Transponder for vehicle identification device

• US 5,311,186 A
• Filed: 06/04/1993
• Issued: 05/10/1994
• Est. Priority Date: 09/27/1989
• Status: Expired due to Fees

• Current Assignee: Nippon Soken, Inc. (DENSO Corporation)
• Original Assignee: Nippon Soken, Inc. (DENSO Corporation)
• Inventors: Utsu, Jyunshi, Sasaki, Kunihiko, Kodera, Masao
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/071,619
• Time in Patent Office: 340 Days
• Field of Search: 342/44, 342/42, 342/43, 342/46, 342/50, 342/51
• US Class Current: 342/51
• CPC Class Codes: G01S 13/825 with exchange of information between interrogator and responder
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence

Abstract

The invention relates to a transponder for a vehicle identification device in which a radio wave including vehicle information returned from transponders provided in a vehicle is received by an interrogator. The vehicle transponder receives a query radio wave and uses a detection device to generate a previously memorized coded signal train in response to a received wave. The coded signal train varies an amount of bias voltage of the detection device so that a reflection coefficient of the detection device is varied to modulate the reflection wave of the query radio wave and the modulated wave is transmitted back to the interrogator.

Claims

1. A transponder used in a mobile body identification system in which an interrogator generates a query radio wave to a mobile body and receives a radio wave including mobile body information returned from a transponder provided on said mobile body, said transponder comprising:

an antenna for receiving a query radio wave transmitted from said interrogator to activate a code signal generating means and to modulate a signal, and for transmitting a modulated radio wave to said interrogator;

a detection device for detecting said query radio wave received by said antenna and for generating a detection signal;

coded signal generating means for generating a coded signal train output previously stored in response to said detection signal, and

bias controlling means for varying an amount of bias of said detection device in accordance with said coded signal train output and for varying a reflection coefficient of said detection device in accordance with said coded signal train output so that said coded signal train output is returned to said interrogator as a responding radio wave generated by modulating said reflected wave of said query radio wave;

an electric power source controlling means for supplying the electric power to said coded signal generating means when a detection output having a level exceeding a predetermined set level is detected; and

a circuit for eliminating a modulated component modulated by said bias controlling means and which is superimposed on said detection output generated from said detection device to preclude transmitting the modulated wave, such as a second harmonic wave.

2. A transponder for a vehicle identification device according to claim 1, wherein said coded signal train is previously prepared in accordance with an inherent coded signal of a respective transponder.

3. A transponder for a vehicle identification device according to claim 1, wherein said eliminating circuit eliminates an adverse effect caused by said modulated component by detecting said detection output from said detection device, interposed with said modulated component modulated by said bias controlling means, utilizing an enveloped line detecting method.

4. A transponder for a vehicle identification device according to claim 1, wherein said detection device is a Schottky barrier diode.

5. A transponder for a vehicle identification device according to claim 1, wherein said radio wave is a microwave.

6. A transponder provided on a vehicle and used in a vehicle identification device in which information of said vehicle is read by an interrogator utilizing a microwave in a non-contacting transponder, said transponder comprising:

an antenna for receiving a query microwave transmitted from said interrogator,

a detection device including a detection device for detecting said query microwave received by said antenna and a bias terminal to give a bias voltage to said detection device,

a coded signal generating means for generating a coded signal train previously determined with respect to said information as a modulating signal in response to a detection output generated from said detection device and for applying said modulating signal to said bias terminal to vary the amount of said bias of said detection device so as to vary a reflection coefficient of said detection device in accordance with said coded signal train and to modulate a reflected wave of said query microwave with amplitude modulation (AM) in accordance with said coded signal train to return it back to said interrogator through said antenna;

wherein said transponder is further provided with an electric power source controlling circuit for supplying electric power to said coded signal generating means in response to a detection output generated from said detection device; and

wherein said transponder is further provided with a circuit for eliminating a modulated component caused by said modulated signal output from said coded signal generating means and superimposed on a detection output generated from said detection device to preclude transmitting the modulated wave, such as a second harmonic wave, and

wherein said electric power source controlling circuit supplies electric power to said coded signal generating means in response to a detection output with a modulated component thereof being eliminated by said eliminating circuit.

7. A transponder for, a vehicle identification device according to claim 6, wherein said transponder is further provided with an electric power source controlling circuit for supplying electric power to said coded signal generating means in response to a detection output generated from said detection device.

8. A transponder for vehicle identification device according to claim 7, wherein said transponder is further provided with a circuit for eliminating a modulated component caused by said modulated signal output from said coded signal generating means and superimposed on a detection output generated from said detection device and wherein said electric power source controlling circuit supplies electric power to said coded signal generating means in response to a detection output with a modulated component thereof being eliminated by said eliminating circuit.

9. A transponder for a vehicle identification device according to claim 6, wherein said eliminating circuit detects said detection output generated from said detection device to which modulated components caused by said modulated signal output from said coded signal generating means are superimposed by an envelope detection method.

10. A transponder for a vehicle identification device in which information is transmitted between an interrogator and transponders provided on vehicles utilizing microwaves, each of said transponder comprising:

a detector comprising an antenna for receiving a query microwave generated from said interrogator, a detection device, and a bias terminal for biasing said detection device, said detector functioning such that said query microwave received by said antenna is modulated with amplitude modulation (AM) in two conditions such as a reflecting and absorbing condition, a reflection wave of said modulated query microwave is returned back to said interrogator from said antenna as a responding microwave, then said microwave thus received is detected,

a coded signal generating means for outputting predetermined coded signal trains as a modulating signal in response to said vehicle information and varying an amount of bias of said detection device in response to said coded signal train by applying said modulating signal to said bias terminal, whereby a reflection coefficient of said detection device is varied in response to said coded signal train,

a circuit for eliminating modulated components by said modulating signal generated from said coded signal generating means and superimposed on a detection output detected by said detector, from said detection output, to preclude transmitting the modulated wave, such as a second harmonic wave, and

an electric power source controlling means for supplying electric power to said coded signal generating means in response to said detection output, said modulated components thereof being eliminated therefrom by said eliminating circuit to give operating time for said coded signal generating means.