Mobile object identification device
First Claim
1. A mobile object identification device for a communication area where information is exchanged between a mobile object and a station comprising:
- an antenna control unit having an antenna disposed at said station for repeatedly transmitting a communication signal-wave, which includes a pilot signal and an interrogatory signal in a portion of a cycle time of said communication signal-wave and an unmodulated carrier-radio-wave through said antenna toward said communication area, and for receiving a responding signal-wave from said communication area in another portion of said cycle time; and
a responder unit mounted on said mobile object for transmitting said responding signal-wave when receiving said pilot signal and said unmodulated carrier-radio-wave subsequently, said responder unit including;
a receiving circuit receiving said unmodulated carrier-radio-wave from said communication area,a control circuit generating a responding data-signal, anda transmitting circuit modulating said unmodulated carrier-radio-wave with said responding data-signal and transmitting a modulated carrier-radio-wave as said responding signal-wave;
whereinsaid antenna control unit comprises;
means for decreasing output power of said antenna to a prescribed level while said antenna control unit is transmitting said pilot signal of said communication signal-wave, said prescribed level being lower than the level of the output power of said antenna while said antenna control unit is transmitting said unmodulated carrier-radio-wave, to thereby decrease said communication area, andmeans for switching said pilot signal to said interrogatory signal when an acknowledgment of said pilot signal is received by said antenna control unit.
1 Assignment
0 Petitions
Accused Products
Abstract
A communication area for an antenna disposed on a toll collection gate and a communication area for a responder unit (IU) mounted on an automobile are arranged to coincide with each other. Communication failure in overlapping areas where a plurality of communication areas are formed in a toll collection area is prevented. When an IU receives a pilot signal-wave, a carrier-radio-wave-signal is subsequently transmitted thereto. The IU modulates the carrier-radio-wave-signal with a responding data-signal and transmits the modulated-carrier-radio-wave as a responding signal-wave. In this system, the output power of the responding signal-wave is attenuated during the round trip of the carrier-radio-wave. Therefore, the output power thereof is decreased from an original level when the pilot signal-wave is transmitted. On the other hand, when other signal waves are transmitted, their output power are restored to the original level, thereby equalizing the power of the responding signal of the IU and that of the communication signals from the antenna. Thus, steady communication is ensured.
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Citations
48 Claims
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1. A mobile object identification device for a communication area where information is exchanged between a mobile object and a station comprising:
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an antenna control unit having an antenna disposed at said station for repeatedly transmitting a communication signal-wave, which includes a pilot signal and an interrogatory signal in a portion of a cycle time of said communication signal-wave and an unmodulated carrier-radio-wave through said antenna toward said communication area, and for receiving a responding signal-wave from said communication area in another portion of said cycle time; and a responder unit mounted on said mobile object for transmitting said responding signal-wave when receiving said pilot signal and said unmodulated carrier-radio-wave subsequently, said responder unit including; a receiving circuit receiving said unmodulated carrier-radio-wave from said communication area, a control circuit generating a responding data-signal, and a transmitting circuit modulating said unmodulated carrier-radio-wave with said responding data-signal and transmitting a modulated carrier-radio-wave as said responding signal-wave;
whereinsaid antenna control unit comprises; means for decreasing output power of said antenna to a prescribed level while said antenna control unit is transmitting said pilot signal of said communication signal-wave, said prescribed level being lower than the level of the output power of said antenna while said antenna control unit is transmitting said unmodulated carrier-radio-wave, to thereby decrease said communication area, and means for switching said pilot signal to said interrogatory signal when an acknowledgment of said pilot signal is received by said antenna control unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A mobile object identification device for exchanging information between a mobile object and a station comprising:
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an antenna control unit having an antenna disposed at said station for repeatedly transmitting a communication signal-wave, which includes a pilot signal and an interrogatory signal in a portion of a cycle time of said communication signal-wave, and an unmodulated carrier-radio-wave through said antenna toward a first communication area, and for receiving a responding signal-wave from a second communication area in another portion of said cycle time; and a responder unit mounted on said mobile object for transmitting said responding signal-wave when receiving said pilot signal and said unmodulated carrier-radio-wave subsequently, said responder unit including; a receiving circuit receiving said unmodulated carrier-radio-wave from said first communication area, a control circuit generating a responding data-signal, and a transmitting circuit modulating said unmodulated carrier-radio-wave with said responding data-signal and transmitting a modulated carrier-radio-wave as said responding signal-wave;
whereinsaid antenna control unit comprises; means for decreasing output power of said antenna to a prescribed level lower than said unmodulated carrier-radio-wave while said antenna control unit is transmitting said pilot signal of said communication signal-wave, said prescribed level being lower than the level of the output power of said antenna while said antenna control unit is transmitting said unmodulated carrier-radio-wave, to thereby decrease said first communication area so that the first communication area of said pilot signal coincides with the second communication area of said responding signal-wave, and means for switching said pilot signal to said interrogatory signal when an acknowledgment of said pilot signal is received by said antenna control unit. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A mobile object identification device where information is exchanged between a mobile object and a station comprising:
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an antenna control unit having an antenna disposed at said station for repeatedly transmitting a communication signal-wave which includes a pilot signal and an interrogative signal in a portion of a cycle time of said communication signal-wave through said antenna toward a first communication area and receiving a responding signal-wave from a second communication area in another portion of said cycle time; and a responder unit mounted on said mobile object for transmitting said responding signal-wave when receiving said communication signal-wave, said responder unit including a circuit for transmitting said responding data-signal as said responding signal-wave;
whereinsaid antenna control unit comprises; means for decreasing output power of said antenna to a prescribed level while said antenna control unit is transmitting said pilot signal of said communication signal-wave, said prescribed level being lower than the level of the output power of said antenna while said antenna control unit is transmitting said interrogative signal, to thereby decrease the first communication area, and means for switching said pilot signal to said interrogative signal when an acknowledgment of said pilot signal is received by said antenna control unit. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48)
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Specification