EP0595019A2 - Method and circuitry for the connection of several digital data channels in one transfer channel - Google Patents

Abstract

In this method and arrangement, at least two digital data signals which have different frequencies are superimposed in time on the carrier signal. The superimposed signal is transmitted and received by a receiving device. The receiving device decodes the digital data signals and can supply them separately to corresponding devices for further processing. A preferred use is in the data transition between a motor vehicle and a stationary beacon. The data to be transmitted contain, for example, traffic guidance data or data for calculating road user fees. <IMAGE>

Description

State of the art

The invention is based on a method and a circuit arrangement for connecting a plurality of digital data channels to form a common transmission channel according to the preamble of the main claim. It is known to carry out the transmission of data signals on a data channel at a specific frequency. For the transmission of a further data signal of a data channel, a further transmission channel is required which has a different frequency to the first transmission channel. When many data signals are transmitted at the same time, the difficulty arises that too few free data channels and transmission channels are available. In this case, an electronic search circuit is usually used to find a free available channel on which the desired data signal can still be transmitted. These search circuits are relatively complex. It also depends on chance whether a free transmission channel can still be found.

Advantages of the invention

The method according to the invention or the circuit arrangement with the characterizing features of the independent claims has the advantage that several data channels are combined into a single transmission channel and the data signals can thus be transmitted quasi simultaneously. As a result, fewer transmission channels are required, which increases the transmission capacity. Another advantage is that the data signals to be transmitted can be evaluated largely independently of one another on the receiving side.

The measures listed in the dependent claims enable advantageous developments and improvements of the method or of the circuit arrangement specified in the independent claim. It is particularly advantageous that the proposed method does not prescribe any restriction in the modulation of the data channels, so that the carrier frequency of the data signals can be amplitude or frequency modulated.

It is also advantageous that the data signals can be synchronized in time with a simple clock signal, so that a clear assignment of the signals is possible when the signals are decoded on the receiving side.

If one chooses a multiple of the period of the first data signal for the further data signal to be transmitted, then the separation of the signals becomes very simple and low-loss.

It is also advantageous to modulate the further data signal in the half-bit period in accordance with the biphase / Manchester method, since in this method the signal becomes zero in the arithmetic mean and thus errors in the signal can be easily recognized.

Further advantages and improvements of the invention are presented in the description.

drawing

An embodiment of the invention is shown in the drawing and explained in more detail in the following description. FIG. 1 shows a block diagram of the transmitter and the receiver, FIG. 2 shows the structure of the data generator and FIG. 3 shows corresponding pulse diagrams.

Description of the embodiment

FIG. 1 shows schematically in the form of a block diagram the transmission and reception device according to the inventive method. It is assumed that the structure of a transmitter 30 and a receiver 20 for transmitting binary coded data signals is known, for example, from EP 0 191 019 B1. According to the invention, the transmission side of a device 10 known in this way is now connected in one or more data generators 1, 2, a data channel being assigned to each data generator 1, 2. The outputs of the data generators 1, 2 are connected via data lines 4, 5 to the inputs of a logic stage 3, which links the data signals of the data generators 1, 2 to form an output signal DL3. Commercially available gate circuits 6 (for example AND gates) can be used as the logic stage 3, which combine the added signals to form a new signal. The new signal is modulated in a modulator 8 and emitted together with the carrier frequency of the transmitter via an antenna 7. To synchronize the data generators 1, 2, a clock signal T is provided, which is formed, for example, by the data generator 2 and is applied to a control input of the data generator 1.

schwingt. T1 ist die halbe Periodendauer des Signals. Der Taktgenerator 31 ist mit einem Eingang einer Logikschaltung 32 (Exklusiv-ODER) verbunden, während an einen zweiten Eingang das zu übertragende Datensignal angelegt wird. Am Ausgang der Logikschaltung 32 ist das Datensignal DL1 bzw. DL2 abgreifbar. Dieses Signal wird an die Verknüpfungsstufe 3 geführt. Das verknüpfte Signal DL3 wird über einen Modulator 8 auf die Antenne 7 gegeben.Figure 2 shows the basic structure of the modulator 1, 2. The modulator 1, 2 has a clock generator 31, which with the frequency $\text{f = 1 / (2 x T1)}$

swings. T1 is half the period of the signal. The clock generator 31 is connected to an input of a logic circuit 32 (exclusive OR), while the data signal to be transmitted is applied to a second input. The data signal DL1 or DL2 can be tapped at the output of the logic circuit 32. This signal is led to logic level 3. The linked signal DL3 is applied to the antenna 7 via a modulator 8.

On the receiving side, after a receiving antenna 15 with a demodulator 17 and a decoder 16, one or more filters 11, 12 are switched, which separate the incoming data signal DL3 in accordance with the transmitted data signals. The filters 11, 12 are designed as a bandpass filter or crossover and are known per se to the person skilled in the art. The demodulator 17 is also commercially available. The separate data signals are fed to the inputs of a commercially available decoder 16 on separate lines 13, 14. Depending on the transmission channel on which the receiver 20 is set, only the data signal which is intended for this receiver is decoded.

FIG. 4 shows a block diagram of decoder 16 for decoding the biphase / Manchester code. The incoming data signal DL1 or DL2 on line 13 or 14 is passed via a comparator 41 for signal shaping reasons.

The clock frequency for the BIT period according to FIG. 3 is then derived from the data signal DL1 or DL2. The actual decoding is carried out by two downstream D flip-flops 43, 44, the output signals of which are combined in a logic circuit 45 as a function of the associated clock signal. The decoded data signal DL1 or DL2 is then available at the output of the logic circuit 45.

