Keyless entry device

1. A keyless entry device, comprising:

a vehicle-side device provided in a vehicle and including:

a first transmission unit that transmits a request signal;

a first reception unit that receives an answer signal; and

a first control unit that controls the request signal transmitted from the first transmission unit, and performs predetermined control when authentication is successful on the basis of the answer signal received by the first reception unit; and

a portable device including:

a second reception unit that receives the request signal;

a second transmission unit that transmits the answer signal in response to the request signal; and

a second control unit that detects reception intensity of the request signal received by the second reception unit, and controls the second transmission unit so as to transmit the answer signal based on the reception intensity of the request signal,

wherein the first control unit controls the first transmission unit such that the request signal includes a intensity measurement signal portion and a determination signal portion, the determination signal portion having a plurality of sections having different intensity levels,

and wherein the first control unit or the second control unit determines whether or not the request signal is a genuine signal which was sent directly from the vehicle-side device on the basis of a fluctuation in the reception intensity in at least one section of the determination signal portion in the request signal, calculates a rate of change in the reception intensity in each section of the determination signal portion in the request signal received by the portable device, and compares the rate of change in the reception intensity with a threshold value to determine whether or not the request signal is the genuine signal.

2. The keyless entry device according to claim 1 ,

wherein the determination signal portion in the request signal transmitted from the first control unit has at least a first section with an intensity level higher than one half of a maximum intensity level of the request signal and a second section with an intensity level lower than the one half of the maximum intensity level.

3. The keyless entry device according to claim 1 , wherein the first control unit or the second control unit determines the fluctuation in the reception intensity for each section of the determination signal portion.

4. The keyless entry device according to claim 1 , wherein the first control unit or the second control unit determines that the received request signal is not genuine if the fluctuation in the reception intensity in one of the plurality of sections exceeds a predetermined threshold value.

5. The keyless entry device according to claim 1 , wherein the intensity level of the plurality of sections in the determination signal portion gradually increases or decreases section by section in accordance with time sequence of the request signal.

6. The keyless entry device according to claim 1 , wherein the determination signal portion is divided into the plurality of sections each having a predetermined time interval such that the intensity level of the determination signal portion changes at the predetermined time interval.

7. A keyless entry device, comprising:

a vehicle-side device provided in a vehicle and including:

a first transmission unit that transmits a request signal;

a first reception unit that receives an answer signal; and

a first control unit that controls the request signal transmitted from the first transmission unit, and performs predetermined control when authentication is successful on the basis of the answer signal received by the first reception unit; and

a portable device including:

a second reception unit that receives the request signal;

a second transmission unit that transmits the answer signal in response to the request signal; and

a second control unit that detects reception intensity of the request signal received by the second reception unit, and controls the second transmission unit so as to transmit the answer signal based on the reception intensity of the request signal,

wherein the first control unit controls the first transmission unit such that the request signal includes a intensity measurement signal portion and a determination signal portion, the determination signal portion having a plurality of sections having different intensity levels,

and wherein the first control unit or the second control unit determines whether or not the request signal is a genuine signal which was sent directly from the vehicle-side device on the basis of a fluctuation in the reception intensity in at least one section of the determination signal portion in the request signal, calculates a time interval between change points at which the reception intensity of the determination signal portion in the request signal received by the portable device changes more greatly than a predetermined extent, and compares the time interval with a predetermined value to determine whether or not the request signal is the genuine signal.

8. The keyless entry device according to claim 7 ,

wherein the determination signal portion in the request signal transmitted from the first control unit has at least a first section with an intensity level higher than one half of a maximum intensity level of the request signal and a second section with an intensity level lower than the one half of the maximum intensity level.

9. The keyless entry device according to claim 7 , wherein the first control unit or the second control unit determines the fluctuation in the reception intensity for each section of the determination signal portion.

10. The keyless entry device according to claim 7 , wherein the first control unit or the second control unit determines that the received request signal is not genuine if the fluctuation in the reception intensity in one of the plurality of sections exceeds a predetermined threshold value.

11. The keyless entry device according to claim 7 , wherein the intensity level of the plurality of sections in the determination signal portion gradually increases or decreases section by section in accordance with time sequence of the request signal.

12. The keyless entry device according to claim 7 , wherein the determination signal portion is divided into the plurality of sections each having a predetermined time interval such that the intensity level of the determination signal portion changes at the predetermined time interval.

13. A keyless entry device, comprising:

a vehicle-side device provided in a vehicle and including:

a first transmission unit that transmits a request signal;

a first reception unit that receives an answer signal; and

a first control unit that controls the request signal transmitted from the first transmission unit, and performs predetermined control when authentication is successful on the basis of the answer signal received by the first reception unit; and

a portable device including:

a second reception unit that receives the request signal;

a second transmission unit that transmits the answer signal in response to the request signal; and

a second control unit that detects reception intensity of the request signal received by the second reception unit, and controls the second transmission unit so as to transmit the answer signal based on the reception intensity of the request signal,

wherein the first control unit controls the first transmission unit such that the request signal includes a intensity measurement signal portion and a determination signal portion, the determination signal portion having a plurality of sections having different intensity levels,

wherein the first control unit or the second control unit determines whether or not the request signal is a genuine signal which was sent directly from the vehicle-side device on the basis of a fluctuation in the reception intensity in at least one section of the determination signal portion in the request signal,

and wherein the answer signal includes information on the reception intensity of the determination signal portion of the request signal, whereby the first control unit determines if the request signal is the genuine signal based on the information on the reception intensity of the determination signal portion in the answer signal received from the portable device.

14. The keyless entry device according to claim 13 ,

wherein the determination signal portion in the request signal transmitted from the first control unit has at least a first section with an intensity level higher than one half of a maximum intensity level of the request signal and a second section with an intensity level lower than the one half of the maximum intensity level.

15. The keyless entry device according to claim 13 , wherein the first control unit or the second control unit determines the fluctuation in the reception intensity for each section of the determination signal portion.

16. The keyless entry device according to claim 13 , wherein the first control unit or the second control unit determines that the received request signal is not genuine if the fluctuation in the reception intensity in one of the plurality of sections exceeds a predetermined threshold value.

17. The keyless entry device according to claim 13 , wherein the intensity level of the plurality of sections in the determination signal portion gradually increases or decreases section by section in accordance with time sequence of the request signal.

18. The keyless entry device according to claim 13 , wherein the determination signal portion is divided into the plurality of sections each having a predetermined time interval such that the intensity level of the determination signal portion changes at the predetermined time interval.