-vehicle power source and a plurality of in-vehicle devices The electric devices are connected to each other via a common power line, and the at least one on-vehicle electric device outputs a spread spectrum modulation means for spreading the base band signal containing the information signal to the power line. An interface for inputting the spread spectrum signal to another on-vehicle electric device via a power line, and demodulating the signal input via the interface into a baseband signal including an information signal. The gist of the present invention is to include a spread spectrum demodulation means.

[0008]

In the invention configured as described above, when the spread spectrum modulation means of the on-vehicle electric equipment spreads the base band signal including the information signal, the frequency band width of the base band signal is spread N times, and the interface is expanded. Is transmitted to the power line that serves as a communication path. Various electric components such as a radio, a destination indicator, a fare indicator, a wiper, a winker, etc. are connected to the electric power line to generate noise having a specific frequency band. It is assumed that the power density of this noise is, for example, N times that of the spread signal. Conventionally, for example, in the case of FM modulation, when communication is performed in the base band and the frequency band of noise matches the frequency band of the base band, a communication error usually occurs and normal communication cannot be performed.

However, according to the present invention, the spread-spectrum signal is received by the on-vehicle electric device on the receiving side through the interface and demodulated with respect to the spread-spectrum signal. The noise is inversely diffused and the power density is 1
/ N.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a communication system between devices mounted on a bus will be described below with reference to FIGS.

FIG. 1 shows the overall construction of this embodiment.
A battery 2 which is a DC power source as an on-vehicle power source is connected to a DC power line (hereinafter referred to as a power line) 1, and general electric components such as a wiper motor 3, a radio 4, and a light 5 are connected through the power line 1. . Further, the power line 1 is connected to a fare display device 6, an operation panel 7, a numbered ticket issuing device 8 and the like, which are in-vehicle electric devices that require information transmission. The fare display device 6 is provided with a display (not shown), and the fare display corresponding to each reference number is changed or updated on the display based on various display control signals. Further, the numbered ticket issuing device 8 prints a predetermined numbered number on the numbered ticket based on the ticket issuing control signal and then issues the numbered ticket.

The operation panel 7 is provided in the driver's seat. The operation panel 7 is provided with various operation buttons, switches and a display (both not shown). And the operation panel 7
By operating the various switches, the power of general electric components such as the wiper motor 3, the radio 4, and the light 5 can be independently turned on and off. By operating various operation buttons on the operation panel 7, various control signals can be output to the on-vehicle electric devices such as the fare display device 6, the operation panel 7, the numbered ticket issuing device 8 and the like. The electrical configurations of these on-vehicle electrical devices are configured as shown in FIG.

Each on-vehicle electric device such as the fare display device 6, the operation panel 7, the numbered ticket issuing device 8 and the like comprises transmitting / receiving parts 6A, 7A, 8A and function control circuits 6B, 7B, 8B.
The function control circuits 6B, 7B, 8B are composed of unique electric circuits for realizing the functions of the on-vehicle electric equipment. These function control circuits 6B, 7B, 8B are designed to input / output various control signals to / from the communication control circuit 10, but the configuration of these unique electric circuits is not directly related to the gist of the present invention. , The description is omitted. Further, for the sake of convenience of description, the transmitting / receiving unit 7A of the operation panel 7 will be described in detail, and since the transmitting / receiving units 6A and 8A of other vehicle-mounted electric devices have substantially the same configuration, the same components are designated by the same reference numerals and description thereof is omitted. To do.

The transmitting / receiving section 7A of the operation panel 7 is a communication control circuit 1
0, SS modulation circuit 1 as spread spectrum modulation means
1. SS demodulation circuit 1 as spread spectrum demodulation means
2 and power line interface (hereinafter, simply P
(Referred to as LI) 13 and.

When various switches on the operation panel 7 are operated, the communication control circuit 10 generates a command code corresponding to the signal output from the operated switch, and the SS modulation circuit 11 receives a command as an information signal. Output the baseband signal containing the code. The SS modulation circuit 11 performs SS on the baseband signal including the input command code.
Modulation, that is, by multiplying the baseband signal by pseudo noise (PN code) such as the longest linear code sequence (M sequence), spectrum spreading is performed, and PLI13
To the electric power line 1 via.

