Electronic key system, on-board device, and electronic key

An on-board device configured to be used in a vehicle and to communicate wirelessly with an electronic key, the on-board device comprising:

• a pattern determining section that is configured to sequentially change and determine a variation pattern of electromagnetic wave intensity of a measurement signal, which is to be transmitted with a variation in the electromagnetic wave intensity;
• a request signal generating section that is configured to generate a request signal including the measurement signal added to the request signal;
• at least one LF transmitter that is configured to sequentially transmit the request signal generated by the request signal generating section to change the electromagnetic wave intensity of the measurement signal included in the request signal received by the electronic key according to the variation pattern as determined by the pattern determining section in response to the electronic key communicating wirelessly with the on-board device to receive the request signal;
• an on-board device receiver that is configured to receive a response signal transmitted by the electronic key, in response to the electronic key receiving the request signal and measuring the variation pattern of the electromagnetic wave intensity of the measurement signal included in the request signal;
• and
• a verifying section that is configured to establish verification of the electronic key, based on a reception of the response signal by the on-board device receiver and a determination based on the response signal in response to the variation pattern measured by the electronic key matching the variation pattern determined by the pattern determining section,
• wherein the at least one transmitter includes a plurality of the LF transmitters at different positions in the vehicle,
• wherein one or more of the plurality of LF transmitters is selected to transmit an individual signal component, which has a predetermined transmission power, to be included in the variation pattern of the measurement signal as determined by the pattern determining section, and
• wherein the one or more of the plurality of LF transmitters is selected
• based on the electromagnetic wave intensity, which is indicated by the variation pattern determined through the pattern determining section, and
• based on an arrangement of the plurality of LF transmitters.

An electronic key configured to communicate wirelessly with an on-board device used in a vehicle, the electronic key comprising:

• an LF receiver that is configured to receive a request signal, which is transmitted by the on-board device, with a measurement signal for measurement of electromagnetic wave intensity;
• a measurement unit that is configured to sequentially measure a variation pattern of the electromagnetic wave intensity of the measurement signal included in the request signal received by the LF receiver;
• a key transmitter that is configured to transmit a response signal to the on-board device in response to the request signal, based on a reception of the request signal by the LF receiver and a measurement of the variation pattern by the measurement unit;
• a change signal generating section that is configured to generate a pattern indicator signal, which instructs the on-board device to change and transmit the variation pattern of the electromagnetic wave intensity of a measurement signal;
• and
• a response signal generating section that is configured to generate the response signal including the pattern indicator signal added to the response signal.

An electronic key system comprising:

• an on-board device that is configured to be used in a vehicle;
• and
• an electronic key that is configured to communicate wirelessly with the on-board device,
• wherein the on-board device includes
• a pattern determining section configured to sequentially change and determine a variation pattern of electromagnetic wave intensity of a measurement signal, which is to be transmitted with a variation in the electromagnetic wave intensity,
• a request signal generating section configured to generate a request signal including the measurement signal added to the request signal, and
• an LF transmitter, which is configured to sequentially transmit the request signal generated by the request signal generating section to change the electromagnetic wave intensity of the measurement signal included in the request signal received by the electronic key according to the variation pattern as determined by the pattern determining section in response to the electronic key receiving the request signal;
• wherein the electronic key includes
• an LF receiver configured to receive the request signal,
• a measurement unit configured to sequentially measure the variation pattern of the electromagnetic wave intensity of the measurement signal included in the request signal received by the LF receiver, and
• a key transmitter configured to transmit a response signal to the on-board device according to the request signal, in response to a reception of the request signal by the LF receiver and a measurement of the variation pattern by the measurement unit;
• and
• wherein the on-board device further includes
• an on-board device receiver configured to receive the response signal, and
• a verifying section configured to establish verification of the electronic key, based on a reception of the response signal by the on-board device receiver and a determination based on the response signal in response to the variation pattern measured by the measurement unit matching the variation pattern determined by the pattern determining section, and
• wherein the electronic key further includes:
• a change signal generating section that is configured to generate a pattern indicator signal indicating the variation pattern to be changed, and
• a response signal generating section that is configured to generate the response signal including the pattern indicator signal added to the response signal, and
• wherein the request signal generating section of the on-board device is configured to determine another variation pattern after the variation pattern is changed in accordance with the pattern indicator signal included in the response signal received by the on-board device receiver.