Communications: directive radio wave systems and devices (e.g. – Radar transponder system – Radar transponder only
Patent
1996-05-31
1998-02-24
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Radar transponder system
Radar transponder only
340928, 455132, 455 541, 455272, 375267, 375259, G01S 1376
Patent
active
057215529
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a transponder, preferably for the bidirectional transmission of data to a fixed station designed as a beacon.
BACKGROUND INFORMATION
A transponder for the bidirectional transmission of data between a vehicle's OBU (on-board unit) and a fixed station (beacon), which works in accordance with the semipassive transponder method, is already disclosed by the publication Proceedings of the DRIVE Conference, February 4-6, 1991, "Advanced Telematics in Road Transport" (pp. 248-268). However, the problem occurs that the range of the beacon's reception coverage, for example, is not able to be restricted precisely enough to one single lane (on the road), so that in an automatic toll ticketing (collection) application, it can happen that the OBU of a vehicle driving in a nearby lane so greatly disturbs the communication of the vehicle driving under the antenna that the tolls are not properly debited.
SUMMARY OF THE INVENTION
In contrast, the advantage of the transponder according to the present invention is that through the automatic feedback control of the signal that is retransmitted (sent back) to the beacon, the attenuation of the signal is so conceived that only a strictly limited range is provided for the signal level arriving at the beacon. The attenuation is so controlled in this case that the attenuation of the signal both from the beacon to the vehicle, as well as in the opposite direction is compensated and, as a result, possible interference from nearby lane areas is suppressed. OBUs situated in the nearby lane are limited accordingly out of the corresponding antenna because of their higher useful signal level and can no longer interfere.
It is also advantageous according to the present invention that the downlink signal is controlled by a first automatically controllable amplifier stage (automatic gain control, AGC). There follows, as a result, a first measurement of the level received. For example, the level can vary due to a dirty (window) pane or because of other influences. The level is measured to find a controlled variable with reference to a setpoint value and to use it as a basis for the automatic (feedback) control.
Another advantage of an embodiment according to the present invention is that the variable found in the first measurement is fed for control purposes to another amplifier stage, which amplifies or attenuates the UPLINK signal with the same factor and the retransmits it to the beacon.
In exemplary applications, the advantageous results according to the present invention are attained when allocating the reception range coverage of a beacon to one lane that only one vehicle is covered by the beacon at a time. As a result, when the transponder is mounted on a motor vehicle, one single vehicle can be covered. This is especially advantageous for the automatic debiting of highway tolls or for checking if vehicles have authorized access.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic illustration of the transmit mode in DOWNLINK according to the present invention.
FIG. 2 shows a schematic illustration of the transmit mode in UPLINK according to the present invention.
FIG. 3 illustrates a block diagram of an embodiment according to the present invention.
FIG. 4 illustrates an example of transition of signals in multiple lanes on a road according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 depicts a motor vehicle 2, which is equipped with an (OBU) "on-board unit" or digital communication with a beacon 4. The OBU 1 works as a transponder 3 and receives the amplitude-modulated signals ASK of the beacon 4 in DOWNLINK.
The transponder 3, as well as the beacon 4 are known from the previously mentioned publication and, therefore, require no further clarification. The transponder 3 has a receiving antenna for receiving data signals and a transmitting antenna 1 for transmitting data signals. When microwaves are used, the antennas 1 constitute a part of the transponder.
FIG. 2 depicts the digital c
REFERENCES:
patent: 5444742 (1995-08-01), Grabow et al.
patent: 5459469 (1995-10-01), Schuchman et al.
patent: 5537672 (1996-07-01), Grabow et al.
"Advanced Telematics in Road Transport", Proceedings of DRIVE Conference, Feb. 4-6, 1991, pp. 248-268.
Bode Friedrich-Wilhelm
Fischer Hans-Jurgen
Ohler Michael
Rossius Hans-Ulrich
Vahle Andreas
Robert & Bosch GmbH
Sotomayor John B.
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