1. Field of the Invention
The present invention relates to a wireless communication device. In particular, the present invention relates to a wireless communication device that transmits and receives data and receives electric power through an electric wave.
2. Description of the Related Art
In recent years, various electric appliances have become widely used and wide varieties of appliances have appeared on the market. In particular, the spread of portable wireless communication devices has been remarkable. As an example, cellular phones, portable televisions, and the like have become very convenient, which is contributed by the improvement in definition of display portions and durability of batteries and by the reduction of power consumption of the wireless communication devices. The portable wireless communication device has a structure in which a rechargeable battery is built-in to secure electric power. As a battery, a secondary battery (hereinafter referred to as a ‘battery’) such as a lithium ion battery is generally used. However, it is necessary for the battery to be charged from an AC adaptor which is plugged into a household alternating current power supply (for example, see Patent Document 1: Japanese Published Patent Application No. 2005-150022).
In recent years, an individual identification technique utilizing wireless communication using an electromagnetic field, an electric wave, or the like has attracted attention as an application of a wireless communication device. In particular, an individual identification technique with the utilization of an RFID (Radio Frequency IDentification) tag, which communicates data by wireless communication, has attracted attention as an example of the wireless communication device. The RFID tag is also referred to as an IC (Integrated Circuit) tag, an IC chip, an RF tag, a wireless tag, or an electronic tag. The individual identification technique with the utilization of an RFID tag has been useful for production, management, and the like of an individual object and application thereof to personal authentication has been expected.
An RFID tag can be classified into two types depending on whether a power source is built into the RFID tag or electric power is supplied from the outside: an active-type RFID tag capable of transmitting electric waves or electromagnetic waves including information on the RFID tag, and a passive-type RFID tag which is driven by conversion of electric waves or electromagnetic waves (carrier waves) from outside to power (as for the active-type RFID tag, see Patent Document 2: Japanese Published Patent Application No. 2005-316724 and, as for the passive-type RFID tag, see Patent Document 3: Japanese Translation of PCT International Application No. 2006-503376). The active-type RFID tag has a structure in which a power supply for driving the RFID tag is built-in and a battery is provided as the power supply. In addition, the passive-type RFID tag has a structure in which power of electric waves or electromagnetic waves (carrier waves) from the outside is utilized as power for driving the RFID tag and a structure without a battery is realized.
USPTO Backgrounds
USPTO Backgrounds