WIRELESS COMMUNICATION APPARATUS AND DISTANCE MEASURING METHOD

• US 20070178837A1
• Filed: 12/11/2006
• Published: 08/02/2007
• Est. Priority Date: 12/21/2005
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Koike, Toru
• Granted Patent: US 7,983,692 B2
• Time in Patent Office: Days
• US Class Current: 455/41.200
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems

Abstract

Proposed is a technique for implementing data communication and distance measurement even in a case where data communication and distance measurement share the physical layer. A wireless communication apparatus includes a radio unit and a distance measuring unit. The radio unit performs communication using a frame that includes at least a data period for transferring data and a beacon period for transmitting a beacon. The distance measuring unit utilizes the beacon period to measure the distance from the wireless communication apparatus to a target object whose distance is to be measured.

Claims

1. A wireless communication comprising:

a radio unit which performs communication using a frame that includes at least a data period for transferring data and a beacon period for transmitting a beacon; and

a distance measuring unit which utilizes the beacon period to measure the distance from said wireless communication apparatus to a target object whose distance is to be measured.

2. The apparatus according to claim 1, wherein said distance measuring unit determines the distance from said wireless communication apparatus to the target object by measuring time from transmission of the beacon from said radio unit to receipt of the beacon by said radio unit owing to reflection by the target object.

3. The apparatus according to claim 2, wherein while said radio unit is transmitting data in the data period, said distance measuring unit calculates distance that is based upon the beacon that has been reflected from the target object.

4. The apparatus according to claim 1, wherein said radio unit transmits a pulse signal having a pulse width greater than zero and less than 1 nanosecond as at least part of the beacon.

5. The apparatus according to claim 1, wherein said distance measuring unit determines the distance to another wireless communication apparatus, which is a target object whose distance is to be measured, based upon time response behavior of the beacon transmitted from the other wireless communication apparatus.

6. The apparatus according to claim 5, wherein said distance measuring unit acquires the time response behavior by applying an inverse Fourier transform to a frequency response characteristic obtained by applying a Fourier transform to an OFDM-scheme beacon transmitted from the other wireless communication apparatus.

7. The apparatus according to claim 5, wherein said distance measuring unit acquires the time response behavior by despreading a direct-sequence-scheme beacon transmitted from the other wireless communication apparatus.

8. The apparatus according to claim 1 further comprising a speed measuring unit which measures relative speed of the target object from amount of temporal fluctuation in distance that has been determined based upon the beacon, which is transmitted periodically.

9. The apparatus according to claim 1, further comprising a transmission power controller which controls transmission power of a radio signal, which is transmitted from said radio unit, in accordance with distance acquired in a room within which said wireless communication apparatus is situated.

10. The apparatus according to claim 1, said radio unit transmits and receives a radio signal having a bandwidth of 500 MHz or greater, or a bandwidth that is 20% of the center frequency or greater.

11. An image sensing apparatus comprising:

a wireless communication apparatus set forth in claim 1;

and

a controller which exercises control in such a manner that information indicating distance to a subject acquired by said wireless communication apparatus and image data representing the image of the subject are transmitted via said wireless communication apparatus.

12. A distance measuring method of measuring distance to a target object whose distance is to be measured, comprising the steps of:

transmitting a radio signal using a frame that includes at least a data period for transferring data and a beacon period for transmitting a beacon; and

measuring distance to the target object by utilizing the beacon period.