In addition, the transmission / reception units 6A, 8 of other on-vehicle electrical equipment.
The signal that is SS-modulated from A and sent is the PL of the operation panel 7.
It is input to the SS demodulation circuit 12 via I13. The SS demodulation circuit 12 demodulates the input signal into the original baseband signal. The communication control circuit 10 inputs the demodulated baseband signal, analyzes the command, and sends a control signal to the function control circuit 7B based on the analyzed command.

The SS modulation circuit 11, PLI 13 and S
The configuration and operation of the S demodulation circuit 12 will be described in detail with reference to FIG. The SS modulation circuit 11 includes a pseudo noise generation circuit (hereinafter referred to as PNG) 15, a mixing circuit 16, and a clock generation circuit (hereinafter referred to as CLK) 1.
7, a mixing circuit 18, and an amplifier 19.

Then, in the SS modulation circuit 11, the command code from the communication control circuit 10 is the SS modulation circuit 11
Mixing circuit 16 and pseudo noise generated from the PNG 15 of
, And spread spectrum. Next, in order to reduce the DC (direct current) component of this spread signal, P
The same clock as the clock given to NG15
And mixed by the mixing circuit 18.

Further, this signal is amplified by the amplifier (AMP) 19 so as to have sufficient power to be sent to the power line 1 through the PLI 13. The amplified signal is PLI1
It is sent to the electric power line 1 through 3 and is transmitted to another on-vehicle electric device or the like. Another on-vehicle electric device receives the signal transmitted to the power line 1 via the PLI 13.

The PLI 13 connects, for example, a series circuit including a capacitor 21 and a coil 22 to the power line 1 and a coil 2
It is composed of a circuit in which coils 23 and 24, which are transformer-coupled with 2, are used as modulation and demodulation coils. Note that P
The LI13 may have a simple circuit configuration including only a capacitor.

The SS demodulation circuit 12 includes a band pass filter (hereinafter referred to as BPF) 25, an amplifier (hereinafter referred to as AMP) 26, a phase lock loop circuit (hereinafter referred to as PLL) 27, and a clock generation circuit (hereinafter referred to as CLK).
28, pseudo noise generating circuit (hereinafter referred to as PNG) 2
9. Mixing circuits 30 and 31.

In the SS demodulation circuit 12, unnecessary signals are removed from the SS signal that has passed through the PLI 13 through the BPF 25, and the main frequency component of the SS signal, for example, the main lobe passes. Further, this signal is amplified by the AMP 26 and supplied to the PLL 27. The PLL 27 generates a sync signal for synchronizing clocks. Also, C
The LK 28 generates a clock synchronized with the synchronization signal and outputs it to the mixer 30.

The amplified SS signal is mixed with the clock synchronized by the synchronization signal by the mixer 30, and S
Main lobe center frequency of S signal is DC (direct current) or 0
It is set to Hz. Then, the pseudo noise (PN code) generated from the PNG 29 by the clock from the CLK 28
Then, the signal output from the mixer 30 is mixed in the mixer 31 to extract the original baseband signal. Then, this signal is command-interpreted by the next communication control circuit 10.

FIG. 3 shows signal waveforms at points a to j in FIG. The PN signal in this embodiment uses the longest code sequence (M sequence) [3, 1].

FIG. 4 shows the power density in the frequency domain of the waveform of FIG. Now, the operation of the communication system configured as described above will be described. For example, when the display content change switch of the operation panel 7 is operated to change the display content of the fare display device 6, the communication control circuit 10 responds to the switch based on the signal input from the operated switch. The generated display change command code is generated and output to the SS modulation circuit 11. The SS modulation circuit 11 performs spectrum spreading on the input baseband signal including the display change command code and sends it to the power line 1 via the PLI 13. The signal transmitted on the power line 1 includes, for example, a wiper motor 3, a radio 4, and a light 5.
The noise generated by the operation of is superimposed.

The transmission / reception unit 6A of the fare display device 6 inputs the spread spectrum signal to the SS demodulation circuit 12 via the PLI 13. The SS demodulation circuit 12 demodulates the input signal into the original baseband signal. Then, the communication control circuit 10 inputs the demodulated baseband signal, analyzes the command code, and sends a display change control signal to the function control circuit 6B based on the analyzed command code. As a result, the function control circuit 6B changes the display on the display based on the input display change control signal.

