Method for duplex data transmission between a beacon and a vehicle.

State of the art

p0001The invention relates to a method for duplex data transmission between a fixed beacon to a vehicle unit and vice versa between the vehicle device and the beacon according to the preamble of the main claim. In the known data transmission method, for example, after the passive transponder method, different frequencies are used in downlink and uplink. This multiple frequency channels with corresponding bandwidths are required. Corresponding filter circuits are provided in order to prevent crosstalk to adjacent channels for each channel.

ADVANTAGES OF THE INVENTION

p0002The method and the beacon according to the invention and the vehicle device with the characterizing features of the independent claims 1, 5 and 8 have the advantage that both the downlink and the uplink operation at the same frequency can be used. It is particularly advantageous that the bandwidth required is substantially less and virtually identical antennas can be used with only minor modifications. Since no complicated filter circuits are required, results in favorable manufacturing costs.

p0003The measures specified in the dependent claims, advantageous refinements and improvements of the method or the beacon and the vehicle device are possible. It is particularly advantageous that the data transfer between the beacon and the vehicle device can take place simultaneously, so that more data can be transmitted thereby.

p0004The application of the data transmission according to the passive transponder method is low because of the simple structure of the transponder. Due to the different polarizations of the transmitted signal, there is no disturbing coupling so that advantageously the reliability of data transmission is guaranteed.

p0005A particularly simple embodiment of a beacon device results from the fact that in the downlink mode, a first polarization of the transmission signal and the uplink mode, a second polarization. When the uplink mode the vehicle device can then return the data signal in the second plane of polarization. This advantageously results in a simple structure for the on-board unit, since complex filters are not needed.

p0006Further advantages are found in the description.

drawing

p0007An embodiment is shown in the drawing and explained in more detail in the following description. 1 shows the block diagram of a beacon, Figure 2 shows the block diagram of a vehicle unit and Figure 3 is a circular polarization.

Description of the embodiment

p0008Figure 1 shows a beacon device, briefly called beacon, in which a microcomputer 1 is initially connected to an encoder. 2 The encoder 2 is connected downstream of a modulator 3 and a first amplifier 4th The output of the first amplifier 4 is connected to a first transmission antenna fifth The first transmit antenna is for the first plane of polarization, for example, for the horizontal dispersion of the transmission signal is formed. The beacon further has a local oscillator 6, which is connected via a second amplifier stage 7, with a second transmitting antenna 8 for the second plane of polarization, for example vertical polarization is formed. A receiving antenna 9 is connected to a third amplifier 10th The output of down converter 11 is connected via a baseband amplifier 12 to a decoder. 13 The output of the decoder 13 is connected to an input of the microcomputer first

p0009Figure 2 shows a block diagram for a vehicle device, which is also called OBU (On Board Unit). The vehicle device has a receiving antenna 21 which is connected to a first detector 22nd The receiving antenna 21 is tuned to the frequency and polarization of the first transmission antenna fifth The output of the first detector 22 is connected to a first amplifier 23 through a decoder 24 to the input of a controller embodied as a microcomputer 25th An output of the microcomputer 25 is further connected to a modulator 26, whose output is connected via a second detector 27 with a transmitting antenna 28th The receiving antenna 21 is formed for the first polarization plane and the transmitting antenna 28 for the second plane of polarization.

p0010In the following the operation of this circuit arrangement will be described. Both the beacon and the OBU with its components such as microcomputers, encoder, modulator, amplifier, demodulator and decoder that operate in accordance with the passive transponder method, the skilled artisan, for example, from the publication "Advanced Telematics Inhold Transport" Proceedings of the DRIVE Conference , February 4 - 6. 1991 (page 248 - 268) is known. Both the passive transponder method as well as the individual components must therefore not be further explained. The known components can be used for the inventive method and for the construction of the beacon or the OBU.

p0011In the following the operation of the duplex data transmission between the beacon 15 and the vehicle device 20 is explained according to the passive transponder method. The transmission of data from the beacon 15 to the vehicle unit 20 is normally carried out in the ASK method (amplitude shift keying), that is, the beacon transmits an amplitude modulated signal in the downlink to the vehicle device 20. In this case, the microcomputer 1 produced by encoding a carrier signal at the encoder 2 and the modulator 3, the transmission signal which is then amplified by the amplifier 4th The first transmission antenna 5 sends the generated data signal with the first plane of polarization to the vehicle device 1 20. The vehicle device 20 receives with its receiver antenna 21, which has the same polarization plane as the first transmission antenna fifth After further signal processing by the detector 22, through which the carrier frequency is eliminated, is carried out after the first amplifier 23, the decoding. The decoded data signal is then processed by the microcomputer 25th

p0012Parallel or simultaneously to this process is the beacon 15 by means of the local oscillator 6 is a non-modulated carrier signal (Continuous Wave, CW) signal that is sent amplified via the second transmitting antenna 8 to the second plane of polarization. This CW signal is received by the antenna 28 of the vehicle device 20th For this CW-signal of the microcomputer 25 is initially formed over the second detector 27 required for the OBU operating voltage. By the operating voltage of the further, the microcomputer 25 is activated, and then modulates the received carrier signal with the data contained in its memory. By driving the second detector 27 with a stream of these now come in a different workspace, thereby, the reflection factor of the diode is changed. The data signal thus generated is then transmitted via the antenna 28 with the second polarization plane in the uplink to the beacon 15th The transmitted signal is received by the receiving antenna 9 in the same, second polarization plane and, optionally amplified and mixed back via the return mixer eleventh After processing via the base band amplifier 12 and decoder 13, the decoded data signal is input to the microcomputer 1, and can be evaluated there.

p0013The polarization is implemented by means of the antennas. For the first and second polarization plane two orthogonal polarization modes are generally used:<ul><li>a) In the vertical polarization and the horizontal polarization each complementary polarization is generated by rotation of the antenna about the propagation axis.</li><li>b) The left-handed circular polarization and the right-handed circular polarization can be most easily produced by a so-called 90 ° hybrid: The 90 ° hybrid 30 is a known circuit that divides an input power into two equal output powers that are phase shifted by 90 ° and which are radiated by an antenna 31 (Figure 3). There are also special antennas to generate the circular polarization used.</li></ul>

p0014A typical application for the bidirectional transmission of data on the transponder method is for example the exchange of vehicle data or the debiting road tolls etc.