The receiver 20 is, for example, only designed to receive and evaluate traffic control data. He then decodes only the data of the data signal DL 1 with his decoder 16. Another receiver, on the other hand, can also / or decode the data signal DL 2, which is used, for example, for billing road user charges.

A typical application for the transmission of data signals is bi-directional data transmission between a motor vehicle and a fixed beacon on the road. In this way, road traffic data, road maps or recommended directions of travel can be transmitted from the beacon to the motor vehicle on this transmission path. But navigation data, for example, about the location of the vehicle as part of fleet management are also possible.

In the exemplary embodiment, only one transmission channel is used to transmit the transmission signal DL 3, which, however, was modulated with the two data signals of the data generators 1, 2. The modulation is expediently carried out using the amplitude modulation method (amplitude shift keying, ASK) and / or using the frequency modulation method (frequency shift keying, FSK). These modulation methods are particularly advantageous, since on the one hand a relatively error-free transmission is guaranteed and on the other hand the coding and decoding can be carried out digitally with simple means. It has been shown that the ASK modulation is particularly advantageous in the transmission mode from the beacon to the vehicle (down link mode) and the FSK modulation in transmission mode from the vehicle to the beacon (up link mode).

In addition to the known coding methods, the biphase / Manchester method is preferably provided. Here the signals are composed of two signal elements that are 180 ° out of phase (Conrads, Moderne Kommunikationstechnik, pages 36, 37; or W. Lee, Mobile Communications engineering, pages 342 - 343).

The mode of operation of the method according to the invention and the effect of the circuit arrangement according to the invention are explained in more detail in FIG. In the upper diagram in FIG. 3, the data signal DL1 of the data line 4 is shown. The data signal DL1 works, for example, at a carrier frequency RF of 5.8 GHz. 18 bit periods 1 ... 18 are shown on the time axis, whereby one bit period has the duration 2 x T1. In the first bit period, the carrier signal RF appears in the second half period, while no signal appears in the first half period. This first bit period corresponds to the value logic '0'. Accordingly, the third bit period contains the value logic '1'. In this way, the logic signals '0' and '1' are encoded by the data generator 1 in accordance with the desired information.

ein Vielfaches von der des Datensignals DL1.The diagram of the data signal DL2 is plotted below the first diagram. Here is the period of a bit period according to the formula $\text{2xT2 = 2nxT1}$

a multiple of that of the data signal DL1.

In the exemplary embodiment, the period T2 of the data signal DL2 is 8 times as long as that of the data signal DL1. The coding with logical '0' and '1' values takes place in the same way as for the data signal DL1. If these two data signals are added in logic stage 3, for example with an AND gate 6, then the signal DL3 to be transmitted results at the output of logic circuit 3 according to the third diagram. After modulation with a commercially available modulator 8, this signal is emitted via the antenna 7 and received by the antenna 15. In the receiver 20, the data signal DL1 and the data signal DL2 are decoded again from this signal.

According to the exemplary embodiment, it is provided that the data signal DL1 contains traffic control data, while the low-frequency data signal DL2 can be used for billing road use fees, parking space fees or the like. Corresponding receiving devices can then be used on the receiver side, which process both signals together or can also evaluate them separately. In a particularly advantageous simple embodiment it is therefore possible, without a change on the transmission side, to connect a simple device for billing the road user fee to the receiver. This device then only evaluates the data signal DL2. The data signal DL1 can be evaluated on a further device, for example on a location and navigation device. This device can also be connected to the receiver 20.

Claims (10)

Method for connecting two or more digital data channels of different data rates to a transmission channel of a transmitter, characterized in that the carrier frequency (RF) of the transmission channel with a first data signal (DL1) with a lower data rate with logical '0' and logical '1' values is modulated that a further data signal (DL2) with a higher data rate is keyed in at an existing carrier frequency, that the overall signal (DL3) is transmitted to at least one receiver (20) and that the receiver (20) has means (11, 12) which enable a separation of the different data signals (DL1, DL2) transmitted on the transmission channel. Method according to claim 1, characterized in that the data signals (DL1, DL2) of the data channels are amplitude (ASK) and / or frequency modulated (FSK). Method according to Claim 1 or 2, characterized in that the data signals (DL1, DL2) can be synchronized in time with a clock signal (T). Method according to one of the preceding claims, characterized in that the bit period of the further data signal (DL 2) is preferably an integral multiple of that of the first data signal (DL1). Method according to one of the preceding claims, characterized in that the further data signal is preferably modulated according to the biphase / Manchester method during half a bit period in which the carrier frequency is transmitted. Circuit arrangement for carrying out the method according to one of the preceding claims, characterized in that the transmitter (30) has at least two data generators (1, 2), that the data generators (1, 2) can be synchronized in time by means of the clock signal T, that the outputs of the Data generators (1, 2) are connected to a logic circuit (3) and that the logic circuit (3) contains the modulatable data signal (DL3) to be transmitted. Circuit arrangement for carrying out the method according to one of claims 1 to 5, characterized in that the receiver (20) has a separating means (11, 12) assigned to the data signals (DL1, DL2) to be transmitted. Circuit arrangement according to claim 7, characterized in that the separating means (11, 12) is a crossover or a filter. Circuit arrangement according to one of Claims 6 to 8, characterized in that the circuit arrangement can be used for the transmission of data signals (DL1, DL2) between a motor vehicle and a fixed beacon and / or in the opposite direction. Circuit arrangement according to Claim 9, characterized in that the data signals (DL1, DL2) are transmitted using the semi-passive transponder method.

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