When the display change completion signal of the display is inputted from the function control circuit 6B to the communication control circuit 10 in the fare display device 6, the communication control circuit 10 causes the display change completion command corresponding to the display change completion signal. A code is generated and output to the SS modulation circuit 11. The SS modulation circuit 11 performs spread spectrum on the input baseband signal including the display change completion command code,
It is sent to the power line 1 via 13.

The transmitting / receiving section 7A of the operation panel 7 sends the spread spectrum signal through the PLI 13 to the SS demodulation circuit 12
To enter. The SS demodulation circuit 12 demodulates the input signal into the original baseband signal. Then, the communication control circuit 1
0 inputs the demodulated baseband signal, analyzes the command code, and sends a display change completion signal to the function control circuit 7B based on the analyzed command code. As a result, the function control circuit 7B displays completion on the display of the operation panel 7 based on the input display change completion signal.

Similarly to the above, the baseband signal including the command code is spread between the other on-vehicle electric devices in the SS modulation circuit 11 and is output to the power line 1 through the PLI 13. The signal input via the PLI 13 is demodulated by the SS demodulation circuit 12 into a baseband signal.

Therefore, in the present embodiment, even if noise from other electric equipment enters the power line 1, the noise included in the spread band during SS demodulation is diffused and the power density is reduced. Therefore, it is not affected by noise. Further, since the power line can be used as a communication path without any trouble, a dedicated signal line for controlling various electric devices is not required, and wiring work for a vehicle such as a bus can be performed only with the power line.

Further, since the base band signal is also spread in spectrum, the power density of the signal is reduced, and the adverse effect on other electric devices such as a television and a radio mounted on the vehicle is reduced. The present invention is not limited to the above embodiment,
As the spread spectrum method, a direct spread method, a frequency hopping method, a time hopping method, a chirp modulation method, or a combination method thereof can be used without departing from the scope of the present invention.

[0032]

As described above in detail, according to the present invention, even if noise from other electric devices is superimposed on the power line, the power line can be used as a communication path without trouble, so that various electric devices can be controlled. There is no need for a dedicated signal line, and wiring work for vehicles such as buses can be done only with power lines. As a result, the wiring becomes easier and the number of parts can be reduced by omitting the extra signal line.

Further, since the baseband signal is also spectrum-spread, the power density of the signal is reduced, and there is an excellent effect that other electric devices such as televisions and radios mounted on the vehicle are less adversely affected.

[Brief description of drawings]

FIG. 1 is an overall electrical block diagram of an embodiment of the present invention.

FIG. 2 is an electric block diagram of the same main part.

FIG. 3 is a timing diagram showing signal waveforms in each circuit of FIG.

FIG. 4 is a power spectrum distribution chart.

[Explanation of symbols]

1 ... DC power line, 2 ... battery, 3 ... wiper motor,
4 ... Radio, 5 ... Light, 6 ... Fare display device as in-vehicle electrical device, 7 ... Operation panel as in-vehicle electrical device, 8 ... Numbered ticket issuing device as in-vehicle electrical device, 10 ... Communication control circuit, 11 ... Spectrum SS modulation circuit as spread modulation means, 12 ... SS demodulation circuit as spread spectrum demodulation means, 13 ... PLI (power line interface),
15 ... PNG (pseudo noise generating circuit), 16, 18 ... Mixing circuit, 19 ... Amplifier, 25 ... Band filter, 26 ... Amplifier, 27 ... PLL (Phase lock loop), 28 ...
CLK (clock generation circuit), 29 ... PNG (pseudo noise generation circuit), 30, 31 ... Mixing circuit.

Claims (1)

[Claims] 1. A communication system for performing communication between devices mounted in a vehicle such as a bus using a power line, wherein an in-vehicle power source and a plurality of in-vehicle electric devices are connected via a common power line, and at least One in-vehicle electric device is provided with a spread spectrum modulation means for spread spectrum of a base band signal including an information signal, and an interface for outputting the spread spectrum signal to a power line, and the other in-vehicle electric device is provided with the spread spectrum signal. And a spread spectrum demodulating means for demodulating the signal input through the interface into a baseband signal including an information signal. Communications system.